Repeated Gearbox Failure Caused By Prop?

[Jumbalara]

Our 34' sloop has a 22hp Kubota coupled to a Hurth HBW150-2,1RV vee drive gearbox. We are currently stuck in Noumea while the gearbox gets rebuilt. This is the 4th time in 2 years. Rebuild number 3 was in Sydney and got us here via Brisbane, a grand total of 300 engine hours. The repairateur here is suggesting that it might be caused by our folding prop. Apparently Volvo refuse to warranty their gearbox if used with some folding props. Our prop is a 3 blade folding prop made by Seahawk in Melbourne. Admittedly it is a fairly chunky unit, but I wouldn't have thought it would bother a gearbox which is rated up to 55hp. Has anybody seen gearbox failure due to a folding prop before?

[CS Cruiser]

Interesting, sorry to hear of your trouble will be watching thread.

[NoTies]

What part of the gearbox is failing?

[roverhi]

What does the manufacturer recommend for gear position when sailing with engine off?? Do they want the gear shift in neutral so the prop can spin or in gear, probably reverse, to stop the rotation. Not as big a thing with a folding prop if it is indeed folding and not trying to turn the shaft. May be the cause of problems. Yanmar wants the engine in neutral with the prop allowed to spin or fixed with a shaft brake. Others want engine in gear so the prop won't turn.

[Jumbalara]

The first 3 failures were thrust plate wear.
Hurth manual says sail with reverse gear selected. The prop does fold, so once you stop it turning it stays stopped.

[MarkSF]

I just read the HBW 150 manual, it states the lever should be left in neutral.

http://www.iwabss-limited.co.uk/upload/hurth_manual.pdf

I always leave my HBW 50 in neutral.

[NoTies]

Originally Posted by Jumbalara

The first 3 failures were thrust plate wear.
Hurth manual says sail with reverse gear selected. The prop does fold, so once you stop it turning it stays stopped.

Wear on the front side or rear side of the plate? Ie, on the forwards propulsion side or astern.

[sailorboy1]

You sure your prop is matched to your drive train far as power rating?

[TurninTurtle]

Sure the prop is actually folding and not spinning the shaft?

"Thrust plate wear" wearing out says something is spinning.

[Uncle Bob]

Had a hurth in my boat when I got it, lasted 800 hrs before slipping, I replaced it with a PRM after the engine builder said he no longer used Hurth because of the problem. And for just a little more than the cost of the Hurth rebuild.

[Jumbalara]

The prop is slightly oversize compared to theory. Definitely nowhere near as big as the prop on a 55hp motor would be. (the gearbox is rated to 55hp). The max revs for the motor in neutral is 3500. With the prop engaged it gets to 2500 and blows a little black smoke. Normal cruising speed is 2100 rpm.
When sailing we normally put it in reverse just to stop it spinning, then leave it in neutral. Once the prop stops spinning it folds and stays stopped.
There are 2 separate thrust washers, one for forward, one for reverse. So far it has always been the forward washer that wears out. Logically, for the thrust washer to wear, the clutch must be slipping either during the engagement process or under power.
I would gladly swap for any other make of gearbox, but haven't heard of a vee box the right size for us. Changing to a straight drive would mean shifting the motor into the middle of the cabin.

[NoTies]

I can't see how a slipping clutch would cause thrust washer wear and it is unlikely to be a problem when sailing with engine off because the load would be on the astern thrust. I would be having a close look at shaft alignment as well as radial and linear runout of both coupling flanges.

[sony2000]

Try to buy another transmission to keep as a spare. It may also prove if yours is prone to failure. Leave the transmission in reverse. A folding prop will turn in neutral. It won't spin, but it does turn.

A reality of VeeDrives is that they are always at a greater angle of drive than standard drive shafts. And often their owners or mechanics mess up on just how much oil they put in housing. Often they can be under oiled, or should we say, they should be filled to the maximum allowed, especially when operating for long periods.
Oil cooler, change oil more often, optional higher SAE grade, etc.

[jimbunyard]

It's a long shot, but on page 38 in the manual Marksf references in post 6 above they specifically say that the thrust washer goes one way, with 'the sintered brown face towards the gear'. Is it possible that they're putting the T/W in backwards?

[dick sargent]

Sounds to me like it might be
caused from sloppy engine/prop shaft alignment.