Need some help

[Arie S]

My son finaly got the engine installed and running in his donzi. The motor sounds very strong but has a very bad vibration. We worked on it all day and got most of the kinks out of it except for the vibration. We were wondering if it could be a compatibility problem. Something seems out of ballance. We are running the engine on a hose and the outdrive is not installed. All the bearings and seals were replaced in the gimble housingWe aligned the engine again and seems to be with in 1/8 inch flywheel housing and the gimble housing gap. The boat originaly came with a 383 stroker and volvo 280. He installed a 260 mercruiser and kept the volvo outdrive. our questions are


1 are there any problems mating a mercruiser motor to a volvo drive 2 is the stroker flywheel different than a 350 Flywheel
3 Can the flywheel (volvo) be out of ballance and how do you check that
4 what could make this engine vibrate so bad that anything not bolted down dances all over the place.

THe boat is otherwise ready to go into the water but I dont know what else to look for without pulling the engine again. Any help woulb be great Thanks John

[thehow33]

sounds like your flywheel is off balance

[Conquistador_del_mar]

If you used the 383 flywheel on the 260HP regular 350 block motor, that is your problem. The 383 uses an externally balanced flywheel while the regular 350 does not. Bill

[Phil S]

+3 on flywheel balancing...

[Planetwarmer]

If you used the 383 flywheel on the 260HP regular 350 block motor, that is your problem. The 383 uses an externally balanced flywheel while the regular 350 does not. Bill
So, can he mount an external balancer on the motor without pulling the whole motor?

[mrfixxall]

So, can he mount an external balancer on the motor without pulling the whole motor?


Nope! :) motor has to come out!

[mrfixxall]

nope! motor has to come out..:)

John dont run the engine like this or you will end up with the connecting rods in the bilage..

[Conquistador_del_mar]

So, can he mount an external balancer on the motor without pulling the whole motor?

No. An engine must have the correct flywheel and harmonic balancer. If an externally balanced flywheel is installed on an internally balanced motor, the only correction is to replace the flywheel with the correct one. Bill

[Arie S]

We pulled the engine and removed the flywheel. How do you tell them apart. This one has some really big holes drilled into the back. Is this how they ballance the motor by removing weight from one side of the flywheel? I have a mercruiser flywheel from another project It is the same size 12 1/2 inches and it looks like the flex plate will bolt right up. Is it ok to use the merc flywheel or are we asking for more problems. Thanks for all your help John

[MOP]

Flywheels can be a bit confusing, most stock setups use an externally balanced flywheel with a harmonic balancer. Internal balancing costs money and is not needed for normal use, it is cheaper for a mass engine manufacturer to get the weights of the internal close then throw on a flywheel and harmonic balancer to keep it nice an smooth. One of the first things any hot rodder does is to blue print and balance an engine, like I said that costs. My Lunati Pro Mod kit 383 uses a -0- balance flywheel, it is internally balanced the crank shaft by its self was $1,500. In stock engines this is not practical to balance and make them an affordable engine.