contra rotating outboard

beerbelly · 08 May 2016, 00:59

I'm currently in the process of buying a osprey eagle with a Yamaha 130 v4 2 stroke everything on the outboard seems good but its a contra rotating unit .I was under the impression that was only used if 2 outboards were in use one would spin the other way to eliminate any pulling to one side .will I have any problems using a contra rotating unit on its own

willk · 08 May 2016, 01:11

Shouldn't be a problem - so long as you never fit a normal rotation prop on it! (as someone on here did)

Pikey Dave · 08 May 2016, 09:59

Quote:

Originally Posted by beerbelly

I'm currently in the process of buying a osprey eagle with a Yamaha 130 v4 2 stroke everything on the outboard seems good but its a contra rotating unit .I was under the impression that was only used if 2 outboards were in use one would spin the other way to eliminate any pulling to one side .will I have any problems using a contra rotating unit on its own

As willk say shouldn't be an issue BUT If the boat was originally rigged for a standard rotation engine, the engine may have been offset on the transom to compensate for the prop torque. If it's had a left hander fitted since, you might have issues with it pulling over to the starboard side, take it for a test run first.

Chris · 08 May 2016, 10:41

Which side is the elephants trunk on, that should tell you if it was originally built for a std rotation.

If the trunk is on the Starboard side when you look from the back of the boat then it would have original been a std rotation engine fitted.

If this is the case you might need to be careful as the trunk could get caught in the prop if its long enough.

beerbelly · 08 May 2016, 13:47

thanks it has two trunks but my sr4 has a standard rotation outboard and the trunk is on the port side and never had a problem with it getting in the way .as for offset yes the guy who is selling it said it had been offset to counteract prop torque

Chris · 08 May 2016, 19:44

Quote:

Originally Posted by beerbelly

the guy who is selling it said it had been offset to counteract prop torque

check the engine is offset to Port (ie its about 20-30mm further to the left hand side of the transom when looked at from behind.) If so this is correct.

If not then its not the end of the world as the engine can be moved. Just needs to be done properly with the transom holes being doweled and filled etc.

beerbelly · 08 May 2016, 19:59

thanks I will take a tape and check it

jyasaki · 09 May 2016, 03:36

Props may be harder to come by. Selection for LH props can be limited.

jky

Pikey Dave · 09 May 2016, 15:44

Quote:

Originally Posted by jyasaki

Props may be harder to come by. Selection for LH props can be limited.

jky

+1 also LH props tend to come in larger pitches as contra rotating engines are usually rigged as twins

Sh1t happens

Stuart1975 · 09 May 2016, 16:23

Quote:

Originally Posted by Chris

Which side is the elephants trunk on, that should tell you if it was originally built for a std rotation.

If the trunk is on the Starboard side when you look from the back of the boat then it would have original been a std rotation engine fitted.

If this is the case you might need to be careful as the trunk could get caught in the prop if its long enough.

Don't get that at all. what does it matter what side trunk is as to what gearbox is fitted and it getting caught in prop . Can you explain more please

martini · 09 May 2016, 17:46

Left hand gearboxes have a habit of going bang much sooner than RH boxes. Something to do with the load on thrust bearings etc.

beerbelly · 10 May 2016, 06:40

Quote:

Originally Posted by martini

Left hand gearboxes have a habit of going bang much sooner than RH boxes. Something to do with the load on thrust bearings etc.

oh crikey I'm wondering if I'm doing the right thing buying this now

Poly · 10 May 2016, 08:04

Quote:

Originally Posted by martini

Left hand gearboxes have a habit of going bang much sooner than RH boxes. Something to do with the load on thrust bearings etc.

Is that all LH boxes, or just some particular brands/models?

Chris · 10 May 2016, 10:02

Quote:

Originally Posted by beerbelly

oh crikey I'm wondering if I'm doing the right thing buying this now

I would not be put off if its all in good working order.

beamishken · 10 May 2016, 12:43

Isn't there the danger of any older gearbox going bang? If it does then a good opportunity to fit a rh rotation box as a replacement
Presumably the rig is a little cheaper (or its a good bargaining chip) because it's got a l/h engine fitted
It wouldn't put me off if everything else checked out OK

9D280 · 10 May 2016, 13:23

Quote:

Originally Posted by Chris

If this is the case you might need to be careful as the trunk could get caught in the prop if its long enough.

That's not a trunk - it's a hose!

If you have a long shaft engine and the trunks are towards the edges of the transom you shouldnlt have an issue.

My new trunks when I got them were so long that they stuck above the trasom by about 3". (76.2mm for those of you who think metric) wghen folded. They would have fouled my prop spectacularly, but they only need to be long enough to get above the waterline at rest (+ a couple of inches / few CM for dealing with waves) to function properly- so I cut mine level with the top of the cut-out for the engine - if the water gets higher than that it has a much easier route into the boat anyway!