Yanmar Underwater

Hi,

I have a Yanmar 2GM20F.

My boat has sunk last year and staid in the water for 5 days. I was able to remove the water in the cylinder (only one cylinder was affected) and the moter is working correctly. I have changed the oil few times to clean eveything.

This year, the motor is still working good, but I realized that when the motor is cold, he is starting only on one cylinder. The second cylinder needs about 30 secondes to start. When the motor is hot I don't see any difference and the motor reachs 3,600 RPM without any lack of power.

What can be the problem and how can I fix it? It maybe a compression problem because one cylinder is affected? maybe the rings are jam? maybe the valve are affected?

Before opening the motor, I will like to have an idea. What should be the first steps? cleaning the injectors?

In a month I will pull out the boat for the winter. Maybe I should add something directly in the cylinder chamber for the winter time to help the rings?

If someone has an idea please let me know,

Bernard

I would pull the injectors and do a compression test to see if that shows a stuck ring, valve or something similar. If you have low compression you need to start pulling the engine down to fix it. If the compressions are both good however you may just have an injector or injector pump problem. In that case you can start diagnosing the fuel system without stripping the engine too far. If it is fuel, the first thing would probably be to get the injectors serviced. Is the engine extra smoky at start up?

Thank you Aliboy, I will try to make a compression test first and I will have a better idea. I will let you know. The motor is making a black/brown color smoke at start when cold. No smoke after.

Dear Aliboy,

Where can I buy a compression tester that will fit for my Yanmar?
I can order it by Fedex, I have an adresse up North New York state.


BMc

Sorry BMc I don't live in the US so can't advise. I guess your compressions will be in the range of ~400psi (only a guess though), so you need a gauge that will read a bit more than this. Most diesel testers seem to read up to 1000psi so any of those should be fine. Note that if you have glow plugs in that engine you can also test the compresssions through the glow plug hole and many testers will come with standard adapters for this. Usually easier than pulling the injectors as a first check. Sorry I can't help more re the tester, but there are a bunch on eBay that you could check out.