Compression for 2000 210hp M2

[Tomfrmnh]

Lots to do on this boat. Plan on going through the whole thing. Compression on all 6 was 150 +-4. Does that seem high? The engine was warm. Ran for about 5-10 mins prior to doing check. Also, seller disclosed water leak at base of engine where it mounts to the pump. Seems to be trickling down port side when engine running and also just with hose pressure. He thought maybe the gasket between power head and pump (drive housing gasket). It's hard to see exactly where it's coming from. Been cleaning the bilge and mount area so I can get a better look. Hoping its not too serious. Any thoughts? I will try and post some pictures or video.

 

[racerxxx]

About 125-135 is average, obviously you're on the high side. Compression tests are usually done cold.

That is a typical place for a leak on a Merc. I don't think it's too terribly hard, an engine hoist or gantry will be your best friend on that job. Make sure to clean all the surfaces , replace the gasket and there are a few o-rings on the base. Just can't stress how clean the mating surfaces need to be.

 

[Tomfrmnh]

Thanks. I will do it again cold. Hoping water leak just a seal. That is the first on the list.

 

[Murph_13]

The leak could be coming from the expansion chamber...I'd rule this out before lifting the engine...the expansion chamber gasket is an easy fix...

 

[Tomfrmnh]

Thanks Murph. I'm going to try and pinpoint the leak this afternoon.

 

[henryb]

I'm not sure how much difference you will notice on compression test between hot and cold engines, certainly there will be some difference, maybe 10%? I would be interested to hear your findings on a cold test.

Last year, I had a compression test done on the very same engine that you have, I asked Dr Honda what ranges are good and what is bad... he indicated that 140-150 is literally brand new, 120-130 is good, 100-110 is marginal, below 90 is weak.

 

[Tomfrmnh]

I'm not sure how much difference you will notice on compression test between hot and cold engines, certainly there will be some difference, maybe 10%? I would be interested to hear your findings on a cold test.

Last year, I had a compression test done on the very same engine that you have, I asked Dr Honda what ranges are good and what is bad... he indicated that 140-150 is literally brand new, 120-130 is good, 100-110 is marginal, below 90 is weak.

Had a feeling gauge may have been bad. Went and got another tester and got some realistic numbers for a 16 year old engine. Ok I guess? First gauge was wishful thinking. Ha ha

Cylinder PSI
1 121
2 125
3 125
4 125
5 125
6 127

Also 99 % sure water leak is from the housing gasket in the very rear. (Spent some "quality" time in the bilge). Now I know why no one wants to work on these things. Checked the back couple of nuts and was able to get 1/4 turn on the outers and almost 3/4 on the very rear. Still leaking though. I will order up the gasket and o-rings. Lots of work ahead. Need to chase oil warning, and TKS may be suspect as well. Had to crank couple of times then I pushed the manual button and she fired right up. Also idling very high (2200 RPM). Need to read up on setting that. Any help always appreciated. Thanks for your insight so far. Great site and resource.

Tom

 

[henryb]

Cold start idle seems to be around 1500rpm. After its warm it drops to about 1000rpm. I'm not 100% sure what the factory settings call for? Might be in the Merc M2 Shop manual?


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[Tomfrmnh]

It says 1000-1100 idle in gear in the water. Maybe the cold start and no load on the trailer might be causing the high rpm. Good excuse to go play at the boat ramp.

 

[henryb]

Yes, I read up on the Enrichment Control valve and all what it does for cold start... I think it contributes to a bit higher idle speed when engine is cold, it provides extra gas to the carbs for start up, it advances the timing until engine temp is above 122F. So I think what I was saying... 1500rpm when cold, then around 1000rpm when warm... Sounds about right.


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[henryb]

Sorry I didn't notice you mentioned your high idle speed was "out of the water".... so yes, 2200 rpm is about normal for that... basically the impeller has no resistance running without pushing any water!

 

[Tomfrmnh]

Thanks I actually reduced it to that. Guess I should take it to the ramp and put it in the water. Need to pull the engine for the pump housing gasket first so will have to go over linkage and idle setting anyway.