lower unit stopped driving

[mwbaughan]

Was running 4500 rpms with my 1980 V200 Merc when it sounded like it was
thrown in neutral. Lucky that it did not blow up from over rev.

It shifts in to forward and reverse with no clunk and no prop spin, just revs up.

When in forwerd gear with the motor off, the prop locks as the lower unit is in gear, and spins freely in neutral. The pump is turning evidenced by a good water stream, but the gears are not?

What do you think this is? Next steps?

Thanks.......Mark

 

[mthieme]

Re: lower unit stopped driving

My first guess would be a sheared drive shaft near the bottom just above the splines where it is chamfered...but this is just a guess.

 

[mwbaughan]

Re: lower unit stopped driving

My first guess would be a sheared drive shaft near the bottom just above the splines where it is chamfered...but this is just a guess.

That makes sense. This was a completely rebuilt unit with new gears. Ran it
for about 3 months / 600 miles.

That outfit on ebay is selling new aftermarket v6 lower lower units for $795 plus $45 shipping. That may be a smarter way to go instead of shaft replacement?

Thanks.............Mark

 

[mthieme]

Re: lower unit stopped driving

I'd pop it apart to be sure.
Buying a complete lower unit isn't going to do you any good.
The drive shaft connects into the lower unit. It runs about $75 (if memory serves).

 

[Chris1956]

Re: lower unit stopped driving

Mark, Are you sure the prop hub is good. Sometimes the prop cannot be turned by hand, when motor is in gear(engine off), but under engine power they slip. The test is to mark the prop hub and prop with a sharpie. Then reinstall the prop and run the motor. If the marks move in relation to each other the prop hub is spun.

 

[mthieme]

Re: lower unit stopped driving

He originally posted "no prop spin".

 

[mwbaughan]

Re: lower unit stopped driving

When I tried to spin it by hand it did not spin. Pretty sure it is a sheared shaft, but won't have time to drop it till Saturday most likely.

I understand that the shafts are much higher than that and you need to reshim the gears when installing requiring several special tools. That is the only reason I a considering that new unit for $800 if the shaft is broken.

Thanks.......Mark

 

[mwbaughan]

Re: lower unit stopped driving

Well I finally got out there and dropped the unit. Shaft is not sheared.

Maybe it is the hub, but I can not turn it by hand when in gear with motor off.

Also no clunk at all when running and it is put in gear. Could something be soun where the top of the shaft engages the power head?

I will take a look at the hub tomorrow.

Thanks................Mark

 

[mwbaughan]

Re: lower unit stopped driving

Actually the shaft does spin when in gear. I pulled the water pump assembly off and the shaft spins easily and wobbles so I assume it is broke.

Will start another post on what to do next.