L/H and R/H props

[Gordon]

Having changed from Volvo to Beta engine I need to change to right hand prop.
Why isn't it possible to just use reverse to go forward
and keep the left hand prop?

 

[sailorman]

gearing different in astern + wear on bearings

had you fitted a PRM box they will run either way & more reliable than a mechanical box

 

[Eygthene]

My old boat had a Petter mini six which had a prop of the wrong hand, so it was in reverse gear when motoring forward and vice versa. The gearbox had the same ratio in forward and reverse, so no problem there. The engine eventually wore out after 25 years, but the gearbox was still going strong - no problems. The cables to the remote lever were simply swapped over.

 

[Latestarter1]

Sailorman,

You need to understand what Gordon is saying. Sounds like he is fitting a little puddlejumper engine for which only only mechanical gerboxes are available. Beta offer option of PRM or TMC mechanical boxes as standard options, and it sounds like he has a PRM, which is a nicer box.

Most small boxes built to operate with standard rotation engines i.e. providing a clockwise rotation of the gearbox input shaft when viewed on input. In forward drive the output shaft rotates opposite to input shaft therefore requiring a right hand propeller.

Some small mechanical boxes from ZF and TMC can be made to turn in A/S direction but require a cooler, by the time you have done that simpler to fit new prop.

With a few Velvet Drive exeptions pretty much all modern hydraulic boxes offer A/S rotation PRM, ZF, Twin Disc. However not relavant to this discussion.

 

[sailorman]

[Sounds like he is fitting a little puddlejumper engine for which only only mechanical gerboxes are available. Beta offer option of PRM or TMC mechanical boxes as standard options, and it sounds like he has a PRM, which is a nicer box .]


WOTS your point then /forums/images/graemlins/confused.gif

PRM boxs can in either direction. i have a PRM 150 /forums/images/graemlins/ooo.gif

 

[Gordon]

So that's the difference between TMC and PRM

I am getting TMC which is a bit cheaper than the PRM
so I better get a new r/h prop.

Probably more expensive than using PRM and sticking with
l/h prop but I don't like the idea of running in reverse to go forward all the time no matter which gear box.

thank you for anwers

 

[Graham_Wright]

Ask Beta;- they're very friendly.

 

[Kurrawong_Kid]

I had this problem when I replaced an MD2B with L/H propellor with a Beta engine. No room for hydraulic gearbox, but chat with MD of Beta very helpful. Compact 40hp capability TMC gearbox for 28hp. engine with fresh water cooling fitted and is run in reverse. Now done in excess of 1100 hours with no problem although I did change the transmission oil at half the recommended hours. The gearbox runs indirectly but this is no different from many car gearboxes in all but one of the higher gears! The designers of the boat (Holman and Pye) advised not to change to a R/H propellor because they said it would make the boat even more impossible to steer astern (offset propellor)!

 

[Gordon]

Now you have got me thinking......should I go for PRM
and keep my original prop??

 

[sailorman]

hydraulic boxes are fitted to many hire boats 4 a reason.
the PRM can be "Crashed" from ahead to astern ( i am told) without damage.
if you fit one the only down side is that the prop will rotate when sailing.
i have a MaxProp so this situation doesnt arise

 

[Latestarter1]

Gawed people can be hard work.

Smallest hydraulic PRM box is the 150 which is almost as heavy as the the little Kubota engine and takes around 100 Hp. We are talking puddlejumper stuff here. Not appropriate.

Below the PRM 150 PRM model boxes are mechanical with no A/S choice. Small TMC Technodrive MECHANICAL boxes were junk compared with PRM MECHANICAL boxes.

TMC was purchased by Twin Disc Corp a few years ago a truly World Class manufacturer. I have since heard that they have become a much better. However I still prefer the PRM Vs TMC, PRM is British and you can be assured of getting tech support if needed.

I have been forced at times to adapt mechanical ZF's to run A/S always hated it and mechanical efficiency is worse thats why you need a cooler.

All for the sake of a new prop........

 

[sailorman]

Percy Riley Motors /forums/images/graemlins/wink.gif
the last of our real Motor Manufacturers