01-03-2012, 05:07 PM
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Sand Trout
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Join Date: Mar 2010
Location: houston
Posts: 11
Cash: 707
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Quote:
Originally Posted by scott craft
Here's a good explanation from someone that's pretty good with this stuff:
Quote:
Originally Posted by 1995 US1
First, flatbottoms and marsh tunnels are two totally unrelated animals. I have an 1844 AlWeld Tunnel. The transom is 20" tall from the flat bottom to the top of the transom. My motor is mounted 1 1/2" above the top of the transom, for a total motor height of 21 !/2'. My motoor is a short shaft, 15" shaft.
Now the reason why a jackplate is nearly useless on a tunnel. The tunnel is shaped in a way to funnel water to the prop right at the back of the transom. The minute the water in the tunnel under the hull clears the transom, it goes to the sides, down, up, all directions. Because the area behind the transom is a low pressure area, compared to the boat bottom or the tunnel, there is nothing to direct a water flow to the prop. The further behind the transom you move, the more the water is spread out. Think of the tunnel as a water hose, the further from the nozzle, the more spread out the stream becomes. If you keep the prop right behind the tunnel exit, that is the area of least dispersment, the prop bites better. With my motor sitting 21 1/2" above the bottom of the boat, the hull can hit something and the motor never touches it. Why go any higher or further back? Hope this makes sense.
D
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a good after market cavitation plate and the right prop can solve this problem.
http://www.boatrightmarine.com/cuerp...ies&modelid=55
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