Friday, May 3, 2024

M25XP Damper Plate replacement Pt.5

Day 4 - Lifting the M25-XP Engine

This is the target!
The Universal M24-XP Engine Damper Plate

It connects the Flywheel to the Gearbox input shaft, the springs act a shock absorbers between the engine - a 3 pot diesel - to the Gearbox which likes to have a nice smooth input.

Prior trips to the boat this week involved removing the Starter, Alternator, Heat Exchanger and all of the hoses and electrical connections to the engine as well as the Throttle, Gear Shift and the engine shut of cables. 

Today after getting the boat setup for the engine removal, I disconnected the drive shaft coupling and removing the 4 engine mount nuts that were holding the engine down.

To lift the engine, I put a 4"x4" piece of wood across the cabin companionway just aft of the cabin top winches. Then I setup a 500lb chain hoist from the wooden beam to the engine.

The Beam was just forwards of the center point of the engine lifting line, so as the engine raised off of the mounting bolts, it shifted forwards. I noticed that there was still an electrical ground cable attached to the top of the heat exchanger mounting plate. Also, I had not disconnected the Raw Water discharge hose attached to the Oberdorfer pump.  They were quickly removed.

Now, lifting the engine an inch or so higher, it swung forward clearing the support stingers, this was working out a lot easier than I had imagined.

I had removed the rug from the deck in front of the galley to the Head door but Peggy said to put it back, we'll replace it and it would be better to protect the floor.

Now that the engine was vertically clear of the engine mounts,  I used a heavy hammer to move the support beam forwards thus moving the engine much further forwards.

We had put some puppy pads between the stringers to catch any drips from the open hoses.

With the engine basically out of the 'Engine Bay' I felt a lot better about the process.

Before lowering the engine, we put a square throwable cushion on the rug beneath the engine and lowered the engine so that it sat on the cushion. 

Despite the smile on my face, I was amazed at how grotty the back of the engine appeared. The gear box looks as though it is covered in a thick grime. In fact it was so thick that the white labels indicating the gear lever movements and the type of gear box oil were not even visible - I didn't know they were there until I sprayed the gearbox with detergent and wiped the surface off.

I'm guessing that the spray from the failing PSS late last year was the cause for the grot on the back of the engine and probably the corrosion on the heat exchanger plate.

At this point the engine is out and supported by a 3 line attachment to the chain hoist, It's sitting on the Red cushion but the bell housing nuts and bolts are not removed.

I first slackened the bolts with a manual wrench. Then we cut out a piece of cardboard and made 10 holes in it to hold the bolts. I used the new cordless socket wrench to remove the bolts and nuts from the housing.

As I removed the Bolts we put them into the cardboard and marked the board with the clock position as well as indicating anything special. ie. Some of the bolts screwed into the housing, others were nuts & bolts (N) and other were removed from the front edge of the housing (R) while all of the others were removed from the gearbox side of the housing.

The nuts were put into a separate container.

Once the bolts were removed, the bell housing is still held in place, there is a 'Pin' on the back of the engine that engages with a hole in the bell housing.

The housing is lose but need to be wobbled off of that pin.

I'm guessing the bell housing and gearbox weigh about 15lbs. It was easy to wiggle the housing off of that pin and lower the housing to the cardboard covered floor.

At last! first sight of the Damper Plate.

It's held on by 8 allen key bolts and came off in just a few minutes.

As soon as it was off we could get a close look at it's condition.

There was very little damage to the plate however, the springs do rattle around in there holders and the edges of the spring holders were showing ware.

Shaking the damper plate we could clearly hear the springs rattling and my understanding is that there should be no movement of the springs within the plate.

Ok, time to clean up and get the replacement.

I had reached out to TMI in Fort Lauderdale whom had confirmed they probably had the replacement plate in stock.  So, let's head down there.

