Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

[jaknkoke]

I have been posting for a couple days and through help have solved my last issue. Spun prop hub. Here is a new one. Please help!
At 4000-4300 rpms I get a horrific vibration that makes me immediately drop throttle to idle. Most of the time it goes away at idle and I can accelerate again to below 4000 rpms. At times it does not go away at idle or even when I shift to neutral! I have to turn ignition off and restart. So I am assuming this problem is ahead of, or toward engine from whatever clutch system there is in these things. (I am a complete rookie when it comes to boats and am not a good mechanic by any means with a car! By the way, I took off top plate of outdrive under dipstick and noticed the bearings under that plate have flat spots almost all the way around. Thought I'd mention this. Dont know what these bearings are for or what they may have to do with my problem.
Thanks for any help you may be able to give.
Jaknkoke--

 

[Walt T]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

Probably a coupler coming apart, but I would think you would hear it too.

 

[captmello]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

I think its time to pull the upper gear box and have a look. So you say you're not a good mechanic...Do you have tools? Here's what it takes to pull off the upper gear assembly.

http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/outdrive-side-pin-removal-309095.html

 

[jaknkoke]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

looks simple enough mello. Appreciate the link. When I pull the upper gear box, what exactly am i looking for? are the flat spots in the larger bearings that I see on top a problem or is that normal in these things? also, does it make sense that I, at times, actually still have the bad vibration when idled all the way down and even when in neutral? Are the u-joints and/or bearings in upper gear box sill moving when I am in neutral?
Thanks again for your input.
Jaknkoke--

 

[captmello]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

this pic show hos to remove the pin in the helmet. Use 1/4" bolts in the two side holes to jack the pin up out of the helmet. This can be a sticking point for many when removing the upper. Its not hard, just kind of odd.

Once the upper is off, you will be able to examine the ujoints and drive shaft. Those are both spinning whenever the motor is running and can cause vibration.

I'm not sure about the bearings you are looking at. Flat spots??? I don't know how they could get flat spots on them. Can you take a pic? The top cover rarely needs to be removed...

 

[jaknkoke]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

thanks chief. What does the coupler couple? u-joint to shaft? I did here something pretty high speed and harsh that sounded metalic bouncing around inside somewhere a few days ago. only lasted about 3-4 seconds and then disappeared.

 

[jaknkoke]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

Yes Mello, I will take a pic this afternoon. Your advice is much appreciated. I just took the upper gear cap off while doing a little investigating. Assumed those bearings that are immediately visable once cap is off should be perfectly round but they are fairly uniformly flattened on top. I'll take a pic later this afternoon

 

[jaknkoke]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

Well, I believe I have found the problem. If not, it is definitely another one! Here are the pics. I am sure you can see the metal shavings of the housing just behind the spline coming off the engine that connects to the u-joints. The shavings are coming from the out of round and warn down housing. What now? Is that housing something I can replace? What is it called and where do I get it?
Thanks again.
Jak--
I am having trouble attaching the pics I took. Hopefully you can understand what I am looking at from my description. I am looking at the spline coming through the transom at the back of the flexible boot I pushed back to remove upper gear box. by back I mean toward the motor. Out of round housing is surrounding this area I think about 3-4" in diameter.

 

[Scott Danforth]

Re: Major vibrations at higher rpm 1992 volvo penta 250a and 280 outdrive

get a photobucket account and link the pictures