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Laker 14 Tunnel Boat Plans
Page Thirteen

A word about motor height.

On a typical fishing boat, the motor's cavitation plate is about even with the bottom of the boat, or up to an inch below the bottom.

Motors on racing boats are mounted much higher.

On a tunnelboat you can generally jack your motor up as high as performance dictates, to the point where the entire "bullet" is actually above the deepest part of the boat. There will still be plenty of spray coming through the tunnel to feed the cooling water intake, and you will have reduced engine drag to the barest minimum.

In order to take full advantage of this sort of engine setup on your tunnelboat, you will surely need hydraulic trim. Without the ability to trim your engine down, pushing your prop deeper into the water, and directing thrust downward somewhat, you may have a very difficult time getting your boat on plane.

Furthermore, I would go so far as to say that trim on a boat of this type and size is pretty much a requirement -- not only to get the most out of the boat, but also FOR YOUR OWN SAFETY. In a tunnelboat that approaches or exceeds 60 mph, blowover is a real possibility. An engine trim angle that works well going downwind may be downright dangerous going upwind. Or, a trim angle that's best for upwind, will likely be disappointing (though not dangerous) when you head back downwind.

Buy a motor with trim, or rig a "homebuilt" system: see HERE for some ideas.

Trim switches are mounted on the wheel, readily accessable to the driver's thumb.

Also in the picture, the emergency kill-switch mounted on the dashboard. These are required for racing, and a good idea for the non-racer as well.

I feel the only real option for a tunnel boat is a foot-operated throttle. With your engine jacked really high , your prop is half out of water and will want to "paddle-wheel" or "walk" to starboard, thus pulling your motor into a right turn. You will want two hands on the wheel to resist this torque -- and to keep a thumb on the trim switches, and just to control your boat generally.

The "Hot Foot" from T-H Marine is the standard item, but there are other brands, like the "Hot Shot" from Bob's Machine Shop. I once had one called "Lead Foot." These units use the standard throttle cables recommended for your engine.

Bolt the throttle through the tunnel battens and floor, or glue a lumber or plywood base to the battens and attach the throttle to that. The throttle shown is mounted on an optional slide plate which gives it a few inches of fore-and-aft adjustment.

A jackplate is a handy device for dialing in that perfect engine height. One can be purchased, or you can build a simple one yourself.

Please consider my Jackplate Plans.

You can use the shifter manufactured for your motor, or simply make one.

Racers: Rules for pure stock classes state that the driver must be able to shift the motor while sitting in the seat and with one hand on the steering wheel.

You will need a seat for your boat.

Here's one you can build in an afternoon, probably with plywood leftover from your boatbuilding project.

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