We needed to lockup the boat. The engine was sitting on the cushion and was pretty stable but I wanted to remove the chain hoist. Lowing the engine so that the weight was off the hoist, I was able to lean the engine onto the side of the engine bay portside bulkhead.  Then I could remove the hoist.

We put all of the tools away, locked up the boat and headed to TMI.

Once we found TMI, GPS was not a big help but a phone call to them was answered by clear spoken lady and she gave us directions.

In the store they quickly found the new plate, it's identical and does not rattle!!!

With the new plate in hand and my credit card $133.75 lighter, we headed home to clean up.

Today was a good day! 

Wednesday, May 1, 2024

M25XP Damper Plate replacement Pt.4

Day 3 - Temporary Engine Stand

As mentioned, the plan is to hoist the engine on our next trip down to the boat ( Should be Thursday May 2nd 2024 ) and then move it forwards to provide easy ( Ha! it's a boat! ) access so that we can remove the bell housing and then remove the Damper Plate on our Universal M25-XP 3 pot diesel engine.

I'm going to make a couple of engine blocks ( to act like stringers ) to support the engine when it's out of  it's normally comfy engine room ( Ok, so the engine sits beneath the companionway steps = Engine room )

Basically they will be made from two pieces of 4"x4" wood for a base and then additional 4"x4" blocks on top to support the engine mounting feet, this way the engine should be high enough from the cabin floor so that the sump does not sit on the floor and solidly enough that I can work on the engine.  

The plan is to disconnect the prop shaft coupler from the back of the gear box, then with a line through the two lifting eyes on the top of the engine, I'll use a chain hoist to life the engine ( 1/4Ton hoist > 300lb engine )  Then when the engine is above the level of the top of the engine mount bolts, I'll drag the support beam that is resting on the rails alongside the cabin companionway hatch so that we ( Peggy & I ) can lower the engine onto the temporary engine blocks.

At least, that's the theory.

Once on the blocks, I'll detach the bell housing ( it will still be connected to the Gear Box ) 


After continuing my research about how to change out the Damper Plate, I found that the aft feet of the engine that connect to the motor mounts are not attached to the engine block but are attached to the bell housing ( or Flywheel Housing as it is known in the USA ) 

That means that when I separate the Flywheel Housing from the engine block, the engine will not be supported at the back end and the gearbox & Flywheel housing will not be supported at the front end.


Ok, how to deal with this.

I cannot leave the engine suspended as that means we'll be unable to easily get out of the boat - the companionway will be blocked by the Chain Hoist and support beam, it's asking Peggy a lot to get out via the V-Berth hatch - not easy even when the V-berth is empty  - it's not! All of the gear that was in the Aft cabin is now piled up on the salon seating and in the V-Berth.  

Searching the web, one owner used a fender to support the engine. Another owner used a block to support the front of the flywheel housing when it was detached from the engine block.

Not sure how this is going to work out but instead of making temporary mounting beams I'll try the fender process.

Now I'm thinking that if I lift the engine with the chain hoist and beam across the companionway, then there should be enough  room to move the separated flywheel housing astern over the top of the propshaft coupling.

If I can do that, then I could remove the bolts that hold the flywheel housing to the engine block and lower the gear box and housing onto a fender, even enough to slide it to one side in order to access fhe  flywheel and damper plate. Next I could remove the damper plate, reattach the flywheel housing and put the engine back on it's mounts. When I get the new damper plate, repeat the process but this time installing the new damper plate.

Sounds like a plan.

It's going to be a tough squeeze, but I think I can access the flywheel housing bolts from the aft cabin and with the engine raised on the hoist, I should be able to do this.

So now I'm going to take a few pieces of 2"x4" wood to use as supports and also a 2nd hoist to take the weight of the flywheel housing. I have a small fender onboard and a hand pump so that I can deflate it before putting it under the flywheel housing and then inflate it to where I need it.

The downside of this is that it does not give me the access I was hoping for in order to clean up the engine and give it a bit of love.  

We'll see how it goes.

Tomorrow !! 

