Logo
FULL SITE MENU

How do I pin point source of vibration

C

cnewton700

Member
96 Mercruiser 4.3lx 6cyl vortec with alpha one gen two outdrive.
I took the outdrive off and installed a new water pump kit. Who ever did it last broke two of the four housing bolts off and left it like that. I drilled them out and mounted the new housing with 4 new bolts. Didn't see any other damage so I re-installed the outdrive and with the muffs on water was circulating fine. It started and idled fine. I launched it for the first time today. Getting under way and got up on plane started out fine but then a loud vibration and shaking started so I shut it down. Ended up limping back to the dock at barely over idle speed. Still vibrating and still loud. I couldn't tell where it was coming from. I checked the prop and found it had about half inch of play in it. It was firmly attached to the shaft so pulling on it moved the shaft in and out about half inch. Is that normal? What is the most common reason for a loud vibration like that? How would you go about finding the source?
 
I would expect maybe 1/16 inch end play.

When you changed the impeller, you will loose gear oil from the upper housing. Did you be sure to refill the drive? To be honest, low oil will ruin the upper housing 1st. No oil will destroy everything.

Pull the drail plug & see what the oil looks like.
 
Some additional information:

The first time I drained the oil I did so with the cap from the reservoir in the engine compartment removed. It was less than half full to begin with. The amount of oil drained was just over half a quart total. It wasn't dis-colored and no metal was present in the pan or on the magnetic screw.I removed the lower half only to change the impeller. Found no damage to the shaft or spline. Only the two bolts that were broke off in the housing which I repaired.I had trouble getting the lower back in by myself so I set it on a stand and removed the upper half.and got it bolted together. No damage to the splines or the shaft and the u-joints movement was fine. There was a small pool of gear oil in the main bellows (maybe 3 tbls) along with the small pieces of rust colored metal shown in the picture. There was no sign of water and the smaller bellows below were dry and clean. I cleaned the main bellows and used a scope to inspect the bellows and the gear the shaft goes into. Didn't see anything broken or torn so I rented a crane and put it back together., launched it, got up on plane and forced to shut it down and idle back to the dock due to the loud vibration and rough running.At no wake speed it was louder than usual but very little vibration.
bellows.jpg
 
As asked or mentioned earlier, when you separate the two halfs once back together did uou refill drive??

How to do it properly,

you remove lower plug and upper plug (both are slotted screws) lower near cone of drive and upper on left side just below top of drive. You now add gear oil from the lower hole til it leaks out of upper hole then install plug. Carefully remove fill line from bottom hole and insert plug. Making sure both have ring gaskets and they are tight. Then top off gear resevior which will drain down to about half after running as it fills upper gear case. At which time top the resevoir off again.

Sounds like you did not refill drive????

If you did not the there is a good chance the drive is toast
.
 
I've only had it for a couple months. It was stored outside for at least 5 years and needed everything the sun could destroy seats. wall panels, engine cover and any exposed wiring. It showed less than 200 hours on it, started and sounded good. I did all the upholstery myself, and replaced the damaged wiring, water hoses... What I described above happened the first time I put it in the water.
 
Ayuh,... Is the motor skipping,..??
Fire it up, without the drive, to whether it's the motor, or the drive,....
 
Back
Top