Left or right handed propeller?

[mauroc]

I need a new prop for my 2008 Beneteau 43'.

The official Beneteau online catalog (see screenshot) specifies a right-hand propeller for that year/model, while the one actually installed on the boat is left-handed (see attached photo. BTW - I also checked the actual shaft rotation: clockwise viewed from stern when in reverse gear).

The Yanmar 4JH4AE engine manual and the KM35P transmission datasheet also state that the prop should be right handed. My local Beneteau distributor cannot explain the discrepancy either.

Before I go ahead and order a 19x13 left-handed prop and shell out $800-$1000 (assuming there is one available), I was wondering if anyone can help explain the mystery. Could it be a specific production run for the Yanmar engine with a different rotation than reported officially? Thank you

 

[jssailem]

That is definitely a LH prop. No knowledge as to why.
Here is an image of my RH prop for comparison.

 

[Michael Davis]

Yanmar engine with a different rotation

Which way does the crank rotate from the pulley end. It's relatively easy (not cheap) to change the direction of rotation if you have a good reason. Note all the sport fishers with counter rotating props. Some transmissions change rotation as well.

 

[Jackdaw]

Do you actually have a Yanmar, or is it a VP? If it's Volvo then likely a LH turner.

 

[Michael Davis]

If it's Volvo then likely a LH turner.

So true! Ran into that problem changing a Volvo to Yanmar in a Westsail 32.

 

[mauroc]

Do you actually have a Yanmar, or is it a VP? If it's Volvo then likely a LH turner.

yes, it's a Yanmar 4JH4E

 

[mauroc]

Which way does the crank rotate from the pulley end. It's relatively easy (not cheap) to change the direction of rotation if you have a good reason. Note all the sport fishers with counter rotating props. Some transmissions change rotation as well.

not sure which way it rotates from the pulley's end. I am not at the boat now but will check. Your message suggests that the previous owner could have tweaked the transmission to change the rotation. I wasn't aware it can be done so easily.

 

[Michael Davis]

Is the shift linkage set up correctly? Not so easy to change trans. but some are made to do that. Changing the engine is pretty easy (timing, cam shaft, starter etc.) but I would want a good reason to spent the money.

 

[Gunni]

Looks like the Kanzaki KM35P outputs RH.
https://www.yanmar.com/media/global...pulsion/operationmanualgears/outlineKM35P.pdf

 

[Jackdaw]

Which way do you push the throttle handle to move forward????

 

[mauroc]

Looks like the Kanzaki KM35P outputs RH.
https://www.yanmar.com/media/global...pulsion/operationmanualgears/outlineKM35P.pdf

yes - correct. It's supposed to be RH at the output (in forward) and LH (or counterclockwise looking forward) at the input. I assume the input to the gearbox is the crankshaft itself, without intervening gears, but I have not checked the drawings yet.

I am away from the boat but have asked someone to go and look which way the engine crankshaft turns. That will reveal whether the engine itself was modified to turn the opposite direction, or the gearbox was. Or perhaps - as Michael hints at - the cabling was set up improperly (I think it's unlikely, but it's a terrifying thought that I would have been going in 'reverse' for the last two years -that's how long I have owned the boat. The specs show that the reverse ratio is 3.16 vs 2.61 in forward. That would have made me 20% slower? Also, why would someone install a LH prop just because the cabling was done incorrectly? The whole thing remains a mystery).

 

[mauroc]

Which way do you push the throttle handle to move forward????

forward

 

[mauroc]

PS - I heard back from the boat's caretaker in Puerto Vallarta and the input to the gearbox rotates counterclockwise looking forward (or the crank at the pulley's end rotates clockwise looking aft), as it should based on the engine and gearbox specs. In theory, that would mean that the prop should be RH, but it's not.

I suppose this leaves me with either 1) the gearbox has been modified or 2) the cabling to the gearbox isn't set up properly, so I am actually in reverse when I should be in forward. Either way, that leaves me with more questions that answers, and the plot thickens....I guess I will have to have someone check the cabling as a next step. Any other idea?

 

[Michael Davis]

?????? keep us posted.

 

[JimInPB]

My best guess, is that a previous owner lost or ruined the original prop, then found your existing prop cheap & reversed the shift linkage to make it work.

But, that is very much just a guess.

 

[mauroc]

My best guess, is that a previous owner lost or ruined the original prop, then found your existing prop cheap & reversed the shift linkage to make it work.

definitely quite possible. I am having someone look at the linkage and will report back when I hear back. Thanks everyone for the feedback so far.

 

[LeslieTroyer]

Could be a repower from a VP, and running in reverse so didn’t have to buy a new prop

 

[Michael Davis]

good point about the prop being cheaper.

...but it's a case of penny wise, pound foolish. The efficiency of the prop in reverse and the different gear ratio would put fuel cost greater than your savings.

 

[mauroc]

well, it turns out the cabling is in fact installed incorrectly and the transmission has been functioning in reverse with the throttle in the forward position the whole time I have owned the boat (2+ years). I have no idea why this was done by the previous owner (only one owner prior to me). Both of the hypotheses mentioned by a couple of you are valid (a LH prop bought on the cheap, a repower from a Volvo engine), but perhaps it was another reason. Who knows .

All I know is that the 500+ hours I have put on the engine since purchasing the boat two years ago, the transmission was rotating in the opposite direction from the one it was designed for. I have no idea if this may have caused unusual wear and tear on the transmission itself. Certainly, the loss of speed has caused some frustration on my part (the boat has always felt a little slow under engine, but I suspected an improperly sized prop), and perhaps higher fuel costs.

Thanks to those of you who have contributed their own thoughts. Very helpful.

 

[jssailem]

Wow, what a discovery. This will make a whole world of difference in your boating experience.