12 ft tunnel hull motor questions

[sunbeam2]

I have what I have been told is a Baja Scat Cat 12 ft tunnel hull speedboat<br />Where should the motor height be in relation to either the bottom of the hulls or the bottom of the tunnel. I am using a long shaft 12 hp johnson work horse that places the cavitation plate just below the lowest spot on the twin hulls and the motor surges or cavitates when it gets up on plane

 

[Dhadley]

Re: 12 ft tunnel hull motor questions

Those take a fairly specialized prop. Once mounted correctly -- or rather mounted in the most efficient position -- the AV plate will be even or above the top (roof) of the tunnel. <br /><br />What prop are you running?

 

[sunbeam2]

Re: 12 ft tunnel hull motor questions

The prop is alum 8.5 x 9 cupped and I just installed a stingray foil on the motor. I have not yet tried out this combo, too cold and windy.<br /><br />what do you mean by AV plate????

 

[Dhadley]

Re: 12 ft tunnel hull motor questions

The anti-ventilation plate is the flat plate right above the prop. Commonly called the cavitation plate.<br /><br />If it's even with or below the sponsons, be very careful with the fin. They are designed to run on top of the water. If they run below the surface they can do some really wierd things.

 

[sunbeam2]

Re: 12 ft tunnel hull motor questions

If I post a picture of the rear on the tunnel hull can someone tell me if the engine is right or wrong??? I will also have to have a tip on how to post a pic here