Re: compression IL6
In reply to your PM
#3 has always been a problem on the inlines. In 78 or so, they found that due to crank configuration, #3 was firing a touch early, so if not good gas, and timing on the mark, it will toast #3. They offset the trigger window on 3 1978 or so, and you having a what, 82?..you are ok there. Dunno much here on the newer ones though.
Run it 21 degrees anyway, and use mid grade gas.
It looked to me like it either got hot, and/or water getting in. You know water..goes everywhere ya don't want it at times. Plus ya gotta really keep up with a good impeller...change every few years on those motors.
I'm very fortunate to have an old merc guru, who does these motors blindfolded (just built me a 72 crank up 135 for my 16" Flatbottom), and he can spot stuff no one else sees as cause. But after years, ya gain experience. He does all my work (even though its mine and paid for($2000)..its still HIS baby.
You will need a good Factory manual, toss the others.
REALLY look over all surfaces and plates...MUST BE FLAT AND TRUE..any warp, gonna be trouble down the line.
Don't know where "Clams" here has been, but he also knows those motors VERY well.
If the bores are OK (I can't see that toast piston not doing some damage though), best I can say is look it over VERY close, replace whats needed. Any rough bearings..replace, any dis-colored..same.
Keep up the progress on this same thread...don't start new. Good luck!