is my lower unit bad?

[mtbr00x]

I was out the other day and everything was great until it was time to head in! Of Course!! On the way in we were going about 25 mph when the prop stopped turning yet the motor was running and the temp gauge shot up through the roof. Shift cable seems to work. Now I took my lower unit off and found that bot the shafts are turning when you move one or the other. The engine and OD are OMC 5.7 with a stringer in a 1985 21' sea ray. anyone have any idea what I should do are what it might take to repair this boat?

 

[Gary H NC]

Re: Ok I will try again.

Re: Ok I will try again.

Look for pieces of rubber or black dust around the engine coupler. If it fails it has those exact symptoms.Hopefully your engine compartment will give you enough room to get a light back there and look.
if the coupler goes the drive will not turn and cause the impeller not to pump water,thats why the over heat..

 

[whywhyzed]

Re: Ok I will try again.

Re: Ok I will try again.

Look for pieces of rubber or black dust around the engine coupler.

No rubber on this one Gary, it's an OMC stringer.

A common failure is the w/p driveshaft splines between the upper and lower unit of the drive. There might be enough left that the torque of turning it by hand(if that's what you are describing) is still able to turn it. The engine coupler as gary mentioned could have failed too, but it's a metal to metal spline on your OMC stringer.

EDIT: Just reread that you took the lower off (?- not sure how you did that on a stringer....the cable runs through the upper...) My bet is on a stripped w/p shaft spline. The water pump shaft drives the w/p and couples the power from the upper to the lower unit.
Other possibilities: - Ball gears, intemediate shaft, engine coupler as mentioned, upper gearset

 

[mtbr00x]

Re: is my lower unit bad?

Well I just unbolted it. the cable is still connected. i noticed when i was twisting the shaft by hand that the prop shaft moved, however it was not smooth it was like a dull grinding sound. ok well i am buying a new lower unit and going to see if that fixes it.

 

[philcohen]

Re: is my lower unit bad?

Funny, I just today had a similar problem with my '64 88HP OMC outdrive. Too much torque/RPM's, and it slips...both in foward and reverse. Ball gear seems OK. Where do I start my diagnosis?

 

[philcohen]

Re: is my lower unit bad?

Oops....forgot to mention, it's cooling just fine.

 

[Gary H NC]

Re: is my lower unit bad?

Learn something new every day.Metal to metal coupler..ouch!
Wonder where he will find a new OD...

 

[whywhyzed]

Re: is my lower unit bad?

Funny, I just today had a similar problem with my '64 88HP OMC outdrive. Too much torque/RPM's, and it slips...both in foward and reverse. Ball gear seems OK. Where do I start my diagnosis?

Check the w/p shaft splines- dunno where you would find parts though - a museum perhaps. eBay has actually had a couple of those bullet nose lower OMC outdrives show up in the last year or so.

 

[philcohen]

Re: is my lower unit bad?

Ok...pop and I, (83 yrs, and 48 years respectively), pulled the lower unit apart...seems the spline shaft to the water pump, one side of it, anyway, is roughed up a bit. The wear is only in the center section of the splines, though, and each spline is worn in a cupped manner. I'm not sure it has been actually slipping at this point, though. Any comments?
Also, there's a coupler in the center of the shaft. Is that the metal to metal coupler mentioned previously?
Perhaps I should test the assembly under load on a bench somehow?
Thanks for the invaluable advise, guys!

 

[philcohen]

Re: is my lower unit bad?

Well, after taking the outdrive apart, and load testing each section of the drive train from the flywheel of the motor to the prop, we found the bronze inner sleeve of the prop was spinning in reference to the aluminum outer section. It did not slip in our test, (the first time). Lesson learned. Pass it on.