Sunday, January 7, 2018

Alternate Drive

The Wrong Drive Belt

We missed the 2017-2018 New years Eve Cruise due to a squeal from our Alternator (Here's the article about that) Short version was that we were towed from the Lake Boca Anchorage back to our Dock in Fort Lauderdale.

This post will hopefully be helpful for others that have little experience with Boat Diesel Engines, like us, even though we are climbing up that learning curve rapidly.

Background to the problem.

Over the past few months we have noticed a few odities when the engine on Eximius is running, here's some of them:

  • Engine hunting - RPM change briefly
  • Alternator shutting down - charge rate drops to zero
  • Digital Alternator charging indicator shows charging rate changing rapidly, varying by as much as 30Amps.
And the most recent:
  • Horrendous Squeal from the Alternator
  • Alternator Drive pulley too hot to handle.
The earlier issues were leading me to suspect the Alternator Regulator. When we purchased Eximius, it had two Regulators mounted in the Aft berth (very close to the engine) Both were by the same manufacturer and until I installed a new Alternator last May (2017) I thought that the smaller of the two Regulators was not connected. During the Alternator install, I found from tracing the wiring, that the Smaller regulator was in fact the one connected to the Alternator. The other is connected to the Digital Battery monitor at the Nav Station, but not to the Alternator. After some research, I discovered that the 2nd Regulator was actually a Stand by in case the main failed, however the Main was never attached to the Alternator so the system has been running off the Standby Alternator since we have owned the boat. Confused yet - think how I had been.

The Main Regulator is the one on the left. It's connected to the Digital Battery Monitor at the Nav Station but not connected to the Alternator


The 'Stand By' Regulator is the one on the right, it's not connected to the Digital Battery Monitor but is connected to the Alternator.

My guess is that when the system was installed, the installer connected the Stand By Regulator to test it (no point in having a spare if it does not work) but never completed the job and switch over to the Main Regulator.

We're hauling out the boat next week and I had planned to re-wire the Alternator to the Main Regulator and thus determine if the Stand By Regulator was causing those first few issues.

The more recent issues (Squeal from alternator and hot drive pulley) demanded sooner action, I certainly did not want to have an Alternator problem when we are motoring to the Boat Yard trying to keep on a schedule.

Getting the Alternator Tested

The day after we were towed back to the dock, we returned to the boat to pull the Alternator so that we could get it tested. I still had the old Balmar 75Amp Alternator sitting in my Garage, so I took both of them down to Lauderdale Battery & Electric to get them tested. In the meantime, I contacted 
Compass Marine, that's where I purchased the CMI 100Amp alternator and they were very confident that the bearings would be fine.

This video shows the testing of the CMI 100Amp Alternator. Greg, the tech, wound the load up and the Alternator pumped out 140Amps and as quiet as a mouse! Absolutely no squeal. I asked Greg if he would inspect the Belt for damage, as I pulled the Belt out of my bag and he immediately commented that 'That's the Wrong Belt!' 

When we purchased Eximius, I started to put together spares to carry on the boat, including spare Fuel Filters, Oil Filters, Air Filters, Zinc, and Alternator Belts - I took the info off of the original Belt and purchased two spares, yes, they were on the boat when we had the squeal, but I honestly thought that it was the bearings as the squeal was sooooo loud! But now I found that the belt was not the right size for the Alternator - It had a 1/2" Pulley and the Crankshaft & Coolant Pump pulleys are 13/32"

Ok, it looks like the culprit is the Drive Belt.

As I had the old Balmar Alternator with me, I had Greg test that too, plan is to carry it as a spare and I suspected that the bearings were going on that Alternator (that's why I changed it out last May)


This Video shows the Balmar 75Amp Alternator being tested. It's not so apparent in the video, but on-site it was obvious that the bearings were squealing. Greg commented that the bearings needed replacement and that the stator might also need replacement. That should be ready for pickup on Monday, we'll carry that unit as a spare.

Back at the boat, I re-installed the Alternator but could not get the belt tension right. Everyone that I have asked has indicated that the tension should be set so that the belt could only move 1/2" on it's longest leg (that's between the Alternator and the Crankshaft pulleys)

The problem was the Bolt that secures the upper end of the Alternator Support Arm, and the spring/lock washer that was between the bolt head and the Support Arm. The lock washer had deformed and damaged the bolt head. I decided to replace the bolt, washer and add a fender washer that could be bent over the side of the support arm to lock it in place. Guys from the C34 forum suggested that I use a longer bolt and nylock nut on the back of the bolt to secure it in place and prevent loosening with vibration.


The damaged bolt is shown above the new (but same length) bolt. I'll replace the new one with a longer bolt and and Nylock nut next week.

The Fender washer will be between the spring washer and the Alternator Support Arm, that should prevent vibration from loosening the bolt and thus

After installing the new Bolt, Spring Washer and Fender Washer, I was able to tension the belt sufficient to stop the Squeal, but the belt is still under tensioned! So time to buy/make a belt tensioner.

So, to recap:

  • Charging rates change rapidly (Alternator output constantly changes)
  • Engine Hunts (Alternator load changes)
  • Squeals emit from front of alternator
It could be the drive shaft tension!