Water Pooled Around #1 Spark Plug

[Racer_X]

Hi, new to boating and to iBoats. I bought my first boat at the beginning of August this year, a 1984 Cheetah with an I4 Mercruiser and Alpha Gen 1 stern drive. She was well taken care of and runs great. We've been out every weekend since, sometimes twice, never an issue..... Two weeks ago, the last time we had it out the engine was bogging past three quarter when pushed to full throttle. If I back off to three quarter it ran fine and if I slowly went to full throttle from there 50% it would hit full throttle, 50% it would bog again. While idling I pulled each plug one at a time till I found the offending cylinder...#1. I also noticed water pooled around #1 plug. Took it back to the dock, pulled it and when home. Ran it on muffs and #1 plug was bubbling water from around the threads. Sooooo, I'm figuring cracked head or cylinder....do you guys concur? and if so what do you think caused it and what can be done to prevent it in the future? All life signs where were they were supposed to be when on the water since I bought it, oil pressure 30 - 40, temp never over 145, rpm and speed tracked properly based on my prop (except when the bogging stated).

Thank you for your time and advice

 

[Rick Stephens]

Time to do a compression check - do that with the engine warm, then pull plugs and spin the motor enough to push out any water in that cylinder. Once clear of water, then hook up compression gauge. Cycle the engine 5 compression turns before writing down your readings for each cylinder.

Next, pressure test the block. Disconnect and cap the water hose going to the manifold, cap the in water line port at the thermostat that comes from the transom and do a pressure test of the block cooling system..

 

[Racer_X]

Time to do a compression check - do that with the engine warm, then pull plugs and spin the motor enough to push out any water in that cylinder. Once clear of water, then hook up compression gauge. Cycle the engine 5 compression turns before writing down your readings for each cylinder.

Next, pressure test the block. Disconnect and cap the water hose going to the manifold, cap the in water line port at the thermostat that comes from the transom and do a pressure test of the block cooling system..

Ok, Thank You. I will do a comp test and pressure test. I forgot to add in my original post that I pulled the plugs after running on muffs and stuck a bore cam in each cylinder. 2, 3 and 4 looked "normal" and #1 was nice and clean as in steam cleaned...lol but it was too hard to see if there were any cracks. There was not any standing water in #1, just what I observed around the plug when on the water. I'm assuming cause I ran long enough for it to build up there.