Replace piston, or just the rings?

[Teddy78758]

Hi, need some advice. I'm in the process of rebuilding my 1991 Force 90hp and finally got the powerhead down to the pistons. #1 and #2 look good (I think), but #3 looks a little iffy (both piston and cylinder wall) and I would like to hear your thoughts on whether to repair (new rings and cleaning) or replace (and possibly bore the cylinder). I am an advocate of doing things the right way the first time, but don't want to spend more money than I need to. I have included pics of both sides of the piston, as well as the corresponding cylinder. On both the piston and the cylinder, I could not feel any scoring to speak of, and there were no other obvious signs of wear.

Thanks in advance!

 

[Faztbullet]

Bore all three .020 reassemble and enjoy boating....

 

[jerryjerry05]

No need to do all 3 cyl.
If there is NO wear on the sides of the other pistons and cyl. walls????
Then reuse the old.
Lots of motors running with one piston different in size.

The cyl. will need a bore job.
Take it to a machine shop and they'll tell you how much they can remove.
The .020 should be enough but not being able to check it myself??
I would be guessing.

Try to figure out why that cyl. went bad??
Recirc system clogged? sucking air somewhere? carbs not sync'd? running hot? clogged cooling passages?

Replacing the piston: The OEM needs a special tool to install the wristpin and bearings.
I use Wiseco and you need the wristpin kit and rings to make it work.
Wiseco rings won't work on OEM pistons.

Get a factory manual for the specs on ring end gap clearance and torque specs.
Clymer/Seloc aren't good enough.

The exhaust chest: if it doesn't leak?? don't remove as it's a B to reseal and make water tight.
If you do take it off?? get the surface milled on the block and the cover.
The years of use eat away at the edges and make it hard to seal.

 

[gm280]

Good info provide already. My only suggestion is to clean everything before making any decisions. Hard to tell if any of those score marks are serious or not with everything dirty. JMHO