3GM30F Service Issue

[Scott T-Bird]

With all due respect @Scott T-Bird - everything @skunther is describing about how his engine is running can easily be due to low compression. It can't be as low as his original numbers quoted or his engine wouldn't run - at least I've never heard of a diesel that could run at those compression levels.

Well, I was reading that he finally achieved 3500 rpm under load and that is where it should be. That wouldn't be a symptom of low compression. I also thought that the starting battery is overly small - until he tried one with higher capacity, but I don't really have an opinion about that based on knowledge.

Still, I agree that if there continues to be symptoms of low compression, such as excessive blow-by, discolored smoke and the odor of burning oil, by all means, check out the compression. I also agree, that the compression numbers stated (by his mechanic?) seemed to be BS given the circumstances we know about now. An inaccurately high instrument reading of rpm both before and after the work done, could be disguising a problem that needs to be addressed.

Perhaps he doesn't need to be doing a ring job right now during the heart of the season ....

 

[skunther]

I’ll note to confirm the rpms and compression at the end of the season.
FWIW, I did have the oil tested a few years ago, while it was running as it always had, prior to work performed, and it checked out fine. I assume blow by would cause some red flags on oil test results?

 

[dLj]

Well, I was reading that he finally achieved 3500 rpm under load and that is where it should be.

Oh, I missed his post where he said that the next run he was able to get 3500 rpm, I had thought he was only able to get the earlier number of 3250 rpm. He may well have gotten the rings to seat.

dj

 

[skunther]

We are into our trip, and the engine is now showing 3250rpm again under load at WOT. I’m not certain if we had a tailwind when I got 3500rpm before, but we’re not getting that now. Still some white smoke and sheen at startup. Engine room also smells of diesel when running, but I can find no leaks.

 

[MitchM]

any mechanic re using any copper washers in a yan mar is a big NO. they'll never put them in in the exact same orientation; leaks develop, engine runs poorly. the most common error is re using the copper washer in the secondary fuel filter. but like Scott T Bird (one of the previous posters on this thread ) suggested-- check whether the 'rebuild mechanic merely re used all the old copper parts. (and if s/he did --- do NOT pay for the repairs. ( OP check your invoice-- did they charge for new copper parts? order the yan parts manual for your engine and verify against parts shown on your bill. the yan service manuals clearly say DO NOT reuse certain copper parts. . . )

 

[skunther]

I will check invoice and see. at this point, we took the boat out for two straight months, and we never let it sit for more than two days. It would still start rough, but if I had the throttle at 100% it would start within 7 seconds, though with some smoke. Much rougher and much more smoke than it would before work performed. However, after letting it sit for three weeks, I started it up today and it starts almost the same - rough, but within 7 seconds at full throttle. It’s as if every time I let it sit for more than one day, it’s starting as if it had been sitting all winter.
Also, I am currently only getting 3150 RPM at WOT.

 

[skunther]

Following up on this. I earlier this spring tested how heating the air intake for 10 minutes with a hair dryer would affect the engine starting, and after doing so on a cold morning after sitting for weeks, it started up within 3 seconds.

I have heard of pre heating systems that can be installed on the Yanmar 3GM series. Does anyone have any knowledge/experience/recommendations in this regard? Is there something I can install myself?