cavitation problem

[backhoebob]

i have a 1988 19' maxum openbow with a 150 hp blackmax that i put on this boat. the problem is that it is cavitating after i get on plane,the motor is mounted all the way down and trimmed all the way in.the cavitation plate is almost 4" above the bottom of the boat.this is a 25" shaft motor and i thought it would work on this boat,it runs great and i got a super good deal on this motor.i really do not want to get rid of it,any ideas on what i could do to help this problem maybe more pitch or a 4 blade prop or both maybe a setback plate would help.any advice would help,THANK YOU!!!!!

 

[WillyBWright]

Re: cavitation problem

Welcome to iboats. <br /><br />Sounds more like you have a longshaft 150 on an extra-long shaft boat. That plate has to be even or an inch or two up or down. 4" is way too much. A 4-blade won't help. I have seen High Five's run quite high, but I still think 4" is too much. With a jackplate, you can mount the motor lower. But the steering cable situation can get pretty interesting.

 

[Dhadley]

Re: cavitation problem

Welcome Bob!!<br /><br />I'd be inclined to try some props with a lot of bite rather than change anything right now. naturally a setback will help. Just look at your steering set up to see how far back you can go. <br /><br />For the moment let's look at what you have. What prop? Tell us all you can about it -- pitch, diameter, style, material etc. We assume it's a 3 blade.

 

[gatorred]

Re: cavitation problem

cut the transome down 4in's from top or put angle iron's and make the motor drop several in's down if you go with set back use a ss prop too it bit's water better

 

[Dunaruna]

Re: cavitation problem

O/k, I'll be the PITA that corrects the homework.<br /><br />It's a ventilation plate, not cavitation. your prop is ventilating, not cavitating.

 

[backhoebob]

Re: cavitation problem

it is a quick silver stainless steel 19 pitch 14.25 diameter 3 blade prop that is in perfect condition with no nicks or dings

 

[Dhadley]

Re: cavitation problem

OK, not a bad prop but it really doesn't like a lot of height. At least not any I've seen, but still a good prop. A 4 blade will definately help but be careful not to use a 13 3/4" one. Stick with the 14 1/4" diameter ones. Or more. Turbo just came out with some 15" stuff. <br /><br />What kind of hull do you have?<br /><br />Hang in there. We'll see what can be done without cutting the transom. We'll find something to try.<br /><br />Walleyehed, got any big diameter 19 stuff?

 

[Texasmark]

Re: cavitation problem

Ok Dun, It's not a ventilation plate it's an "ANTIcavitation plate"......and that terminology comes way back from the '50's. And if you'll notice, with the new engines run higher out of the water, with higher rake props, it's larger, for good reason; to prevent "blowout" er ah cavitation. Grin<br /><br />Mark

 

[backhoebob]

Re: cavitation problem

not to sure what you mean by what type hull i have all i know is it is a v hull and has a small v in the back not flat.the very bottom of the hull at the back also has a slight v to it.hope this helps.thanks!!!

 

[walleyehed]

Re: cavitation problem

Walleyehed, got any big diameter 19 stuff?

14-3/4X approx. 19 TXP.....

 

[backhoebob]

Re: cavitation problem

talked to a buddy of mine today he has 3 or 4 different size and pitch props that he is going to lend me.going to try a couple of them next week and will post results,also i tried to explain the type of hull i have the best i could but have'nt had any feed back,hopefully one of these props will help.