Oh, I did order some new material to replace the grotty pieces that the heat exchanger was mounted upon, that should brighten up the back of the engine.

And, as I'll be working on the flywheel with all of it's bolts a couple of times ( 10 bolts ) I indulged in a new cordless rachet tool.

It arrived less than 3 hours from when I ordered it. Both batteries are now charged up and it's ready to go.

Tuesday, April 30, 2024

M25XP Damper Plate replacement Pt.3

 Day 2 - Engine disconnection

Continuing with the engine disconnection process on Day 2.

Again, we limited out time at the boat to 3 hours and only just went over that limit, however, we got a lot done.

Removed the Alternator. That involved removing the Serpentine belt and disconnecting the +ve lead that connects the Alternator to the Main ( LiFePo4 ) batteries. I shut the Solar system down and then turned the master battery switch to off, disconnected the alternator cables, insulated the Main +ve lead and then turn be master battery switch on and then the Solar breaker. Also detached the Alternator Temperature sensor from the -ve connection.

Detached the Exhaust. It just took a gentle tap with a flat head screw driver and the exhaust easily parted from the exhaust manifold.

Detach the fuel hoses: Mindful that they would be full of diesel fuel, we had a disposable cup handy. The hose clamps that secure the hoses to the Primary Fuel Filter housing and the hose from the Injector return fitting were badly damaged by poor quality hose clamps, the perforations have left extremely deep cuts into the hose rubber. I'll replace them with embossed hose clamps when I put the engine back in place.

Detach the engine ground wire from the bell housing. It is held in place by one of the bolts that connect the bell housing to the backplate of the engine.

Detach the Coolant Thermostat temperature sensor and alarm from their housing.

Detach the Starter motor & Solenoid. This involves removing the starter cable ( which connects to the Stater battery ) The Solenoid cable There's also the cable that was used for the original 'Amp' meter on the control panel. It was easy to remove the two bolts that secure the starter by using two socket extensions to reach from in front of the engine back to the starter bolts.

Detach the Oil pressure switch connection. Easy using a short screwdriver.

Detach the Glow Plug power connection.

That pretty much detached everything that needs to be off in order to lift the engine.

My plan for the next part is to lift the engine out of it's normal position and move it forwards so that it can be rotated in order to work on removing the Bell housing. That will provide access the flywheel and the Damper Plate - the reason for doing all of this.

While the engine is out, I'll take the time to service the exterior of the engine, clean it up and apply some fresh engine paint. I'll also replace the primary fuel filter.

Not working on the boat tomorrow ( Wednesday 5/1/2024 )
Plan for Thursday: Protect the floor in front of the engine bay ( I know, that's pushing the concept of 'Engine Bay' :) ). I'll build a temporary engine mount in order to lower the engine. I'll use a simple 4"x4" beam with an additional piece of 4"x4" just bigger than the engine mounts.

That should provide plenty of room to get around the engine but also, it should allow me to remove the chain hoist used to lift the engine so that I can get out of the boat via the companionway.

I'll make the beam tomorrow ( Wednesday )

M25XP Damper Plate replacement Pt.2

The Plan for changing the Damper Plate

Today ( Monday April 29th ) we went down to the boat with the intent on figuring what and when we will work upon. I spent a few minutes reviewing the engine and making the plan. I'm only going to work for 3 hours each day, no point in exhausting myself and will make better progress too.

Remove the Heat Exchanger. That's 4 hoses ( I should have drained the coolant before disconnecting those hoses ) and two large hose clamps that secure the heat exchanger to it's mounting plate.

Disconnect the Throttle Linkage and Engine Shutoff link from the engine. Disconnect the gear shift cable from the gear box.

Remove the 4 engine mount top nuts.

Remove the 3 bolts that hold the exhaust pipe fitting to the exhaust manifold.

