Propeller Query - LH and RH

C

Charlie P

New Member
Joined
20 Aug 2018
Messages
12
Visit site
Looking to buy a folding propeller - hesitating at the severe price tags! Some advice from more-technical fellow travelers please.
I can buy a second hand Gori 18 X 15 LH for a good price. Recommendations from Brunton New are 2 Blade Varifold VF -70 - 17” x 15” OR 3 Blade Varifold VF -108 - 17” x 14”, RH - alternatively Flexifold 3-blade 18X13-3R. The engine is a Beta 43 and the boat a Jeanneau SO 40.
My query is whether the engine is equally happy running in 'reverse' (to drive a LH propeller) or whether such an arrangement will cause future 'gnashing of teeth' and howls of regret.
Appreciate all comments
 
Charlie P said:
My query is whether the engine is equally happy running in 'reverse'
Click to expand...
The engine always spins in the same way, it all depends on the gearbox.
You should check in its specs if it's rated for the same torque in fwd and reverse.
Many are, but not all.
 
Cantata said:
Simple answer is that with your setup you need a RH propeller.
Click to expand...

Not necessarily; some of the gearboxes fitted to the Beta 43 are quite happy to run in either direction, with no constraints. But others have different ratios and different power ratings in the ahead/astern settings. As MapisM said, the OP needs to check very carefully the spec of the gearbox on his engine.
 
I replaced my fixed prop with a Brunton two blade Varifold this summer. The lack of prop rotation at >5 knots and the accompanying whirring sound is priceless.

We tested the difference between the fixed prop locked in reverse, against the engine manufactures recommendations, and free. The speed difference was 1/2 a knot!

With the hull coppercoated and a folding prop the boat just slips though the water, hull speed is easily reached.

How often do you drive the boat in reverse?
 
Sandy said:
I replaced my fixed prop with a Brunton two blade Varifold this summer. The lack of prop rotation at >5 knots and the accompanying whirring sound is priceless.

We tested the difference between the fixed prop locked in reverse, against the engine manufactures recommendations, and free. The speed difference was 1/2 a knot!

With the hull coppercoated and a folding prop the boat just slips though the water, hull speed is easily reached.

How often do you drive the boat in reverse?
Click to expand...
I concur! Fixed prop is a personal 'pet hate'!
 
MapisM said:
The engine always spins in the same way, it all depends on the gearbox.
You should check in its specs if it's rated for the same torque in fwd and reverse.
Many are, but not all.
Click to expand...
Gearbox is PRM 150 D2 - sounds like Beta UK might be able to give me some insight
 
It appears to me that the PRM 150 D2 gearbox can be run to give either rotation. At the bottom of page 16 of the user manual (link below), in talking about twin engined installations it says 'It is therefore desirable that "handed" (i.e. counter-rotating) propellors be fitted. For this reason PRM gearboxes are capable of providing either hand of output rotation with any of the available gear ratios.'
https://www.prm-newage.com/media/uploads/5050834c6f7e0.pdf

(Note you will need to know the gear ratio of your particular gearbox in order to select the appropriate sized propellor.)
 
Just one thing...(Columbo chews cigar thoughtfully)...it may be that the PRM box, although happy to run either way, will in ‘get you home’ mode when the oil pump has failed, only run in reverse.
 
fisherman said:
Just one thing...(Columbo chews cigar thoughtfully)...it may be that the PRM box, although happy to run either way, will in ‘get you home’ mode when the oil pump has failed, only run in reverse.
Click to expand...

I think that, if the oil pump fails, there'll be no drive in either direction.
 
usually with a PRM you can take the lid off and there are allen screws to fix the clutch plates together, giving you drive in one direction only, and no option for neutral. I know someone who came home from off the Lizard to Helford in astern all the way, with an occasional 360 deg turn. Picking up the mooring was interesting.
 
fisherman said:
usually with a PRM you can take the lid off and there are allen screws to fix the clutch plates together, giving you drive in one direction only, and no option for neutral. I know someone who came home from off the Lizard to Helford in astern all the way, with an occasional 360 deg turn. Picking up the mooring was interesting.
Click to expand...

I bet mooring was more than interesting! The PRM emergency operation allows RH drive only, and as you say there's no neutral. There's also a limit of a third of max throttle when running in emergency mode.
 
Charlie P said:
Looking to buy a folding propeller - hesitating at the severe price tags! Some advice from more-technical fellow travelers please.
I can buy a second hand Gori 18 X 15 LH for a good price. Recommendations from Brunton New are 2 Blade Varifold VF -70 - 17” x 15” OR 3 Blade Varifold VF -108 - 17” x 14”, RH - alternatively Flexifold 3-blade 18X13-3R. The engine is a Beta 43 and the boat a Jeanneau SO 40.
My query is whether the engine is equally happy running in 'reverse' (to drive a LH propeller) or whether such an arrangement will cause future 'gnashing of teeth' and howls of regret.
Appreciate all comments
Click to expand...

I have taken off a RH Gori 16.5 by 13. 30 mm shaft. It was in perfect condition until moored at Figuera da Foz for a couple of months last year but electrical activity around the pontoon didn't do it or my port keel side any good. It may still be in good enough condition for you if you are not going too far. I took it off because I was going far and it was never the right prop for my boat and was even worse after an engine replacement.
 
Many thanks to all for your considered and thoughtful replies - especially 'Littlesister' who looked up the technical info and posted the link. I was in contact with Beta themselves today. They responded to the query 'Yes you can use a L/H prop. The gearbox is hydraulic so can work both ways. If you had a mechanical gearbox, you couldn’t do it.' So guess I am buying a LH folding prop.

I understand that it is not too tricky to adapt the throttle lever so 'ahead' will still be 'ahead' and vice versa.
 
Yup, all you needed to have is a confirmation that the g/box can handle full power/torque in both direction.
Reversing the throttle, depending on the specific lever, can be easy peasy or a bit more tricky, but feasible anyway.
It's the explanation (yes because hydraulic/not if mechanic) that doesn't sound convincing - at least as a general reasoning.
But maybe that's true for their own products, no idea.
If you are sure that you can trust whoever told you that, you're good to go!
 
Charlie P said:
Many thanks to all for your considered and thoughtful replies - especially 'Littlesister' who looked up the technical info and posted the link. I was in contact with Beta themselves today. They responded to the query 'Yes you can use a L/H prop. The gearbox is hydraulic so can work both ways. If you had a mechanical gearbox, you couldn’t do it.' So guess I am buying a LH folding prop.

I understand that it is not too tricky to adapt the throttle lever so 'ahead' will still be 'ahead' and vice versa.
Click to expand...

That's interesting, must be specific to that gearbox. I am buying a new propellor and my Borg Warner Velvet Drive which is hydraulic, apparently is purchased either for a LH or RH drive, it can't be changed. This is according to TS Noris because in my query he asked my to verify the gearbox number which has a code for LH and RH; this despite taking off a RH propellor. Anyway, I guess it's all part of making sure what they quote, supply is correct.

As a by the way, if anyone is checking this thread in future, I also discovered that for this gear box, Bruntons Autoprop requires a shaft lock for the propellor to adopt the zero pitch angle. It all adds up!
 
You must log in or register to reply here.

Share this page

Top