scratched crankshaft?

[hibridge]

hi all,
not a mechanic but I am a fisherman. I live in mexico and have a 1989 force 90 hp. I am on my second rebuild and not too happy about it. I went to the states and came back after two months and the mnotor would not start. mechanic said it was probably a stuck ring.he took the motor apart and sure enough the rings were stuck on two of the pistons. he says he can free the rings and reset them but also says that the bearings are starting to pit or scratch the crankshaft and motyor will probably not last too much longer.I can see a little etching on the crank but do not know what would be normal?looking for some advice if anyone out there can give me some.

keep in mind we have a language barrier of sorts, and also it's mexico. don't know why the rings got stuck. over the last 8 montyhs had about 30 trips and 160 hours. when i left it all ran good.

thanks
jim

 

[jerryjerry05]

Re: scratched crankshaft?

The rings stick because of cheap oil,older oils(TCW/2 or older).
Carbs out of sinc or a lot of ideling.
Minor scratches can be honed out at a good machine shop.
After I started using TCW/3 I didn't have to rebuild my motors again.I had a pair of 88/85hp and had probably 600-800 hours when I removed them and replaced with a bigger motor.
Make sure the carbs are set.J

 

[hibridge]

Re: scratched crankshaft?

talked to friend here in mexico and he said why not turn or machine the crankshaft. my mechanic said he cannot get the different size bearings I would then need. I am anot talking about the main bearings but the bearings behind the rods. can i buy different sized bearings so i can have the crankshaft machined? are they avaialble?
thanks
jim

 

[jerryjerry05]

Re: scratched crankshaft?

Try Florida Marina@ Boat sales.(410) 255-4365 The parts guy is really knowledgable on parts.
Ask for Bob in parts he can tell you what's available.Look on e-Bay or ask on this site for used parts.
Post some pics of the scratches.So we can see how bad it really is.J

 

[Frank Acampora]

Re: scratched crankshaft?

1. You can NOT turn the bearing surfaces. They are hardened to greater than 64 brinnell and must be precision centerless ground and polished. The average machine shop can not do this.
Oversized rollers are not available.

2. No amount of etching, pitting, scratching, or corrosion is acceptable with the exception of almost non measurable marks that can be polished out.
The engine will run with some etching, corrosion, or pitting marks but the service life will be reduced.

3. Polishing too much off the diameter of the crankpins will cause the rollers to skid and squeal under acceleration, reducing the service life of the engine.

4. If the crankpins are etched, it is almost a certainty that the rod big ends are also. This requires replacement of the rods.

You need to face up to it: Eventually, probably soon, you will need a new crank and rods or engine short block.

I did use a crankshaft with minor etching of the bottom crankpin once as an experiment. The engine ran for one season and then--- I can't tell you how many cranks I have discarded for etched crankpins. This is one condition that is almost certain to cause the engine to self destruct. Usually at the MOST inopportune time.

 

[nymack66]

Re: scratched crankshaft?

Call this company they will help you ..Ask for Dave ..
Marine Crankshaft 1 714 549 2388
2155 So. Grand Ave
Santa Ana , Ca 92705

 

[robert graham]

Re: scratched crankshaft?

Maybe try to find a good used motor same as yours, then use your motor for parts in the future. Bet your crankshaft and other internal motor parts has corrosion from salt water usage, after 20 years it may be time for newer motor? Good Luck!