Replace the gear shift cable clamp securing screws with a matching pair of nuts and bolts so that they can be easily manipulated using a wrench and rachet socket instead of trying to hold a screwdriver on one end.  Grrr. ( worse, the two screws were a mismatched one longer than the other and one a flat head screw the other a Philips head screw ) 

Remove the heat exchanger mounting plate and clean it up, it's corroded - look for the cause.

In order to remove the stud bolts that secure the exhaust fitting to the manifold, put on a second nut and lock with the one already on the bolt, then use a wrench to unscrew the stud.

Change the Zink on the heat exchanger while it's out.

Plan for Day 2: 

Remove the Alternator, disconnect and isolate the power cable, disconnect the alternator field connection plug. Disconnect the grounding cable from the engine block and disconnect the prop.





Monday, April 29, 2024

M25XP Damper Plate replacement

Replacing the Damper Plate on our Universal M25XP engine.

After replacing the Engine Motor Mounts on Eximius' Engine, the noises from the engine also changed. I spent several hours working on the Alignment of  the engine to the Prop-Shaft, the noise from the engine at about 1200-1400 RPM was not normal. The propulsion system has always had a sweet spot throttle setting where the vibrations were minimum but now the sound was so bad that I would not feel comfortable even motoring to the end of the canal.

I called a buddy that had told me of a similar situation on  his boat a year or so ago and he graciously gave me the contact info of the mechanic that solved his issue ( alignment ).

When I called 'Greg' he responded that he could meet me at the boat at 11:00 today, WOW! anyone in South Florida knows that if a boat mechanic responds like that then you get your butt in gear!

Greg was at the dock before me and I was early - this is a really good sign.

Once aboard, we discussed previous work I have done on the engine:- Replaced the motor mounts 8 years ago, had the Injector pump rebuilt by RPM a local company, new injectors at the same time and new fuel lines from the pump to the injectors, replaced the Alternator and installed a Serpentine Belt system and External Alternator Regulator, installed a PYI PSS ( shaft seal ) and done an engine alignment, Oil and Filter changes every 50 hours of engine run time. Completely new control panel engine harness wiring.

It was time to flash up the engine. I opened the raw water thru hull valve and heated the Glow Plugs and Started the engine - she started right away.

Greg had me change the throttle settings and gear shift position a few times and increasing the RPM until the noise occurred. During this time, Greg watched the engine and felt various parts giving the engine a lot of attention.

The good news. His opinion of the engine was positive, no excessive vibration but the noise was definitely an issue that should be dealt with promptly. Greg discussed the consequence of the 'Damper Plate' failing and how it could do significant damage to the engine &/OR gearbox. So, I'm on it.

Greg provided me with the contact of a local company that probably has the Damper Plate in stock. 

We shared a few stories about our similar backgrounds in the Navy aboard Aircraft Carriers, his time aboard ending before mine began in 1964. 

I called the company and found that they do have 3 types of damper plate in stock and the best thing to do was to bring the plate from the boat to them and they would confirm which one to use.

Greg advised that the Damper Plate should probably replaced every 1500 hours. Eximius has about 7,000 hours and is 37 years old, that comes down to about 200 hours a year. We do that easily! probably more.

So, we're going to replace the Damper Plate.

Tuesday, March 5, 2024

Adding Aqua Maps to our Navigation System

Upgrading our Navigation System with AquaMaps

Our Navigation System is pretty good, but I wanted to add some redundancy. Yes we have Chart Books for our sailing areas, I just like to be prepared.

Here's our Current Nav Electronics Inventory.
  • Garmin 741XS Chart Plotter
  • Garmin DST 810 Depth, Speed, Water Temperature Transducer
  • Garmin GMR 18" Radar
  • Garmin GWind Wind Transducer
  • Garmin GMI Display 
  • Raymarine EVO 100 Autopilot 
  • EmTrak AIS Transceiver
On a recent trip from Lake Boca to Port Everglades, the Garmin 741xs Chartplotter had an episode, didn't want to play. So we rebooted it. That's when it failed, would not boot up. At the time we were just North of the Hillsboro Inlet which is notorious for shoaling. Our 5'8" draft means we have to avoid those shoals, so monitoring our Depth is a must. With the Chartplotter not functioning, we had to rely upon the GMI display to show our depth. It could do this because all of our Electronics are on our NEMA2000 Network. and the DST 810 is also a NEMA2000 device. Hence we were able to monitor our depth as we went out of the HI inlet, whew!

