13' Engine Mounting Height Recommendation - 25hp

[number9]

I'm selling my 25hp 4-stoke Yamaha long shaft to a friend with an older 13' with a 15" transom. His Whaler already has a two piece lift bracket installed similar to the one linked below.
http://continuouswave.com/whaler/cetacea/cetaceaPage56.html



Engine is tiller steer and has the clamp on bracket so once mounted any height adjustment will take more effort than normal hole up or down. A transom thick piece of two-by or plywood will be bolted to the forward side of the lift bracket for clamping engine and to attain final mounting height. Do you have an estimate for how far above hull bottom the cavitation plate should be for best performance. I also noticed the drain is rather close to bottom, about where should a 13's drain normally be in relationship to surface of the water when a well balanced boat is at rest. If anybody has same boat/motor combination and has a prop recommendation that would also be appreciated.

Thanks in advance for the advice you may offer.
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[jimh]

A 13-footer with the notched transom cut for 15-inch-shaft engines has a very deep engine splash well with the drain just about at the bottom. Boats with that deep engine splash well will have the drain submerged all the time. As a result, if the drain is left open, the splash well always has some water in it.

The later 13-foot hulls changed to a sink-style, narrower, and much shallower splash well, and they had a straight transom for 20-inch-shaft engines. Many Boston Whaler boats have these shallow splash wells, and the drains of those splash wells usually should remain above the waterline or just at the waterline, as the splash well is not intended to always have water in it, or, if some water remains in the splash well, it won't be very deep.

Since the notched transom is designed for 15-inch-shaft engines, if a 20-inch-shaft engine is used, it should be mounted at least five inches above the transom using some sort of bracket or jack plate.

[macfam]

On our 1987 13' Super Sport with a 30 E-TEC the anti-ventilation plate was about 1 - 1.5 inches above the bottom of the boat.
That seemed to be a sweet spot for best performance on our rig.

[number9]

jimh,
Thanks for the good info on the deep splash well and explaining that/why the drain will be under water. The photo you added does show the type of lift bracket. A wooden pad will be added to the lift bracket(s) to hang and clamp the motor. The pad will be on the forward face of the lift bracket(s), span the width and will extend from the top of transom to high enough above the lift bracket(s) to get the desired height.

macfam,
Thanks for your sweet spot info. Sure yours is much sweeter than this 60s beater will ever be.
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