OMC 140 Inboard makes whole boat jump like hitting a log???

[JeffKingTulsa]

Should have put it is a 1979. Been running great and now it seems to be getting worse. When I am running along smoothing it will just make a loud clunck sound and shake captain stand and then go again. It is like u are hitting something underwater but I am not. I wonder if the up and down motor wires are shorting and temporarily making the up and down fire at same time but it is a pretty loud baam sound just for an instant. Like a lock in the down position of the motor is giving and then trying to hold again? Any help would be awesome for the big upcoming holiday.

 

[Boomyal]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Have you checked all the lubricants? Sounds like something is getting ready to really break loose.

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

I did the upper and lower gear cases when dewinterizing. Are u thinking there are some things that have the tips that u put the grease gun on and pump up? Ya, unfortunatly, was hoping someone had the same experience.

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Was just reading about clutch pack and worm gear. Clutch is designed to tilt up at 130 to 160 ft lbs in case hit something. I am just familiar with the motor that spins the gear to raise and lower the unit. Maybe this has soemthing to do with it.

 

[Boomyal]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

When moving in forward gear, that outdrive is going nowhere, regardless of the clutch. It will be forced against the intermediate housing and would not be banging back and forth. I do not know how the tilt motor would be getting powered while in motion. Once you are on the water you could pull the tilt motor connector and see for sure.

My thoughts were that maybe you had a broken tooth on a gear inside the drive. That should show up in the oil if it were the case. There are no grease fittings that would deal with what you describe.

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Ya, that is what I was thinking, the force of the motor would keep that tight against boat. But maybe a wave or wake in reverse direction, yada yada, doesnt seem likey I guess.
Yes, I was giogn to just put motor in down position and disconnect the tilt motor so it would rule out the wiring.
Broken tooth and that it is slipping to the next tooth until it breaks. hmmm, bad but plausilbe. U thinking it would show up in which oil, engine(not sure), lower case, upper case?

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

What think about something like motor mounts are broken and the forward gear is pushing motor up till it can't support itself and it falls back down?

 

[Howard Sterndrive]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

A weak tilt clutch will definitely let the drive lift and slam back down when crossing wakes or waves below hull speed. Not sure if it would do it on plane. Someone watching over the transom probably best way to see if that's happening.
A 79 should have the allen screw in the end of the tilt clutch shaft to adjust clutch tension/slip point.

Could be clutch dogs in the lower unit slipping. Check lower unit oil for filings and/or water in the gear oil.

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Thx Howard for the info. Will do on the oil check in lower. I slowed down from a min of at least 3/4 throttle as I thought maybe it would help not do it on the way back. Seemed to have no effect. Thinking what is the worst case that I go for it on holiday weekend and it is clutch dogs and they go bad? Is it they need replaced and so no different than broke ones OR broke ones equal all sorts of bad torn up drive train components.

 

[Howard Sterndrive]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

you need to do some basic visual inspections before going down various what if roads in your mind. Could be ball gears, could be w/p driveshaft, could be engine coupler, could be the prop, could be engine mounts, could be trunnion caps (drive falling off) or a dozen other things ..
grab things, shake 'em
tilt the drive up a bit, hang on to the transom, stand on it and bounce
check all 4 drive fluid compartments and look at the ball gears

don't use the boat while it's doing that - if the drive falls off or the engine jerks loose from a rotten hull you could sink

 

[Boomyal]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

.....A weak tilt clutch will definitely let the drive lift and slam back down when crossing wakes or waves below hull speed.......

Howard, I think if the clutch was that loose, it would not likely even lift the drive. Certainly, if the drive was in the up position you would be able to put your weight on it and cause it to drop.

 

[Howard Sterndrive]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Howard, I think if the clutch was that loose, it would not likely even lift the drive.

One would think so , but no reports of the tilt working properly that I read, but then nothing of a drive lifting in reverse either, so probably not tilt clutch. Quadrant gear could be falling off. Drive could be hanging on one trunnion, or a ball gear is half missing.

with zero preliminary inspection done it's all WAG's

 

[Boomyal]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

........with zero preliminary inspection done it's all WAG's......

Without a doubt. There is certainly a lack of basic analysis here! There are many possible causes that could easily be ruled out or confirmed.

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Thx you two. I wish the boat was just 5 mins away. I am trying to get as prepared for tomorrow as possible. Lets see basic inspection. Prop is new. Tilt works without issues. I will do the leaning and pulling around and watch when it jerks at a 1/4 idle. Its only about 2 beers from the slip to the beach haha.

 

[Boomyal]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Leave the doghouse off when you take it out. I hope that you have someone else driving the boat while you hang out in the back watching for things.

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Working on that now. I have like 4 hours to get there and see if i can figure out something. So a question, if it were a tooth on a gear, there will have to be some MAJOR shavings in lower or upper gear case? If no, suspect they are good(lower unit ok). Check motor mounts.
Is there anything anyone can think of electronically that would cause the sudden BAAM, maybe shift interupter shorting? I just did the whole wiring harness on the motor, wires, points, cap, plugs, all three oil changed, timed, new batteries and ran great all last summer.

 

[JeffKingTulsa]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

It will def do it at full throttle speed! not so far at idle and not thinking no wake zone speed did it. So does that help some of the what could be thories with more detail? I dont think the transom could slide like that and still stay attached. I'm pretty sure its welded. I can feel the thud in the wheel and control box when my hand is on throttle.

 

[Boomyal]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

......So a question, if it were a tooth on a gear, there will have to be some MAJOR shavings in lower or upper gear case? ......

Most likely! Don't forget to disconnect the tilt motor once you are in the water. Yes, watch the motor mounts. Still hoping you have a driver while you are watching?

Sure shouldn't be any thing related to the ignition. And the shift interrupt only grounds out the engine. I does nothing with the outdrive.

 

[superbenk]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

Yikes, that doesn't sound good. Sounds like your slipping a gear or something (as has been suggested). I wouldn't do much with that boat until I knew for sure what was wrong. That could be dangerous or at best strand you somewhere.

 

[Boomyal]

Re: OMC 140 Inboard makes whole boat jump like hitting a log???

....... That could be dangerous or at best strand you somewhere.....

...or needlessly wipeout other components of the outdrive!