6BTA Funky Electrical Issue (voltage and temp)

[wisekrakencharters]

In need of some opinions, where to go next…

I run a 38′ Evans with twin Cummins 5.9 6BTA Diamond Series 370hp. 2200 hours

WOT 3000 rpm I usually cruise at 2200

I’ve been chasing an electrical issue for the better part of a year. Frirst, temp would show to climb(not every trip and usually just part of a day), and on occasion, high temp alarm would sound. With a temp gun, we could confirm that the engine was in fact running at its normal temp( for my boat they run 188-191) and pumping good water. After some time we noticed that it seemed to coincide with a voltage drop on the main pannel.
This engine in particular, uses an isolater to charge up the 12v house battery. First thing in the morning it would read 13.1 – 13.3 while my house batteries would get around 14.2. Sometimes, as the day goes on, the voltage on the panel will drop to 12.5 – 12.8 which seems to cause my temp gauge to creep up?

First thing i did was pull the harness connections at the helm and engine itself to clean. Engine side was visually, slightly dirtier. Wire brush, sandpaper, and back together with dielectric grease. Made a difference for a couple weeks, then back to acting up. Back and forth for a while un-pluging, cleaning and back together. Hard to say when it helped since the issue was somewhat inconsistent anyways.

Next, i swapped the alarm circuit board(was suggested by someone with a simmilar issue in my area). immediately after, the voltage on the panel read the highest i had seen it. 13.5 or so. But, that only lasted a few trips then back to acting up.

Next, it was suggested i bypass the extension harness. I cut the hot wire, and spliced in a direct run up to the key switch on Panel. Again for a time looked great but after few trips the voltage would creep down and temp would go up.

Replaced the 8D Batteries, new islolater, no change

Tried a new alternator( 145A from here). 2 weeks were great, then back to its old self (with the new 145 Amp, innitial voltage would be higher than with the original 105 Amp. But would eventually creep to 13 or 12.8)

Doubled up on the house 12 v

Back to a re manufactured Delco Remy 105A

Every change i made helped for a short period of time. Its driving me insane…
Should i purchase a new on-engine harness? $500 just to troubleshoot?
What have i missed?

Thanks
Matt

Topic

[Rob Schepis]

Matt,
Further to Tony’s recommendation, I would setup DVM’s to each bank and post a wiring diagram of your setup.
https://www.sbmar.com/articles/installing-digital-volt-meters-dvm-boat/%5B/url

John,
Sounds like an issue at your “engine mounted circuit breaker” that feeds your helm….. do some searching on this forum for those terms with me as author. Again, DVM’s would be key here as to diagnosis..

1 user thanked author for this post.

Tony Athens

[John Muldoon]

I have the same engines in a Silverton and unfortunately have experienced similar issues. one of my engines has a steady voltage reading of 14 – 14+. The other engine just started bouncing from 12.8 to 13+ and eventually falling as low as 10.5. I replaced the original alternator with a 145 amp and also replaced the batteries for that engine. nothing has actually fixed the issue and the issue comes and goes. I’ve checked the volt reading at the alternator and at the key and both show 14+…the other odd thing is that this engine also shows low oil pressure on the trouble side…half of what the other engine oil pressure gauge reads. Temp gauge is consistent on both engines.

I too was told it must be in the harness at one of the connectors.

I hope someone actually comes up with the answer for both our issues.

[Tony Athens]

What have you missed?

Simple——————-you are not measuring battery terminal voltage.. You are measuring panel voltage thru many different systems, wires, hook ups, etc, ..

Until you do that, it’s impossible to troubleshoot of find where the issue is..

Look it up as to “how too”..–Plenty of stuff on this web site and forums on the subject.

Tony

[Author]

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