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Yamaha 15sk stuck

S

supersix

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Hello.I just picked up a 15 h

Hello.I just picked up a 15 hp Yamaha sk motor.I believe it's a 1985(?).My problem is this motor will not pull through.I tried to shoot some oil in the cylinders to free it up but so far no luck.Wanted to know if you all think that this motor is blown.Thanks.
 
remove flywheel cover and use

remove flywheel cover and use a socket wrench on the big flywheel nut...spray some Seafoam Deep Creep into spark plug hole and leave it overnight and it may loosen stuck piston/rings.
Good luck!
 
The motor is seized up due to

The motor is seized up due to water getting inside...even if you free it up the rings will be stuck in the pistons i would strip it down and access if it is any good to rebuild
 
"It could well be seized up, b

"It could well be seized up, but maybe worth a try to get it to turn over. Hopefully the lower end/crank/bearings and all aren't rusted together..."
 
Thanks for the advice.I tried

Thanks for the advice.I tried to free it up by putting a socket on the flywheel nut but it won't budge.Is there a chance something is holding the flywheel in place?Thanks.
 
"next remove the spark plug an

"next remove the spark plug and if possible insert a wooden dowel pin or plastic rod into the spark plug hole to contact the top of the piston and tap on it with a hammer, which could knock it loose. The Seafoam and the tapping might make it move. Good luck!"
 
I pulled the motor out of the

I pulled the motor out of the housing and pulled the head off.It's a little rusty but not too bad.I soaked the cylinders with penetrating oil and put a rag on top of the pistons and tapped them with a wooden dowel and a hammer to try and loosen it up.Still won't move.Maybe it's the crank and rods?
 
"could be the crank/rods/beari

"could be the crank/rods/bearings, but keep trying on those piston crowns, probably the rings rusted to cylinder walls...maybe a bit of heat on the piston crowns with a propane torch? heat might help but be careful. how long since this motor was run? maybe they just laid it up wet and everything rusted together..."
 
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