Sport Jet 90 rebuild

[Redbarron%%]

SO with a strange noise emanating from the top of my 90 hp sport jet at idle I worried that there might be a bearing goind bad.
So I had bought a donor jet boat for a couple of hundred dollars for the rebuildable engine and the jet parts that fit from the 93 to the 95 on the Hobie Jet Skiff I have.
Well the bad news is that the crank on the 93 is a 15 spline and the 95 is a 13 spline.
So an answer was to tear the engines down for a rebuild.
I wanted to use the 93 block because of stripped threads etc in the 95 block and the ravages of salt water.
Well to make a long story ( you thought I was going to shorten it didn't you?) when I got the 93 apart (it looked really, really good on first inspections) I found that the builder left one circlip out of the #1 piston and scored the cylinder back in the cylinder where it did not show with the pistons still installed.
Well the question is the compression test ( yes I know) with my harbor freight tester was 110, 120 120 and the 93 book says that #1 is usually 10 psi lower.
SO reinstall the old pistons and ignore the problem or bore the cylinders (now 0.020) and see if a 0..040 will clean up the mess?
Who votes for which?

 

[jerryjerry05]

Bore out as little as possible.
Once you get to .040 you start getting into re-jetting the carbs.
Your motor will run with the low comp on the bottom cyl.



I had the same problem 2 weeks ago on a 89/85 the bottom piston,
the wristpin let loose and dug a BIG hole.

 

[Redbarron%%]

Jerry the scoring and lower compression is on the top cylinder, if that makes any difference.
The old motor had problems with the water jacket threads pulled out.
They had been replaced with Helicoils that corroded out the aluminum and then the insert did not work.
I replaced them with some inserts that were solid.
I could just clean everything up, hone the cylinders lightly and reuse the pistons and replace the to bearing and spend the least money.
The noise I heard was like a cage rattling in the top of the engine.
I was afraid that the engine might damage the crank and sport jet cranks are hard to come by.
Too bad the 93 had the 15 spline crank, but if I had not torn it down I wouldn't know about the piston pin getting into the bore of the top cylinder of that block.

 

[Redbarron%%]

Here is what I think was causing the noise in the top of my 90 HP sport jet engine.
I found that the top ball bearing was noisy, but that is not the big problem.
The big problem is that the bearing has spun in the block.
The seating surface is shiny and there is wear (a small amount but there) and there is evidence in the top seal housing that the bearing has turned as well.
I believe that the bearing was not well mounted with red Locktite bearing lock.
The other engine has some evidence of having turned as well with some shining of the fit area.
When I cleaned the bearings (still on the crank) you can feel the "noise" in both.
Even when cleaned thoroughly and lubed with light oil the bearings are still rough feeling.
Anyone else with some experience with the top bearing fit?