Mercruiser 3.0/Alpha 1 drive Compression issues.

[Chemdawg]

Hello everyone. I have a 1987 Arrow Glass Carisma 185 with the mercruiser 3.0/Alpha 1 combo. Engine #B523519. After dealing with my fuel and spark issues, and rebuilding the lower water pump/impeller assembly, I finally got everything running using my rabbit ears. Motor ran great. Took it out to the lake, and it ran well at about 40 mph/4500 RPM. Today I went to check the oil, and noticed the light solid tan color. Kinda milky. Oil isn't over full, so I know if it's some water in there, it's DEFINATELY not pumping it in big time. Pulled each plug out one at a time, and checked compression. On the plug side going from front to rear of motor:

1: 110
2: 80
3: 80
4: 110

Now i'm no boat expert, and am very new to this, but with my experience with car engines, and hotrods, that tells me that I have a blown head gasket.

I'm not for certain... Just my observation. Now I don't have the equipment to do a leak down test to each cylinder, so I did not try that.

In the beginning, once I got the fuel/spark issues handled, and got it running, I noticed it was over heating. Didn't let it run but for a few seconds once it got hot. I replaced all the impeller parts, and upper tube portion of the impeller. I also replaced the stuck open thermostat. After that, there was NO over heating. Ran very well.

Does this sound like a head gasket?

 

[alldodge]

Re: Mercruiser 3.0/Alpha 1 drive Compression issues.

It was doing fine until the over heat, after the impeller was replaced no over heat but now water in the oil and low compression on two cylinders. Yep looks like head gasket to me

 

[stonyloam]

Re: Mercruiser 3.0/Alpha 1 drive Compression issues.

It could be coincidence, but it kind of Looks like it might be blown between 2 and 3. This has worked to diagnose: Take off the valve cover, pull the plugs, turn the engine until you see both #2 valves close, put compressed air into #2 plug hole and see if it comes out of #3.

 

[Chemdawg]

Re: Mercruiser 3.0/Alpha 1 drive Compression issues.

When I bought the boat there was no water in the oil. First time I ran it and it overheated, there was no water in there. After installing the impeller kit, and getting the water flowing, didn't appear to have any water in there.

Took it out for about 40 minutes on the lake, and that's when the water was apparent. Checked compression, and those are the numbers I got. I am about 90 percent positive that it's a blown head gasket. However I've been put in my place numerous times with my assumptions on this forum. Alot more experience out there than me.