Mercury 850 intermittent cranking issues

[oldhits]

Hello, I'm having cranking issues with my 78 mercury 850. Last week I was running it on water muffs in my yard, adjusting throttle cable and idle stop bolt, and gear shift adjustment, while shifting and revving throttle the muffs came off without me noticing, the engine started squeaking and stopped, would turn over, I pulled plugs and sprayed with wd-40 then got it to turn with ratchet on the flywheel, I did a compression check all 4 was right at 122 except no. 1 was at 112, anyhow when you crank it over it will intermittently freeze up with the squek/squeal noise at times will turn over for 10 seconds and other times only a second or two then gets tight again, then I spin it a couple times with ratchet and it will free up again, I pulled the lower unit and no change. Does anyone have an idea what would cause this, maybe a reed valve or something loose in the crank case? This is my first boat and am not familiar with 2 strokes, I am mechanicly inclined though.
Thanks for your time and opinions or experiences.

 

[hotrod53]

I hate to be the bearer of bad news, but that sounds critical. They say an outboard will overheat in a very short time. Your compression sounds good except for the fact that one is a bit different than the other 3, I don't think it's a piston but possibly a bearing which would require a complete tear down. From what I know of reed valves in 2 strokes, that's not your issue.

 

[oldhits]

Thanks hot rod for taking the time to read my post, stupid mistakes sure can be costly and time consuming, I been reading and thinking of this problem non stop for a week now, that's the conclusion I can only think of, its just weird feels like something dragging/sticking when cranking till it won't turn over, then I free it by hand and it feels fine, sometimes for several cranks and then binds up again, then I repeat over and over with same results, it can sit for a second and I can free it right up, I let it sit for a day to see if something was swollen and would cool and unfree after cooling and nope it dissent only way to free it is to use a ratchet on flywheel, it turns really hard for a complete reveloution or two, once freed up it will crank over a dozen revs and other times only a couple revaloutions before freezing up, strange. I am starting to pull the whole power head, going to get it on the bench for further inspection.

 

[oldhits]

Wanted to update my findings, I got the engine on my bench and pulled the lower hub, and the bearing is chewed up in two a couple dozen prices, the crank shaft end has a little scoring, I think and hope it is OK, no damage at number 1 cyclinder port. Looking in from the crank opening I can see two of the reed pedals are open a good 1/16 of an inch, should they be shut? Can I bend them a little? Also the inside of the hub is pretty well scored up, might need a new one.
Seems as it was already heaaded for disaster as the lower crank seal has been leaking for some time now, and adding my oops didn't help.
Looks likeI will be ordeiring some parts asI likei this engine, it ran strong when it did. Would move my 68 16ft renken across the water at 40 mph. It would often have problems taking off it would stall out, at times you could get it to go by going ffrom just getting into gear and the full wot. So she needs some carb work also.

 

[oldhits]

Just wanting to update my post, got my mother back together, I replaced the upper and lower crankshaft bearings and seal, cleaned the carbs a little, pulled the exhaust plate cleaned everything new seals, took it out today, ran great at idle, but has a problem taking off, it will bog down and stall, if you baby it a little once in gear and then wide open she will take right off, 1/2 or 3/4 throttle you get no response, then it stalls. Not sure if its a fuel problem, fuel pump/carb or the advance trigger. Once I got moving it ran strong 35 mph she's got a little more to her, but my cabbles needs replaced, so I'm not able to get full throttle.