A dirty after cooler???

[Raymond Slingerland]

Boat with the 300 hp 6btas. Going to wide open throttle port moves up to 2700 max and the starboard lags behind it and only reaches about 2600. Clean bottom, but boat not used much over the last year. What comes to mind are over propped, reduced fuel supply from dirty filters, or as the man demonstrating the boat suggests, starboard engine after cooler needs cleaning. The man is in business as a diesel mechanic and has taken care of the boat for the owner. He rules out the props since he has seen better performance in the past. Filters not likely, not many hours on them, but what he sees suggests the after cooler. The starboard engine lags behind the port engine coming up to rpm and eventually tops out 100 to 150 rpm below. This performance is holding down the port engine such that it can’t reach a higher rpm. Also on the starboard engine block there is a light oil film maybe from a head gasket leak. Don’t know if two are connected but would like to start with the mechanic’s theory, clean the after cooler. What do you think?? Thanks

Topic

[Tony Athens]

Don’t procrastinate? DO IT!
It’s all here :

Cummins Marine Aftercooler Maintenance

Tony

[Raymond Slingerland]

The after cooler

Good to know that it is serviceable. Thanks

[Tony Athens]

You have an up-graded aftercooler that was designed to be serviceable.

Tony

[Raymond Slingerland]

after cooler?

Here are a couple from the survey. I admit I don’t know what the aftercooler looks like on the Cummins. The drawing posted earlier didn’t print out for me.
These are jpg so not the best but??? If they aren’t the serviceable after coolers than the owner’s mechanic is misleading us, since he indicates he has serviced them in the past and told us how to do it—but maybe that was all on an engine that could be serviced. If they haven’t been upgraded give me a ball park dollar number to do that? Thanks

[Raymond Slingerland]

aftercooler pic

Can you tell from this picture if after cooler has been upgraded?

[Rob Schepis]

See attached —- Per your SN you do have the welded aftercoolers …. Maybe they have since been upgraded to the serviceable aftercoolers? No pics available?

[Raymond Slingerland]

engine numbers

CPL 0970, SN 44547345.
Understand they are early 90s engines. Some had non serviceable after coolers I am told. But since the mechanic indicated he had service them before I assume either these have been changed or were not the non servicable ones.

[Raymond Slingerland]

additional low power comment

Great article that was referenced. Owner is going to have his mechanic check it out. His mechanic thinks it is dirty aftercooler since he has worked the boat before and knows the existing configuration can do better.

Reference the props–Since props move the boat I would like to have the best prop fit, and I understand the biggest diameter should come first and than pitch to make the desired rpms. If that is correct, the tips on the existing 3 bladed props on the boat are at least 4 inches from the hull. It is my understanding that could probably go up to within two inches of the hull. At haulout could not see any numbers on the props, so probably covered by the nut on the end. Owner doesn’t know prop size or pitch, just that they have worked for years.

[Tony Athens]

Post a serial number as there are various 6BTA 300’s.

Tony

[Raymond Slingerland]

smoke?

Very little, some what grey. Not steam.

[Rob Schepis]

You don’t mention “smoke” or “no smoke”. Sure it “could” be a fouled aftercooler but, until each and every item is verified, it could be several other issues as all described here: https://www.sbmar.com/articles/understanding-low-power-troubleshooting/

[Author]

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