Technodrive or PRM - which is better?

[Paragon]

Now Harry Hill would say "FIGHT"!!!!!!!!!!!

I'm looking for a more educated and experienced response. If you had the choice of these two gearboxes to put on an engine (TMC40 or PRM80) which one would you choose?

There is no price differential between the boxes and the engine is a Beta 20.

 

[sailorman]

Now Harry Hill would say "FIGHT"!!!!!!!!!!!

I'm looking for a more educated and experienced response. If you had the choice of these two gearboxes to put on an engine (TMC40 or PRM80) which one would you choose?

There is no price differential between the boxes and the engine is a Beta 20.

i have the PRM with 800 trouble free hrs to date

 

[RogerMayne]

PRM

PRM is the winner! Made in Coventry Great Britain, I have one on my boat, performed without fault for the last three years (unlike the ZF-Hurth it replaced).

 

[Paragon]

So that's two - nil to PRM!

 

[Caer Urfa]

So that's two - nil to PRM!

Hi Merry Mary!!

Not an expert on the TMC40 box, But recently I checked out a PRM80 box for a member after being recommended it to replace a Hurth HBW 50 - R2 Gearbox by a well known on line supplier.

On checking the drawings I noted the PRM 80 box 'drop' (drive shaft in/out) is 10mm differance, which does not sound much until you realise you need to lift the whole engine up 10mm to fit it!

So suggest you also check your TMC40 against the PRM80. including that the ratio is the same!

Mike

 

[Tranona]

Not sure there is any real difference in performance. Beta and Nanni offer either on their engines. Minor differences in reduction ratios and the PRM is quite a bit longer and the output flange is lower (therefore engine sits higher). Both might be an issue if space is tight.

Why not ask Beta why they offer a choice and what the pros and cons are.

Gearboxes of this type are (in general) so reliable that it is unlikely that many users will be able to say much more than their gearboxes work!

BTW my Nanni has a TMC, but has not run long enough for any problems to show - not that I expect any.

 

[alahol2]

My TMC has got 500hrs without problem, but I wouldn't expect otherwise.

 

[steveallan]

TMC40

2000 hrs no problems

 

[charles_reed]

Both excellent boxes, but the TMC is more compact.

 

[sailorman]

Both excellent boxes, but the TMC is more compact.

i am told the PRM is fitted to inland charter boats as they will take "some stick"

 

[little shack]

Funny I have to replace a hurth 50 on my boat.May go the way of the prm if I can get one in easy enough 40 mm longer and 10mm higher output.if I have the room to move the shaft back 40mm and there is still room as not to foul the rudder are there any other problems with just moving the shaft back.

 

[sailorman]

Funny I have to replace a hurth 50 on my boat.May go the way of the prm if I can get one in easy enough 40 mm longer and 10mm higher output.if I have the room to move the shaft back 40mm and there is still room as not to foul the rudder are there any other problems with just moving the shaft back.

dont forget the PRM is hydraulic so a folding / feathering or a freewheeling prop + a brake

 

[Paragon]

dont forget the PRM is hydraulic so a folding / feathering or a freewheeling prop + a brake

Hi Sailorman, can you elaborate on this please, the implications of a hydraulic box on a folding/feathering prop is what particularly interests me?

From what's been said so far, it would seem that both are good boxes and if you can get the right ratio then either one is satisfactory!

Many thanks

John

 

[sailorman]

Hi Sailorman, can you elaborate on this please, the implications of a hydraulic box on a folding/feathering prop is what particularly interests me?

From what's been said so far, it would seem that both are good boxes and if you can get the right ratio then either one is satisfactory!

Many thanks

John

No problem for a MoBo
A sail boat with a mechanical box can lock-off the shaft via the gearbox but with a hydraulic box the fixed prop will freewheel.
i changed engines some 11 yrs ago but kept the MaxProp, i had to coarsen the prop pitch to get down to the rated 3000 Rpm

 

[Paragon]

No problem for a MoBo
A sail boat with a mechanical box can lock-off the shaft via the gearbox but with a hydraulic box the fixed prop will freewheel.
i changed engines some 11 yrs ago but kept the MaxProp, i had to coarsen the prop pitch to get down to the rated 3000 Rpm

Ah I see, yes understood, I thought the PRM80 was mechanical! Thanks for letting me know.

 

[SAMYL]

The only thing hydraulic about a PRM box is the gear change, it is not an hydraulic drive.

 

[sailorman]

The only thing hydraulic about a PRM box is the gear change, it is not an hydraulic drive.

Ah i stand corrected
i have the PRM 150
PRM150
FULL HYDRAULIC OPERATION LIGHTWEIGHT, COMPACT & RUGGED
i didnt realise the 80 was any different

 

[SAMYL]

To be fair Sailorman, when I think about it you are probably right.
If the engine is not running then it would be impossible to put the gearbox into gear as the pump will not be pumping to activate the gear change, so a folding prop or prop brake may be the answer.
You could try stopping the engine in gear but that may not work either - but it could be interesting when you start up again! Some gearboxes are permantly in gear unless the engine is running to activate the hydraulics - not PRMs as far as I know.
Some PRMs have a "get you home" facility if the hydraulics fail, but you have to dismantle the top cover to screw in a bolt to lock the drive.