1984 90HP Johnson piston scuff from water

[karrick]

J90TLCRD SN 5990307

Picked up motor for a steal last night knowing 2 cyls had water damage from leaking exhaust cover gasket. According to previous owner Motor still runs fine but has trouble running at low engine speed. but once up to speed still runs like a top. He had local mechanic check the small water leaking into cowling and had good compression (don't know exact #s) but advised a good hone job and new piston kits after seeing the damage behind the exhaust cover. Do I need to go to bare block to hone/repiston?? Just wondering if anyone has experienced this issue before..

 

[wbblc87]

Re: 1984 90HP Johnson piston scuff from water

J90TLCRD SN 5990307

Picked up motor for a steal last night knowing 2 cyls had water damage from leaking exhaust cover gasket. According to previous owner Motor still runs fine but has trouble running at low engine speed. but once up to speed still runs like a top. He had local mechanic check the small water leaking into cowling and had good compression (don't know exact #s) but advised a good hone job and new piston kits after seeing the damage behind the exhaust cover. Do I need to go to bare block to hone/repiston?? Just wondering if anyone has experienced this issue before..

In my experience, you will most likely have to replace all 4 pistons and bore the block oversize. Disassemble it and mic the block. Pay special attention to the cylinders around the exhaust ports. I normally find about .006-.008" of warpage, wear and out of roundness in this area. If you find anything over .004" that cylinder needs bored. If you don't bore it, it won't ever idle right.

 

[Dhadley]

Re: 1984 90HP Johnson piston scuff from water

Yep, besides -- if you're going to buy new pistons anyway it'd be silly NOT to bore it.........