70s model mec. 50hp need advice before i junk it

its a 2stroke, we haven't had the motor very long, and we aren't quite ready to spend the money on a new motor, but here is the whole story.

Our first day out on it, the motor ran great, suprising power, and ran very smooth, just as we were about to head back in, it just lost power and shut off at WOT as we were turning. we got the boat home and changed the plugs and it ran. then my dad was rev'n the motor in the yard with muffs on it. now the motor spits oil/water mix out of the bottom carb. also the cyl#3 sprays water out of it. and will not run if we put a plug in the third cyl. i don't think the head is cracked and he didn't over rev it in the yard. i was wondering what other senerios could cause our problems. BTW the motor runs great on 3cyls just no power, and the fact it sounds like tractor and spays water inside the cover.

btw could the reed valve being messed up cause this problem.
also we changed the gasket, and gastkets on the left side looking at the rear of the motor.

thanks for your help in advance.
josh

Re: 70s model mec. 50hp need advice before i junk it

Welcome to iboats!

Get a compression check on all cylinders. Should be over 100 and all within 10% of each other. NEVER rev on muffs.

Re: 70s model mec. 50hp need advice before i junk it

cyl#1[120psi], cyl#2[120psi], cyl#3[15psi], cyl#4[110psi]

what could be wrong with it, from my understanding 2strokes don't have valves...so the head must be cracked right?

is the motor junk?

Re: 70s model mec. 50hp need advice before i junk it

help?

Re: 70s model mec. 50hp need advice before i junk it

Did I read that correctly or is it a typo regarding 15 psi on cyl#3? If it should read 115 psi then compression doesnt seem to be a problem. If the motor is anything like the inline 6 motors, you may have a hole in the exhaust plate allowing water into the cylinder. I dont speak from experience, just from the limited knowlege that I have gained from visiting this forum.

Re: 70s model mec. 50hp need advice before i junk it

no i tore the front of the motor apart, took the carbs of..etc.. well the lower carb i can see in there that the reed valve is broke, or something, so i'm gonna take the power head off and replace the reed valves. and it was 15psi.
i looked inside the spark plug holes and noticed that #3 was dry. so i put some oil in the hole and spun the motor a little with my hand, rechecked the compression and waallaaa 120 across the board.

but yes the reed valve is fuq'ed so i'm gonna replace it and the exaust plate and gasket and see if that fixes it.
btw i looked at the top of the pistons though the holes, and no scaring or holes so maybe running the motor with the #3 plug out spit the peice of the reed valve out . pistons look good. i'll keep yall posted...any key things i need to know when taking the powerhead off?

-josh