Once outside on the Ocean, we switched everything off for a minute and turned it all back on. The chartplotter woke up and we were back in business.

But what if our Chartplotter failed and would not reboot!  Well, we have a 10" tablet with Navionics and Aquamaps, so we could continue navigating. However, they do not display AIS data so we do not know what the other boats around us are doing. Our Radar only displays on the Chartplotter, so we would be out of both AIS and Radar.

Aquamaps has an interface to connect with a WiFi server but it is not compatible with our Garmin Products, only with NEMA 0183 and all of our gear is NEMA 2000.

I searched the net and thought I had found a solution. Digital Yachts make a lot of electonics products for interfacing boat systems. An email to them resulted in a solution.

Digital Yachts NAVLink2

This is a neat piece of electronics.
Basically it's a NEMA 2000 WiFi Server that translates all of the NEMA 2000 Data to NEMA 0183 and delivers it via a WiFi Server.

The best part is that it works for Aqua Maps. In fact, visiting the Digital Yachts website they have the instructions for interfacing with NAVLink2 to Aqua Maps and it's the first App on their list.1

So this should mean that I'll be able to connect Aqua Maps to my NEMA2000 network and receive the Wind, Depth and AIS data.
Thus it will all be available on my Tablet or Phone!

Now if my Chartplotter fails, we will still have the majority of the Navigation data displayed on the Tablet!

Installing the Digital Yachts NAVLink2 

This should be a breeze. The unit gets it's power from the NEMA2000 Backbone, so there is only one electrical connection to make. Simply add a new NEMA2000 'T' onto the backbone and then connect the NEMA2000 Drop cable from the NAVLink2 Server to that 'T'. 

The Instructions for the install are that simple, but if you want to customize the setup, then a Laptop could connect to the NAVLink2 Wifi and access the built in webserver to make any changes required.

Of course, Digital Yachts has all of the details on their website. They also have very clear instructions for connecting the Tablet with Aqua Maps to the NAVLink2 server and setting up which data to display.

I had several emails back and forth with the customer support at Digital Yachts ( I'm pretty sure they are in England ) and they were very polite, clear and obviously know what they are talking about.  I'll provide the links at the bottom of this post.

Mounting the our Samsung FE 7 Tablet ( 10" ) 

Ideally, our Samsung Tablet would be mounted at the Helm with the option to relocate it to the Cabin. I purchased some RAM mounts to accomplish this.

This is the Mount. It allows for the Tablet to be held across it's short side but can be rotated so that it is mounted vertically, that's ideal for the Aqua Maps App.
However, this mount on it's own would place the Tablet in front of our Chartplotter. I would rather it be higher than the top of the Chartplotter and not obscure our view when at the helm

The best solution seems to be to extend the RAM mount so that it can be mounted to the back of the Nav Shelf at the helm and positioned above the Autopilot control panel.

I'll bolt the lower part of the RAM mount to the shelf.

This is a RAM extension. It provides a wide choice of locations for the Tablet and will extend the Tablet above the Nav Shelf and the Autopilot control panel.

The Lower end of this extension will fit on the Ball that is getting bolted to the Nav Shelf.

To join the top of this unit with the RAM mount that is detached from the Bottom of the piece shown above to the piece that holds the Tablet, requires another Ball unit.

This is the missing link ! 

Now all three pieces can be joined together.

I was a bit concerned about the rigidity of the combined pieces, but they are fine.   I now have a spare of the missing link because the package from Amazon contained two pieces. 

Will probably purchase another base unit so that I can set the Tablet on a shelf in the cabin to have eyes on our Navigation from down below.

