90 Merc No Compression on #2

[hsi111]

I have a 2000 Mercury 90hp 2 Stroke that has 0 psi on #2. 1 and 3 cylinders each have 118 psi. I tried to look in the spark plug hole...all I can see is part of piston and it looks ok. No shavings found. What are possible causes. Is there anything to check without pulling power head? Ref: model 90elpto, serial 0T072541. Thanks, Rick

 

[Ebrooker007]

Re: 90 Merc No Compression on #2

You can get a better look at the condition of the cylinder walls and position if you take the exhaust cover off the side of the engine.

 

[hsi111]

Re: 90 Merc No Compression on #2

Thanks, I'll do that. Wasn't sure if I could see anything in there.

 

[hsi111]

Re: 90 Merc No Compression on #2

ok, I pulled exhaust cover real quick and the piston was sitting right where it needed to be. It's not pretty. Rings are smashed together and piston is a little melted. I just hope this thing can be rebuilt. Thanks for your input.

 

[Toddboat]

Re: 90 Merc No Compression on #2

If there's no major damage to the cylinder walls, you can rebuild it yourself. Just buy a new piston and rings and get a cylinder honing tool (google "ball hone" for images). It's a bit that goes on your power drill. You move it in and out of the cylinder while it's spinning to make the 45 degree score marks in the cylinder. It's a big job, but it's a fun project. Take a lot of pictures as you take the motor apart so you know how to put it all back together.

 

[hsi111]

Re: 90 Merc No Compression on #2

Does anyone know of a link to a service manual for this engine or have one that they can send me. Thanks, Rick

 

[emckelvy]

Re: 90 Merc No Compression on #2

Does anyone know of a link to a service manual for this engine or have one that they can send me. Thanks, Rick

This might help: Boatinfo - 1990-2000 Mercury Service manual

G'luck with the repairs..........ed