bobby daniels

Sorry guys my experance has been load (holeshot),, dried rubber,lack of lube ,any of the above ,,,,mainly ITS the load on the newer hubs THAT sheers the rubber from the center ,sorry you had the trouble

cig1988

Mercury suggest a special spline grease just for this. I would imagine those high dollar engineers developed that grease for a specific reason. Note there are 2 grease fittings on the coupler. Grease them both every several weeks.

Tinkerer

I grease my drive splines every year when I reinstall the drives. ( in the spring ) I have NEVER lost a hub yet from lack of grease or from LOAD. I have aligned MANY engines and have seen MANY blown couplings and they were all from missalignment. I lock down the rear engine mounts using washers in place of the fiber one. This keeps the engine from twisting. I have had problems with blowing couplings with what I thought was a properly aligned engine, ( the tool slid right in ) But the truth is that it was way off due to the fact that the rear mounts had sagged. Even with bad rear mounts you can lower the front mounts and still get the alignment tool to go in smooth.

US1 Fountain

TB, I don't understand your post. I seen you mention this before, but just can't comprehend it.
If the rear mounts sag, wouldn't that just mean that the front of the motor would have to be lowered even more in order to have the alignment tool go in? It would seem that the only thing changing, would be that the gimble bearing would now have to have the center race tilted downward, possibley to the point of bearing failure 1st??? And possibly working the U-joint a bit harder?
Thanks,
Jerry

mcollinstn

Lack of grease and alignment under load are coupler-killers.

Holeshot is a drive-killer.

2 of the 3 drives I've popped have been during holeshot on an 8500 pound boat with twin 502 mags.

I now NEVER open the 4 barrels under 30mph. No real need to, as boat comes out plenty fast without overstressing.

outlawntexas

bikinilover, IBC in Mabank is doing the work. There were 2 ahead of me so I hope to have it in another week.

The rest of you guys, thanks for all of the info. I have learned a $hitload from you all. Clearly I will need to find a way to get to those grease fittings regularly.

Thanks,
Bruce...

OPIE272

Just look at this way. The drive lines up with the gimble bearing.
The engine lines up with the gimble bearing.

Then everything is fine...Right? Maybe?

Aim your rifle scope with your eye and the cross hairs in the scope now line the target with the cross hairs. Now just reposition hour head just a little bit.
Does the target seem to move? Your alignment is the same.

The alignment of your motor is just one step more difficult. It has a 4th point.
1. outdrive
2. gimble bearing
3. back of coupler
4. front of coupler

Your thought of just dropping the front of the motor a bit would be correct except 1 thing...The outdrive


So if the motor shifts in any direction the coupler will take the brunt of the damage. The coupler was designed to dampen vibration and adjust for "Minor" deviation. But not major alignment problems.

If a coupler is damaged by spinning the rubber out (Like a Prop) (That's why we go to solid hubs)then it was either age, faulty, or horsepower.
With engines running over the 600 H.P. range with no problems then I don't feel 400 H.P. "Put too much to it"
Does that help? Or is this still clear as mud?

CESSNA

GUESS its just faulty ??
some people get 400 hrs out of a 500 efi and no problems others get only 100 from the same type motor guess its the nut behind the wheel or faulty..
it could be alignment maybe,,, but load (HORSEPOWER) gets my vote ,its just a big sheer pin .

Pure Energy

After 90 hrs. it is not HP.

Tinkerer

I have blown a coupling in 30 minutes due to alignment. I had a SBF putting out over 500 HP and it started blowing couplings. I replaced the first one and checked the alignment -- all ok -- Blew the second one in 30 minutes of normal hot rodding. Replaced it again and the alignment was right on. Blew that one again in the same amount of time. Took it to the marine repair and they tooled it and said it was perfect. I then tore into it to find what the problem was. After much measuring and checking I found that the rear engine mounts were sagged and because of this I had the front of the motor pointing down to compensate for the sagged mount and this also will let the alignment tool slide right in but the angle of the input shaft is not parallel with the top drive shaft. ( they have to be parallel or it will put sideways torque on the coupler) It is this sideways torque that tears up the coupler. The trick is when the tool is in place it must come straight out the back not tilted up. It is a learned thing to look for. They used to make a plate that went over the shaft that fit into the bell housing. If it did not fit flush your alignment was off. I can do it by eye now. I now lock down the rear mounts using washers above and below the engine (ears) to lock in place. This way the engine can't twist and get out of alignment when the power is on.