Hey Spareparts
 

Ive got a little vibration when im running along slow to mid throttle. The outdrive was completely rebuilt before I got it. The U joints and all were replaced. I rebuilt the engine, engine bed stringers and transom, installed engine and lined it up using a merc alignment tool. It slips in really easy, so i believe it is correctly aligned. Could the imput shaft be out of balance? I can trim it up when it gets up on plane and it smoothes right out. If I trim it back down it grumbles a little. Forgot to tell ya I rebuilt the whole gimble section, new gimble brg. boots, hinge pins,top and bottom swivel pins and brgs. What do ya think, it feels like the imput shaft is out of balance or something. I dont want to screw up what Ive already done!

one of the problems they had with those big 4 cylinders was that they did vibrate at lower rpms, is this a new vibration? one that wasn't there before? Or has it been doing it all teh time? A couple of things to check is the front and rear motor mounts. Make sure the rear are tight and the front lags are still secure, check that single isolater on the front mount, make sure the nuts haven't vibrated loose or teh isolater itself is bad. Use a pry bar and see if you can move the engine up and down from the motor mount.

If everything checks out OK, I wpould suspect the coupler, next time you have the drive off, stick the alignment shaft in the coupler, then rotate the engine 90 degress and check it again, do it 2 more times. mercury told me to crank the engine(with a water supply hooked to it) while the alignment tool was still in place, and check it for wobble. you can really fine tune the alignment this way.

Thanks Spare, The rear motor mounts are new, the front one is original. When I aligned it, I turned the engine over 90 degrees and checked it again and one way it was a little tighter than the other. Its probley the coupler. Everything else is new. I noticed it the first time I started it up after the rebuild. Its not terrible but noticeable, It makes my old compass spin round and round.

those couplings aren't the most precision things around, you could replace it with a new one and not get a bit better. If everything checks out, just keep running it. remeber, 4 cylinders can't be completly balanced without a balance shaft. The big 224 cu in motor of yours can shake your fillings out when everything is perfect. Just thought of one other thing, are you having any charging problems? I've seen the magnets in the balancer slide around and cause problems, it could throw the balance off. Whenever I change one out to an altenator, I allway knock the magnets out berfore replacing the balancer

Well it cant be that, it had been converted to an external alternator before I got it. I recently changed out the camshaft seals and checked the back of the harmonic balancer and the magnets were gone. I just looked on a Breezeworks site and found a 97432A1 coupler for 109.00. Thats less than half of everyone else. Do you know if these are used or not? Id rather have a new one if I got to go through all the trouble to install it.Most are around 209.00. Do you know of any cheaper new ones? Thanks Spare!

The 250 SEARAY I redid last year would vibrate pretty bad as well when trimmed in hard. Smoothed right out when you trimmed it to a neutral position. This was with a V8/ALPHA 1 combo.

Ferm brings up a good point, most boats will create a resonance when trimmed all the way in, I don't know if its cavitation or just vibration going thru the drive, but once you trim it a little, it quiets down, certainly would be cheaper than any other solution. How bad is this thing vibrating? Is causing you mixer to go flat? Rattleling the wax out of your ears? or just a slight annoyance that you notice only because you worked on it

It rattles anything light laying loose in the boat like a fishing rod laying up against the gunnel. Its really not terrible but definately noticeable to me and others in or out of the water. It makes my old Ritchie compass spin around. But after I get underway I trim the drive up till the bow almost bounces and it goes away. My buddys 86 v20 with the same motor and drive is smooth as silk all the time. If I can get over Christmas I might buy me a new coupler and change it out. I dont think it will be to bad of a job. I think I can do it without pullin the motor out, just support the rear , pull the outdrive and crawl back there and unbolt it. Probley gotta pull the bellhousing off.

pull the drive and make sure you don't have one of your u-joints binding, while you have the drive off, try the alignment shaft/engine running trick

Ive checked the u joints, the're new and move freely. Ill try the alignment tool,wobble thing when I pull it next time. Thanks Spare!