Tohatsu m8 2003 8hp jumps up and down

[ba_50]

The motor ran normally the time before.
This time when trying to accelerate above low speed or idle it would buck or jump up and down like the the prop was hitting bottom, yet it wasn't.
I had a different motor that needed a new hub, but this seems different.
The gear oil is good.
Spun prop or something else?

 

[MattFL]

Could be a broken gear in the lower unit.

 

[airshot]

Drain the gear oil and look for metal pieces. Make sure prop is not damaged. Are the transom clamps tight !!

 

[pvanv]

Also verify shift rod fully engaging, not just barely.

 

[ba_50]

Every motor I have used will pull through in forward or reverse but this won't do it.

 

[ba_50]

There were some fine filings in the oil.
This motor has about 20 hours on it.

 

[ba_50]

Every motor I have used will pull through in forward or reverse but this won't do it.

It will shift into forward but not reverse

 

[KJM]

There were some fine filings in the oil.
This motor has about 20 hours on

 

[KJM]

I was going to say about warranty, but then I noticed its 20 yr old! Has it worked fine up to now or is it new to you?

 

[ba_50]

No problems till now. Only 20 hours on it as far as I know. The transom board looks good. Maybe it is flexing. I put it in a tank without the prop and it shifted normally so it may shift only when running. Maybe I mismeasured the oil amount? Doubt it.

Guess I will take it to the river & try it again.

 

[ba_50]

I wonder if the auto type fuel filter could be Full of water.

 

[KJM]

No problems till now. Only 20 hours on it as far as I know. The transom board looks good. Maybe it is flexing. I put it in a tank without the prop and it shifted normally so it may shift only when running. Maybe I mismeasured the oil amount? Doubt it.

Guess I will take it to the river & try it again.

When you say it shifted normally without the prop, did the prop shaft turn forward and reverse or did the shift lever just move forward and reverse properly? Did you recently change the prop? Not likely water in seperater. Fine filings in oil not a big deal if no larger bits. Its unlikely it's the transom either. Try running her on a hose with the prop on and see what happens.

 

[airshot]

Does the lower unit drain screw have a magnet ? If not get a small pencil magnet and go ibside the drain hole and see if any bigger pieces are in there. When you say little filings, how little ??

 

[ba_50]

I used a large magnet in the drained oil.

It worked perfect on the river today. The plywood transom is rather soft. The clamps were tighten down as much as I could get it today.
Not as strong as I used to be. Guess that was it.

I haven't worked on these things for 3 years so it was a good refresher project.
Thanks for the ideas