Hurth Transmission Noises?

[E4ODnut]

We're in the final stages of purchasing a '93 Bayliner 3288. 351 Fords with Hurth transmissions. We were out for sea trials today, and there are some transmission noises that concern me.

The engines were brought up to operating temperature at the dock before heading out. When put into gear, both transmissions had quite a pronounced rattle. Port slightly worse than starboard. Reverse slightly worse than forward. The noise decreased as the throttles were advanced. After trials were over, and the transmissions were fully warmed up, the noise had decreased, but, was still there.
Both transmissions go in and out of gear smoothly, with no hesitation. There is no noticeable vibration in either gear, at any speed.

Any theories as to what the cause might be?
Is it serious, or just the nature of the beast?
If serious, what would be an estimated repair cost?

Thanks,
Robert

[gonzo]

How do you know the noise was from the transmissions? A badly tuned or missing engine will cause that noise. It is the backlash of the gears.

[FAST FRED]

Foley Marine in Mass is the source for Hurth tranneys and parts.

These are relativly cheap (1/5 of say a Twin Disc) so you might just figure in the price of a new set.

Since they seem to have worn out rapidly , you can sometimes get a bigger power handling tranny that fits in the same space, just ask.

FAST FRED

[E4ODnut]

Update:

I did a bunch more research, and was even pointed to a directive from Hurth/ZF. The concensus is that as long as the noise is gone by 30% RPM under load, it's normal and quite acceptable. The noise is caused by irregularities of torque and rotation on the necessary gear backlash, and will differ depending on installation. It's unfortunate, but quite common and not bad enough to go on a long and tedious quest to try and eliminate, or at least reduce it.

Thanks for the responses,
Robert

[nevd]

If you have not already done it, I strongly recommend sampling the oil in accordance with the recommendations of a modern analytical/sprectographic laboratory. While you are at it, I'd also cover the engines.