OMC 800 Need Help Diagnose

[ezgon]

Hi everyone,new here,but from what I have been reading, sounds like a great group of people. Well here's what happen, just got out in the water and went to power up had the nose in the air and something went out of the sterndrive. No rotation of prop. Whining noise from top of sterndrive,then the engine started to warm up. Go's in out of gear realy easy. It's a 79 mark twain,351 motor, omc 800 sterndrive. Does any of this sound familiar? Need some advice on what to look for, before I start tearing it down. Thanks in advance.

 

[cr2k]

Re: OMC 800 Need Help Diagnose

Engine coupler
Ball Gears
Drive shaft
Drive gears in upper
Dogs in lower
Prop hub

That just about covers it top to bottom. But you can go bottom to top too.

Drain all 3 cavities...Intermediate, Upper, Lower, and check for metal.
very small amount in fine pieces normal for lower.

 

[futz]

Re: OMC 800 Need Help Diagnose

for sure not the prop. for sure not the dog, cause it's electric shift. And if it was a hydro-mechanical unit, the dog would still not be the problem.

1- Put the boat in forward, and step on the prop, clockwise if the prop turns and the ball gears do not move? It's the water pump shaft.

If the prop turns, and the ball gears move it's the coupler. Simple as that.

 

[WizeOne]

Re: OMC 800 Need Help Diagnose

A '79 will be a hydro-mechanical drive. I really doubt that anyone would have gone backward and installed an electric shift leg. The unit would most likely have a decal on it identifying it as an 800. Electric shifts were not 800's.

With the whiring sound and no forward and reverse I would vote for a stripped water pump shaft. I would still inspect the ball joints though and remember to NEVER (10-15% only, at low rpm, for shallow water emergency) drive with that unit tilted up.

 

[futz]

Re: OMC 800 Need Help Diagnose

'78 was first year of hydro-mechanical units, had a brain fart.
still the same tests though.

Thanks Wizeone

 

[ezgon]

Re: OMC 800 Need Help Diagnose

Thanks futz, stoped and checked it out on the way from work, put the shifter in forward position and turned the prop and u could turn it either direction an the ball gears didn't move.Drained all three cavities but didn't find any shavings. I changed all the oil this spring. So would I need to pull the whole unit off to check the waterpump shaft? Or is it just as easy to tear apart on the boat? Do I want to work from the bottom up, or from the top down? And where should I unhook the shifter cable at? Behind the motor or at the lower unit? I know, alot of questions, but that's how u learn.

 

[futz]

Re: OMC 800 Need Help Diagnose

you have a manual? have a table or a large cooler or chair ready on the port side.

on a trailer lower the bow as far as it will go, and raise the drive 1/2 the way up.

Remove the very top bolts, and the exhaust and the lower will come down. place it on the table and tie it to the swim platform. be carefull of the cable don't pull on it plenty of play in the cable.

remove the 4 bolts facing u in the upper drive from the bottom and the whole waterpump and shaft will come out. you could raise the drive a little more to make it easy, i sit on a milk crate when i pull the pump.

 

[WizeOne]

Re: OMC 800 Need Help Diagnose

.....Drained all three cavities but didn't find any shavings. .....

Actually the splined joint that most likely stripped does not sit in oil. That is why there is no evidence of metal in the oil. That is also one of the reasons that it strips in the first place. You grease the joint when it goes together and there is an Oring on the male that is there to keep the grease in....but after years of service, the grease still dries out and goes away and allows the splines in that connection to hammer themselves into oblivion.

 

[ezgon]

Re: OMC 800 Need Help Diagnose

Well were going to find out in the morning, thanks for the reply, so if I can get it out without taking the cable all the way out would be a plus. I downloaded a manual that Don put up and a dia. of all the parts so it shouldn't be to bad. See how tomarow goes. I may be back with more ques. Have a good weekend,,

 

[Howard Sterndrive]

Re: OMC 800 Need Help Diagnose

I would vote for a stripped water pump shaft.

+1
............

 

[supercab78]

Re: OMC 800 Need Help Diagnose

I feel your pain! I've had to do mine twice in 23 years. If it's the shafts, it's a pain. I'll give you a trick for getting your bearings back on your shafts. Put your shafts in the freezer for a hour or so and the bearings in the oven. At 350 til done : ). The bearings will sometimes drop onto the shafts for you.

 

[WizeOne]

Re: OMC 800 Need Help Diagnose

I feel your pain! I've had to do mine twice in 23 years. If it's the shafts, it's a pain. I'll give you a trick for getting your bearings back on your shafts. Put your shafts in the freezer for a hour or so and the bearings in the oven. At 350 til done : ). The bearings will sometimes drop onto the shafts for you.

So-----How is it that you get the bearings off the shafts?

 

[futz]

Re: OMC 800 Need Help Diagnose

Did mine was the most unremarkable part of the whole process.

 

[ezgon]

Re: OMC 800 Need Help Diagnose

Ok guys this is what I've got done so far. Got the water pump shaft out, and guess what, all the splines were sheared off. Then looked up in the upper drive shaft and of course the splines on it were shoot. So how in the world do u get the bearing housing an shaft out. Do u need to pull the upper horizontal out? Dosn't the bearing housing come out the bottom with the shaft? If I can get that out, I can take it in an get new bearings, shaft and all the rest of the stuff fixed.

 

[futz]

Re: OMC 800 Need Help Diagnose

Should come straight down, actually it's supposed to be all one piece. Grab the shaft with a pair of pliers pull it out.

 

[supercab78]

Re: OMC 800 Need Help Diagnose

Wizeone; If I remember correctly I used a automotive type bearing press to remove the bearing. My bearing were still good both times so I reused them.