wrecked piston

[bwilson2626]

Facing from the rear, the lower right piston is pretty shot. looks like i took a chipping hammer to it & the matching head. cylinder walls do not look visibly damaged but show little to no cross-hatching remaining.

Couple of questions -
Is rebuilding even an option? If so, could a (somewhat) decent mechanic like me, with guidance from excellent mechanics (Y'all) stand a chance at successfully completing?

Would saving up & buying a remanufactured powerhead be the smarter way to go?

Honestly, I'm leaning towards the new powerhead, because a complete rebuild is pretty intimidating. I've rebuilt a couple chevy engines before, years ago. But I've never got into one of these.

 

[racerone]

Must be a V-4 or V-6 crossflow with the classic broken piston ring syndrome.----Model # of your motor # ?------Tear it down and see what needs to be done.----Easy fix I think.

 

[F_R]

Yes, something has broken, and the engine has swallowed the pieces. Ring, or whatever, it has to be torn down to evaluate. Easy for us, don't know about you. But that's why we get paid to do it.

 

[bwilson2626]

Racerone & F_R, for sure something broke, I highly suspect the ring.
Apologies for not clarifying the key details, I know better.
Its a 1998 90hp spl. Flathead, crossflow.
Currently, the compression tests are 105, 102 (left bank) & 102 & 78 (right bank).

If I do attempt a rebuild, would I have to take the block to a machine shop (assuming there is no damage to cylinders) to have it honed or crosshatched?

 

[bwilson2626]

Model # is j90tslecm.
90° crossflow

 

[healey8390]

If you don't have deep gouges in the cylinder you could possibly get away with a ring job and the one piston in my opinion. I would recommend the rebuild on how much you are willing to invest along with how long you plan to keep the engine.

I overheated my 86' 110 (pretty much the same motor as yours), and went with rings,a used crank and two used pistons and two used rods. My original plan was new pistons and rings for all four but I had pitting on the crank and two rods, and the upper bearing. Since I don't see the boat/motor in my long term future I went with rings, a used crank, two used pistons & rods, and new upper, main and lower crank bearings. One could argue, hell pistons would have only been another $250-$350 so why short myself? If I was going to keep it long term I would have but I don't have the money to spend the extra couple hundred x bucks vs. time saving and being on the water now if that makes sense.

Long story short it runs good enough to get my by for a couple years. Compression is 105,105,105, 112. Not the greatest but that's the risk I was willing to take. If it lasts a couple years as it likely will. I saved the hassle spending the amount I invested on what I could have bought a like engine that I have no idea what's been done to it or what it needs. A win in my book....

 

[flyingscott]

Your block will have to be bored out. Look at the piston and see if there is a size or a part # on it, should tell you what size the piston is. You do not want to re ring a crossflow piston. Go with all new pistons and do it right.

 

[racerone]

Agreed----New rings on an old crossflow piston is a mistake.----These engines are so simple and run so nice when properly rebuilt.

 

[bwilson2626]

Honestly, i plan to keep this boat/motor as long as possible. If I do go for the rebuild, I would for sure go with all new components. I have seen a few complete rebuild kits online that look to be all inclusive. Do you guys have any experience with these? Recommendations?

After having the block bored, would that change the size of the new pistons, or would the new rings compensate for the added bore I.D.? Seems like custom pistons would be in order, but thats just a guess. Again, thats assuming no gouges/damage, in the cylinders..

I just bought a 94 johnson 112hp, just to keep me runnin till I can get the rebuild completed. I'm wondering if some parts will interchange, like lower unit, carbs. ect..

 

[racerone]

????----If you bore 0.020" out of a cylinder you fit new pistons for a 0.020" O/S bore.----And you fit 0.020" O / S piston rings on those pistons.----The 112 HP is the same engine as the 90 HP.----O/S pistons for these are on the shelf.----Lots of demand for them.