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K. Kergan
K. Kergan, Marine Mechanic
Category: Boat
Satisfied Customers: 1030
Experience:  24 yrs exp. Inboard/Outboard mechanic Mercury/ Mercruiser, Volvo Penta and OMC, Johnson/Evin.
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I have a 4JH3TE Yanmar Engine and fitted gearbox KBW 21 clutch

Customer Question

I have a 4JH3TE Yanmar Engine and fitted gearbox KBW 21 clutch in a 34Ft cruiser I purchased this boat as is. I am not too sure this is the gearbox that should be fitted
I sure would like your advice on this gearbox and suggestions you may have to a replacement that would fit the engine and where would I find the proper box

Kind Regards.
Frank Finegan.
Submitted: 4 years ago.
Category: Boat
Expert:  Michelle-mod replied 4 years ago.


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Customer: replied 4 years ago.
I am not sure what information you are looking for, I did not receive any answer to my query.
Regards


Expert:  Walt-mod replied 4 years ago.
Thank you for your patience, your business is very important to us, we are waiting on the Professional with the right expertise to come online. Feel free to let us know if you would like us to continue searching for an Professional or if you would like us to close your question. Thank you for your understanding!
Customer: replied 4 years ago.
Yes I would like as much information as possible to my question,thanks
Regards.
Frank
Expert:  K. Kergan replied 4 years ago.

Hi, my name is Kerry

Yanmar offers three different transmissions with this engine, the KM4A is an angle drive with a cone clutch and the KBW20 and KBW21 are both straight drives with a multidisc clutch pack. The KBW21 is the more durable of the two.

Why do you think it's the wrong transmission for your application?

Customer: replied 4 years ago.
Hi.Kerry.
Thanks for getting back to me,my problem is i do not know the difference between the different boxes,The KBW21 box seems to be a crash box to explain the shaft needs to be stopped rotating before changing gear I think.Most other boats you can go from forward to reverse very quickly.
I am not sure I can do this with the KBW21,If not which box would be suitable.I have found out this engine and box were bought for a barge and the deal fell through, they were fitted to the cruiser then.The boat works fine other than trying to get it in to and out of gear.
Regards.
Frank Finegan.
Expert:  K. Kergan replied 4 years ago.

The KBW20 and KBW21 are identical except that the KBW21 has it's gears specially treated to be harder and more durable. The KBW21 is used on more powerful engines than the KBW20. Aside from the temper on the gears these two transmissions are virtually identical and are available in the same gear ratios.

The KM4A is a transmission with a cone clutch which may be more to your liking but it would mean that the engine orientation would need to change because of the angle on the output flange.

I seems to me that the transmission you have now should be able to shift fwd/rev/fwd/rev just like any other marine gear.

K. Kergan, Marine Mechanic
Category: Boat
Satisfied Customers: 1030
Experience: 24 yrs exp. Inboard/Outboard mechanic Mercury/ Mercruiser, Volvo Penta and OMC, Johnson/Evin.
K. Kergan and other Boat Specialists are ready to help you
Customer: replied 4 years ago.
HI Kerry.
Thanks for your reply It gives me peace of mind now.

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