frankmeltzer

[frankmeltzer]

hello, I own a 1989 90hp yamaha outboard that I bought new at harless marine in coos bay oregon. my local yahama dealer just diagnosed my motor as having a dead cylinder # 3 Is this motor fixable? Thank you for your reply.

[99yam40]

what is wrong with it? dead could mean a lot of different things.

[Sparkieboat]

99 is correct. you need to get a price to fix it, if the price exceeds the value of the motor, then just get another motor.

[frankmeltzer]

Thanks for the reply, the tech just told me that there was 120lbs in 1 & 2 and zero in #3 as it is, the 40 yr.old boat is just about worthless so I might dismantle the engine just to see what happened. One yahama guy told me that california's 91 octane gas would tear up the motor. and I ran it with 91 for 10 minutes before it started acting up

[99yam40]

Yes, lost compression is something you need to open up the motor to see what has happened.
If it is a hole in a piston and no other damage to cylinder or bearings it would be an easy fix by replacing piston and cylinder honed
If melted piston and scuffed wall, as long as it is not too bad you can have the cylinder bored and piston replaced

If there is a problem with bearings and crank, you probably will not want to buy crank assembly.

What ever you find you need to find out why it happened or it will happen again.

these motors are designed to run on 87 octane, higher octane fuel burns slower and maybe it got the exhaust side to hot as it was still burning as it left the cylinder.
Or the cylinder was running too lean due to plugging in carb, causing melt of piston.
Or too much fuel in crank case of #3 due to leaking fuel pump causing walls to be washed of oil.

Any way, if you have to pay some one to fix it it may get very costly, but it never hurts to ask for an estimate

[frankmeltzer]

Thank you so much for your help.