A Photo & Discussion Forum for Wharram Design Enthusiasts

Yamaha 9.9HT vs 15 image

Thought I would share a picture of a Yamaha 15 vs the 9.9 High Thrust showing size of prop.

There is always lots of talk about engines on a Wharram and I cannot recommend the 9.9 High Thrust on a T38 enough. So quiet people do not know they are on, 20 lt fuel lasts forever, reliable,very easy to service and for a small fee one can get electric trim tilt so motors are raised from cockpit. Effortless and pleasurable. Speed is good and constant even in chop due to large props. I understand the price is off putting, but have seen wharrams with two stokes, diesels etc and by the time they have been engineered to fit and maintained doubt the saving is that great. Even if you can live with the smell and noise

Whats not to like? (except the broom stick to hold the sled in reverse!)

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IMG_0337.jpg, 2 MB

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Permalink Reply by Robert on October 21, 2013 at 9:41am

Hi Jacques, unfortunately that would not work. The Yamaha 9.9 high thrust motors have a lower gear ratio to allow them to drive the larger props.

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Permalink Reply by Dan Hardwicke on October 21, 2013 at 9:46am

Hi Jacques,

These 9.9 Yamaha's are for ferrys,barges and relatively heavy non planning vessels. So have lots of torque and excellent holding power in astern. One would have to do some research on gearbox ratios as these have to be compatible to prop size and engine rpm. The Yamaha ratio is 2.92:1 I think but would have to check. Pull up the tech data sheets and have a look, I am sure it is possible.

Jacques said:

Would that be ok to put such propellers on regular 9.9 (i.e Tohatsu)?

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Permalink Reply by Dan Hardwicke on October 21, 2013 at 9:47am

Ok there you go - No. Thanks Robert!

Yamaha gear ratio 13:38 and tohatsu 13:27. so definitely not a straight swap.

Dan Hardwice said:

Hi Jacques,

These 9.9 Yamaha's are for ferrys,barges and relatively heavy non planning vessels. So have lots of torque and excellent holding power in astern. One would have to do some research on gearbox ratios as these have to be compatible to prop size and engine rpm. The Yamaha ratio is 2.92:1 I think but would have to check. Pull up the tech data sheets and have a look, I am sure it is possible.

Jacques said:

Would that be ok to put such propellers on regular 9.9 (i.e Tohatsu)?