Who to talk to about a Yanmar KBW10 Transmission?

[Zach]

Hi,

I've got a 2.83:1 gearbox, and a small prop aperture turning a 16 inch prop with a 19 pitch. The aperture doesn't have any room to add any more diameter to the prop.

If I run her hard I get cavitation until the boat gets up to speed. This makes docking in current interesting as I have next to no thrust, and not much prop walk until the boat is moving.

I don't get very much thrust out of her into the current, as the prop cavitates at high RPM's. I can reach better than full RPM. I'd like to find a 2.14:1 transmission and see if I can drop the pitch back towards the recommended 16x9 for my 3JH2E engine.

Searching around, I haven't found much if any information about where folks go to have work done on these transmissions.

Thanks,

Zach

[a64pilot]

Is your prop "cupped"? On speed boats, cupping the prop is one way to lessen cavitation.

On edit, maybe a four blade prop? I'm assuming your already a three blade.

[Zach]

No cup. Right now it is a 2 blade prop.

[atoll]

Originally Posted by Zach

No cup. Right now it is a 2 blade prop.

changing to a 3 blade prop would go a long way to stopping cavitation.

link below to do the optimum prop size calculation

Vicprop - Propeller Calculator

[Zach]

Thanks for the link Atol,

They pretty well confirmed Yanmar's suggestions for my boat/horsepower.

18.7 x 10.2 with a 2.83 transmission. I've got a 16x19 2 blade that ain't cutting muster. Yanmar spec's an 19x12 prop for this engine/ transmission ratio.

VicProp confirms the 16x9 suggestion from Yanmar with this engine and a 2.14 transmission.

Flex-o-fold came back with a suggestion for a 17x14 3 blade folding, which I don't have enough room in the aperture for.

Pretty cool numbers to play with too. Thanks for sharing it!

Zach

[atoll]

Originally Posted by Zach

Thanks for the link Atol,

They pretty well confirmed Yanmar's suggestions for my boat/horsepower.

18.7 x 10.2 with a 2.83 transmission. I've got a 16x19 2 blade that ain't cutting muster. Yanmar spec's an 19x12 prop for this engine/ transmission ratio.

VicProp confirms the 16x9 suggestion from Yanmar with this engine and a 2.14 transmission.

Flex-o-fold came back with a suggestion for a 17x14 3 blade folding, which I don't have enough room in the aperture for.

Pretty cool numbers to play with too. Thanks for sharing it!

Zach

the kbw100 I think was originally made by zf/ hurth,and are pretty common,you night think about upgrading to a kbw 150 if replacing the gearbox to a different ratio as there are know issues with wear on the smaller model with higher torque,can buy them in the uk new for about £500 or second hand around the £150-200 mark,spline and coupling is the same,just beefier drive plates inside.

[LeaseOnLife]

Zach

in case you are looking for a 2.14 transmission, I am looking for a 2.62 or larger ratio transmission for my 4JH2-TE. I was able to fit a 3 blade 21" maxprop so I would favor a slower turning prop.

Warning: my trans has 5000h on it, with a rebuild (bearings and clutch packs) at 1600h. The rebuild was not because of failure but in prep for our long journey. Also, we had a failure of our stuffing box, and the paint is bubbling in spots, the trans really should be stripped and repainted. I was planning to do this this winter, but with the new 21" prop I am looking for a different ratio transmission.

Let me know if you are interested in swapping trannsmissions. I live in Michigan.

Dirk Lison
s/v Lison Life

[tdh1849]

There are 2 good sources in Ft.Lauderdale. #1, Complete Yacht Service, Yanmar dealer ask for Mark, tell him I told you to call,( formerly from there, 1st name is Pat).
2nd source is "Frank and Jimmys Prop Service", Mark has their #.

Both are top companies in Ft.Lauderdale..

[a64pilot]

I think you can "fix" it with a three blade prop with some cup to the blades.
But if there are known issues with the tranny? Once you get the prop to stop cavitating, the torque the transmission is under will go up. Now cavitation is limiting the torque

[NCboatrx]

Zach,

A 2 blade propeller in a tight aperture is very inefficient.
A 3 blade propeller will provide substantially better drive in forward and the potential for some reverse thrust and brakes.

Stanley

[Zach]

Thanks for the replies!

I've got a request into Cambell-sailer to see what they recommend for a prop, going with the idea that a cupped 3 blade prop might do the trick in the aperture.

I'll have to do some studying to see what other transmission models fit the same dimensions and bellhousing pattern of the 3JH2E, as it doesn't sound like finding a spare of this model makes sense if it has known weaknesses.

Thanks,

Zach