The end result:

Wow! I mounted my Samsung Tab 7 Tablet at the helm using the mount and RAM joints as planned. The display at the helm is fantastic,

The vertical position is not so clever so I moved it to be Horizontal and level with the top of the chart plotter. Much better.

The screen is bright enough that I can see it clearly even when wearing my prescription sunglasses.

The picture shows us at Anchor in Sunrise Bay Florida.

Peggy suggests that I get a smaller Tablet, it's a 10" display compared to the 7" Garmin 742xs. I tend to agree but wonder if an alternative Tablet will have the brightness of the Samsung Tab 7.

This was the first time that we have used Aqua Maps to follow a route. It provides the distance and the bearing to the next waypoint on the route, very clear.

We do have a couple of issues with the NavLink2 but they are minor and I'm hoping that Digital Yacht can resolve them.

This is a screenshot of the AIS List on Aqua Maps, there is spurious text data on either side of the vessel names. The rest of the information appear correct when we compared it with the AIS data on our chart plotter. 

The list is IMHO easier to figure out on Aqua Maps. 

I'll take more screen shots next time at the boat to display more of the AIS features.

In the Aqua Maps WiFi settings the list of connections shows which data items are connected.

Here you can see that GPS data is Off - that's as I set it because I wanted to see that everything else worked if our Main GPS Chartplotter was down. I turned it off.

The depth data is being supplied by our NEMA 2000 DST 810 Depth, Speed, Temperature transducer.

Heading is being provided by our Raymarine EVO 100 Auto Pilot compass header.

Wind Speed & Direction is provided by our Garmin GWind Wired Transducer on the Mast head.

The AIS data is being provided by the EmTrac AIS unit.

This screen shot of Aqua Maps while we are at Anchor in Sunrise bay.
On the left is the data provided by the NavLink2.

Several people asked me how the NavLink works and my simple reply is 'Magic' !!!  

However here's what it does.

The NavLink2 is connected to the NEMA2000 back bone via a drop cable which is attached to the NavLink2. All I had to do was remove the NEMA2000 Terminator on the end of the backbone, connect a new T connector to the backbone and reconnect the Terminator to the other end of the T. Then connect the NavLink2 NEMA cable to the T - All done.

Then I turned on our Nav Instruments circuit breaker which powered the NEMA 2000 network. I turned on the Garmin Chartplotter so that I could disable the AIS alarm then turned on the EmTrac AIS system.

With the Nav equipment all running, it was time to connect the Tablet to the NavLink2 WiFi Server.

On the Tablet I turned on WiFi and looked for the NavLink2, found it and provided the password. 

At this point I expected the NavLink2 'Status' lamp to change from Flashing Green to Steady Green but it did not happen.

After reading the advise on the Digital Yacht website I rebooted my tablet to make sure no other wifi apps were hogging the system.

Once rebooted and reconnected the WiFi to the NavLink2, I tried to connect Aqua Maps. There's a very clear set of instructions on the Digital Yacht website on how to make the connection. That worked.

Now the List of connections shows up on Aqua Maps.

So that brings us up to date. I'm waiting for a response from Digital Yachts about the flashing status light and the odd chars on either side of the vessel names.

In a nutshell: NavLink2 gets the NEMA2000 data and converts it to NEMA 9183 and transmits it on WiFi, Aqua Maps receives the data via the WiFi on the tablet and displays the selected data on the Aqua Maps App.

Or, as I said earlier - Magic!

See you on the water.


Response from Digital Yacht.
Seems I have a newer model and the Flashing Status lamp is normal. so cross that one off.

They have asked for details about the unit ( firmware version etc. ) So I have to go down to the boat in the next couple of days to get that info. But so far I'm impressed with their post sales support.

For now it's Back to work.


March 23rd 2024.

