# Proper cav plate height on tunnel hull?



## Brett (Jul 16, 2008)

Depends on the type of propeller.
A factory prop won't have enough cup to function properly
in the top 2 inches of highly aerated water coming out the tunnel.
That means you have to be about 2 inches below the top to maintain bite.
A cupped prop lets you run with the anti-ventilation plate level with
or just slightly above the top of the tunnel, depending on running angle.

how I learned...

Pocket Tunnel


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## Dillusion (May 21, 2012)

So what I got from that is it should technically be aligned with the top of the tunnel plane, but also be 1" below the water line at rest and on a 4-6 degree angle from the bottom of whatever plane you are using whether it be the hull or the tunnel.

Where would be a good spot to start the tuning at if I have a jack plate? Bottom of the hull and raise it from there?


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## Brett (Jul 16, 2008)

With a jack plate, and the hull level, I'd start 1 inch below the top of the tunnel for testing.
Take a run at WOT, if no blowout occurs during turns, go up 1/2 inch.
repeat until blowout occurs, drop down a hair and you ought to be good.


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## el9surf (Dec 23, 2008)

My cavitation plate is mounted flush with the top of the tunnel on my shadow cast. The only thing I can't do with the stock prop is turn quickly while going fast.


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## Capnredfish (Feb 1, 2012)

You can also run higher by learning to drive one. You can back off throttle a little then turn wheel and apply more throttle again avoiding blow out running motor really high. Might not help in an emergency maneuver though as you could normally anticipate a turn and do the above method. How do I know? I owned a pos tunnel in the past.


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