Hydraulic vs mechanical gearbox.

[oldcal46skipper]

I completed Marine Transmission school about 45 years ago. We started cruising in our Cal 46 in 1988 which was launched in 1967 and had 11,000 hours on the engine and Borg Warner Velvet Drive. I rebuilt in in 1987, follow routine maintenance procedures and now have another 3,600 hours, No problems!


When we settled in Pensacola, I started my business again repairing Perkins engines & BW Velvet Drives. I rebuilt a few Hurth & other mechanical gears, but stopped when the parts & labor to rebuild one cost the same as a new ZF. I would not have one on any of my boats! You may be lucky enough to get 1,500 hours on a mechanical gear. Contact me off the forum for more details and pictures.

[Compass790]

Following this thread with interest,
Only have experience with mechanical but maybe easier for DIY to fix. I certainly found our Kanzaki mechanical box simple with virtually no wear on the gears, after maybe 2000 hrs I'd stripped it to check. Only an 8hp motor tho. My thoughts are similar to post#15 but the auto transmission in my car goes good after +300,000km so no complaints about hydraulics as such.
I think you need to ask your question as to the specific gearboxes which are your options. You need posters who have done hours on those types of gearboxes.
Let us know what you decide & why please

[RaymondR]

Originally Posted by chrisr

I have always had mechanical gearboxes, however did charter a canal boat in europe a while ago, with a hydraulic g'box...and it was an eye-opener for boat handling

the ability to go from full ahead to full astern as fast as you could move the lever was impressive, and allowed one to turn a 55'single screw in not much more than it's own length

of course there are other issues, however hydraulic has (apparently) a big advantage in boat handling.

cheers,

Hell of a houseboat with a 55 foor prop.

Yeah I know you didn't mean 55 foot but I couldn't help myself.

[GILow]

Originally Posted by DougR

First off I would suggest that which ever gear you select, you study the rating sheet for the gear in question.....





....

Hope this point out a few items and maybe raises a few questions for you.



DougR

Great list, and really helpful comparison, thank you.

At least in this case I’d be taking either of the “standard” offerings from Beta or Nanni, so I will trust them to match the capabilities of the gearbox to the engine.

Having a feathering prop will be a bit of a bonus, as I am assured it is happy with both types of gearbox and at least I won’t have the freewheeling problem that seems to be an issue for some models.

[Jim Cate]

t least in this case I’d be taking either of the “standard” offerings from Beta or Nanni,

Matt, at least in the case of our Nanni, both the zf10 and the zf15 were offered as options. I wish that Gary had opted for the 15! (Actually, these were the Hurst predecessors, not the ZF but ya know what I meant!)

Jim

[GILow]

Originally Posted by Siberian Sea

I installed a Beta Marine with a Twin Disc hydraulic gearbox. Had these for years in my commercial fishing boats in Alaska. Fishing operations would work the hell out of the gearbox and never never did I have a problem. Honestly an Alison or Twin Disc gearbox is second to none. These are good for the life of the boat. Yes they are big and heavy but, just like your anchor gear it’s something you never want to fail.

A mechanical Twin disc is listed as a standard option for the Beta, I will put this on my short list. I am hearing a lot of positive stuff about the Twin Disc.

[RaymondR]

I used a mechanical Twin Disc gearbox behind a 50 hp Kubota diesel in the 2010 re-powering of my previous boat and so far it has been fine. It has a cooler built in and was manufactured in Italy.

From a mechanical engineering viewpoint I have a philosophical problem with low power gearboxes using a more complex scheme to hydraulically engage clutches. Different matter with high powered equipment.

[GILow]

Originally Posted by RaymondR

I used a mechanical Twin Disc gearbox behind a 50 hp Kubota diesel in the 2010 re-powering of my previous boat and so far it has been fine. It has a cooler built in and was manufactured in Italy.

From a mechanical engineering viewpoint I have a philosophical problem with low power gearboxes using a more complex scheme to hydraulically engage clutches. Different matter with high powered equipment.

One more vote for the twin disc then. [emoji106]

[skipperpete]

It needs to be mentioned that the yacht size "twindisc" gearboxes made In Italy bear no similarity other than the name to the "tough as nails" deep reduction hydraulic gearboxes so often used in heavy duty commercial vessels. The US Twindisc was a very well made reversing gear and even had a "get you home" clutch lockup in case of hydraulic or clutch failure.
The Italian product was originally called Technodrive and at some point magically became Twindisc and then TMC

[nauticalnomad]

I replaced my engine and gearbox with a Nanni hydraulic propulsion.. Ive had it for 3 years now... I have zero complaints.. The hoses if changed every 5 years or so wont be an issue with leaks etc.

[GILow]

Originally Posted by skipperpete

It needs to be mentioned that the yacht size "twindisc" gearboxes made In Italy bear no similarity other than the name to the "tough as nails" deep reduction hydraulic gearboxes so often used in heavy duty commercial vessels. The US Twindisc was a very well made reversing gear and even had a "get you home" clutch lockup in case of hydraulic or clutch failure.
The Italian product was originally called Technodrive and at some point magically became Twindisc and then TMC

So you’d take the ZF offering in preference at this HP?

[smacksman]

We had a Perkins 238 in a 40ft sailboat. It came with a larger flywheel apres fitted to drive an alternator for re-gen charging under sail. This cooked the hydraulic gearbox as with the engine stopped there was no lube oil feed to the grarbox. With a new M90 Perkins fitted we arranged a shaft lock on this big flywheel (it was on the prop shaft, not the box) and that stopped the big 4 blade fixed prop from turning the box under sail. The shaft lock was a bit clumsy and took a while to release so was a rush when you wanted the engine in a hurry.
So for my 2c, hydraulic is ok for motor vessels but a mechanical box is better for a sail boat.

[Captain Steve]

If you go hydraulic, I think you will find you need a shaft brake to stop the shaft from turning when you are sailing. Shaft turning when the engine is not running and pumping hydraulic fluid is not good for the hydraulic transmission.

My 1985 AMEL Sharki was factory designed for a prop shaft generator, so the shaft is always turning when I sail. I have 45,000 NM on the boat and 6800 hours on my old Perkins. The original Hurth mechanical transmission is three sizes larger than normal for a Perkins 4108 and is still running fine (as is the old Perkins!).

[sailorxyz]

I think Hurth boxes get a lot of bad rap because people put undersized boxes in. I've had a Hurth HBW150 for over 20 years in LC (my old boat) and it never gave problems of any sort. I changed the ATF at the recommended intervals but nothing else. It's coupled to a 36hp Mitsubishi conversion that likewise has never given problems.

[Visarend]

I have a very good experience with a hydraulic PRM 120, on my Ford 48 HP since 30 years. lots of motoring in the Med in summer, sometimes for 5-6 days at a time. This year it lost the oil, which became apparent only controlling the bilge, it still went on, with no need to operate the mechanical take me home trick. The oil leak is due only to a seal, but it is probably the moment for remotorising the boat.