Foot/Prop Spray

[kt4vq]

I have an issue....or at least I think it is a problem.<br /><br />I have a 16.5' fish and ski with a 70 hp outboard. I have a hydofoil on the foot but the spray was there before I installed the hydrofoil. The hydor foil brings me onto plane very quickly.<br /><br />When I am running at 15-20 mph and up I have a "V" shaped spray that comes up from the foot and extend to the ski 3-4' high depending on the speed. The faster the higher it will go. <br /><br />I can trim the motor to what I feel is up too high and reduce this spray but the trim is so high the boat will porpoise or cavitate.<br /><br />What causes this and any ideas how to solve it?<br /><br />Thanks gang.

 

[Solittle]

Re: Foot/Prop Spray

Where is the cavitation plate relative to the bottom of the hull?

 

[LubeDude]

Re: Foot/Prop Spray

My bet is that the engine is at least 1 if not 2"s too low.

 

[timbo1963]

Re: Foot/Prop Spray

Hey Don, How's Davey.<br /><br /><br />ku4fk

 

[kt4vq]

Re: Foot/Prop Spray

Hi Tim, seems you found my web site...<br /><br />I assume the the cavitation plate is one of the two horizontal plates just above the prop.<br /><br />The top plate is flush with the bottom of the hull. The bottom plate is 1 1/2 to 2 inches below the bottom of the hull.<br /><br />Sorry I am such a rookie and don't which plate you are asking about but I do appreciate all of the help for you seasoned folks.<br /><br />TIM WENT TO MY WEB SITE AND SAW MY HIGH TECH DOG FEEDER. http://kt4vq.com too funny Tim.

 

[LubeDude]

Re: Foot/Prop Spray

Originally posted by kt4vq:<br />[QB] Hi Tim, seems you found my web site...<br /><br />The bottom plate is 1 1/2 to 2 inches below the bottom of the hull.<br />

Yep, Engine too low. Raise it 2".

 

[walleyehed]

Re: Foot/Prop Spray

depending on how it performs after raising up (2 holes would be 1.5") you may need to go 3 holes if it doesn't ventilate badly. I would try one hole at a time, but LubeDude is right, I believe it needs to come up quite a bit.

 

[LubeDude]

Re: Foot/Prop Spray

Isnt it amazing how many boats have the engine mounted too low from the dealer!! And I mean WAY too low.

 

[timbo1963]

Re: Foot/Prop Spray

Don, I'm a little worried about Davey. He don't move much...is he stiff?? Maybe that high tech feeder didn't feed him.

 

[kt4vq]

Re: Foot/Prop Spray

He is bored (stiff as a board).....when I get back from fishing he comes out to say hello!

 

[kt4vq]

Re: Foot/Prop Spray

So .... should I have the bottom plate flush with the bottom of the hull?

 

[BillP]

Re: Foot/Prop Spray

Or 1/2" above the boat bottom...just enough to clear the water when running fast. Otherwise it makes drag. The fin needs to be above the bottom too. That's a little tricky if you have a deep vee hull with flat fin. That's where vee shaped fins work best.<br /><br />Another thought...If you are pulling skiers you want the motor as deep as you can run without dragging the caviation plate or fin. If just running for speed you can raise the engine up 1" or so above the boat bottom and only see cavitation in quick turns.