1987 Tohatsu 9.9 grinding engine noise

[Wayne Burgess]

My 9.9 has had a scrubbing/grinding type noise when running and does not like to idle slow, seems to be in a bind. Local backyard boat mechanic seems to think the motor is spinning a main bearing and would not be worth the expense to repair. I have a second 9.9 same model but it only has 75 psi on each cylinder,he says it wouldn't be worth the expense to swap power heads with that low of compression. I have never disassembled a boat motor but have mechanical experience repairing automobiles. What is the best way to make one good motor out of this or should I part them out and buy another motor?
Your thoughts appreciated.
Wayne

 

[Sea Rider]

Re: 1987 Tohatsu 9.9 grinding engine noise

If you change top bearing better change bottom too assuming all other crankcase parts like middle bearing, crank pin, needle bearings, etc are still in good shape, could take advantage and change new piston rings too. If the second engine low on compresion only needs new rings or probably 0.5 mm piston and rings and other parts are ok go for the less time demanding work, definitely hand labor will be cheaper, but that depends on how much your mechanic wants to charge you... Or pass the used bearings of the low compression engine to the noisy engine if don't plan buying new parts.

Happy Boating

 

[pvanv]

Re: 1987 Tohatsu 9.9 grinding engine noise

Since it appears that you have 2 bad motors right now, no harm in doing a more thorough diagnosis. Don't guess about the bearings, check them. What actual models (not years) are your motors? Beware the older, obsolete models for which carb bits are NLA.

 

[Sea Rider]

Re: 1987 Tohatsu 9.9 grinding engine noise

Bearings usually last very long on these motors, that is if correctly lubricated, other parts to check are small black hoses that sends proper lubrication to upper and lower main bearings, sometimes cracked hoses or obstructed/inoperative interal small hose check valves located at extremes will give you bad bearings failures.

For your backyard mechanic to say that because "probably" main bearing is spinning would not be worth the expense to repair that engine is a very light and killing statement, parts are relative cheap, Tear crankcase block appart and check bearings and general rotating parts for a true on spot diagnosis.

Happy Boating

 

[robert graham]

Re: 1987 Tohatsu 9.9 grinding engine noise

MAYBE a nut, bolt or fastener has vibrated loose under your flywheel and is stuck to the magnets causing that scrubbing/grinding noise?... maybe pull the flywheel to check. It would be sweet if that's all it was!

 

[pvanv]

Re: 1987 Tohatsu 9.9 grinding engine noise

MAYBE a nut, bolt or fastener has vibrated loose under your flywheel and is stuck to the magnets causing that scrubbing/grinding noise?... maybe pull the flywheel to check. It would be sweet if that's all it was!

YES !

Don't guess, Diagnose.

 

[Wayne Burgess]

Re: 1987 Tohatsu 9.9 grinding engine noise

Thanks for the feedback, I guess if its broke I can't hurt it by tearing the motor down, it will be a learning experience as I've never been into a boat motor.I have come across a 1996 9.9/15hp power head so now I need to ask two more questions: Will it interchange with my 1987 9.9? Can I purchase a manuel that give step by step instructions on rebuilding and repairing these motors.

 

[pvanv]

Re: 1987 Tohatsu 9.9 grinding engine noise

Year of manufacture means nothing for servicing a Tohatsu. Model/serial is the defining point. Yes, the Factory manual is available from any dealer, including me.