It has been a busy few weeks and I have not gotten down to the boat in order to respond to DY's questions.  But I did get down today to check on the boat after the rain storm yesterday.  Didn't get to check on the Firmware version. So it'll have to wait till next weekend. I have a bundle of work to do and finish by April 1st which was just moved forwards to being completed by March 29th. So no trips to the boat this week.

Thursday, January 4, 2024

Replacing our Hot Water Tank

Replacing our Seaward Hot Water Tank

Our Hot Water Tank was leaking when we pulled Eximius out of the water at Playboy Marine in Fort Lauderdale. Was it the piping or the Tank?

I Could see water dripping from the front bottom edge of the tank ( The face where the heating element electrical is located.) But it could be from almost anywhere, so time to pull the tank.

I removed the access door and frame on the port ( inboard ) side of the galley in order to maximize the space for tank removal.
The tank has 4 pipes connected, two to the front for the Hot & Cold water and two at the back for the Supply and Return of the coolant from the engine coolant pump. I had to disconnect the mid line pipe connections of the coolant pipes in order to drain some coolant into a bucket. Then I could disconnect the Coolant pipes from the back of the tank, it's virtually impossible to capture that coolant so I let it go into the bilge and pumped it out with a hand pump into an empty bottle.

Disconnecting the Hot & Cold pipes was easy but disconnecting the electrical supply not so. I had to cut one of the wires as I could not reach down to the terminal near the bottom of front of the tank.

The Tank is held in place with 4 screws into a wooden base beneath it, easy.  I had to unscrew the water pump from it's mounting in order to be able to slide the tank out. I say 'Slide' but in reality it took ten minutes to manipulate the tank into a position that it would come out of the galley structure.

I brought the tank home plus the bottles of the coolant/water mix that I pumped out of the bilge before leaving the boat at the dock.

Seaward S-700 Hot Water Heater

After dinner, with the tank at home, I removed the Stainless Steel outer housing. All of the fiberglass insulation between the housing and the tank was sopping wet. It took about 30 minutes to get the housing off then another 10 cleaning up the outside of the tank. Now the bad news! It looks like the tank has corroded near the central weld that joins the two ends of the tank. 

Of note, I found that the previous owner of the boat had the tank repaired at some point, his name and phone number were written on the tank.  Not sure when it was repaired but I decided to bite the bullet and replace the tank.

Looking online I found the identical tank ranging from $577 + tax+ shipping from several vendors, some had free shipping but slightly higher prices.

Kuma 6Gallon Hot Water Heater

I also found another brand for $414 inc Shipping & Taxes. It looks almost identical but with a couple of key differences.
The housing is Aluminum not Stainless steel, the Position of the Cold water inlet is several inches from that on the Seaward, but other than that, looks the same unit Size and all.

The new tank 'Kuma' arrives on Wednesday 12/272023. And we are heading out on the boat on 12/29/2023 for the new year's eve cruise.

So now the question is: Do I leave the tank out till after the new year and just bypass the coolant pipes and the Cold-Hot pipes so that we can run the engine and have water pressure for the weekend trip - - or Do I install the new tank as soon as it arrives - AND - what if it doesn't arrive.

Here's my plan. I'll cut the old Cold - Hot pipes out and replace them with longer pipes and then put elbows on both of them and a bypass pipe ( PEX ) between them - That way we can have water pressue and I'll remove the rubber hoses from the ends of the coolant supply and return and then put a bypass hose between them.  So if the new tank does not arrive, then I can simply fill the coolant tank on the engine, run it to burp any air out of the system and we can be on our way. If the new tank arrives on Wednesday, then I just need to remove the pass hoses and cut the cold/hot pipes to the correct length in order to connect them to the tank, then remove the coolant bypass hose, connect the pipes to the coolant supply and return to the tank, and then top up the engine coolant tank and burp the engine and we're ready to go.

It's a plan.  I'll go down on Tuesday and install the bypasses.

Meanwhile, what do I do with the old leaky tank and that nice Stainless Steel Housing????

I'll post an update in the New Year.