Prop and anti cavitation plate question

[honald112]

I have a 1975 reinell t-1900 tri hull with same year 115 evinrude. At WOT she is at 5100 rpms and goes about 38 with just myself and some gear in the boat. I have a 13x19 OMC aluminum prop. I would like to get alittle more top end. Should I try a 21 pitch or just live with it. The motor is tuned well and all four cylinders have 122 psi of compression. It is well taken care of.

Second question: I have been reading up that the anti cavitation plate should be in line with the keel. Mine is about a half inch lower. I can just about see it out of the water when WOT. Would it make big difference moving it up that half inch? Thanks for any advice from the master of props!!!
-Jake

 

[honald112]

Re: Prop and anti cavitation plate question

Oh and just a side note; the boat comes out of the water after every use and I pressure wash the bottom of the hull and use spray on wax from the car wash. I try to keep my rig clean. Thanks again

 

[surrender]

Re: Prop and anti cavitation plate question

Others will have more info, but I would say start by raising the motor at least one hole and re testing. Find out the max rpm for that motor and shoot for that. I dont know if 5100 is right.

 

[honald112]

Re: Prop and anti cavitation plate question

My max range is 5000 to 5500. I'll be moving it up tonight. Any suggestions on an easy was to do it?

 

[steelespike]

Re: Prop and anti cavitation plate question

Never done it personally.But as I understand it you put a wooden block under the skeg raise the front of the boat so the skeg touches the block loosen the apropriate bolts leaving those that slide.Continue to carefully raise the bow till the motor moves up.Normally you would raise it a hole at a time to a point just before venting
(cavitation) becomes a problem. Sometimes this requires raising the mount itself.
A prop with some cup will help get the most height.You could gain 1 or 2 mph and a couple of hundred rpm under ideal conditions. After raising the motor select a prop based on your results.Would be good to get to at least 5,500 rpm.Going to a 21 will lower your rpm even more so a 17" pitch is probably what you will end up with,depending on your results after raising the motor.

 

[honald112]

Re: Prop and anti cavitation plate question

I pulled my motor up so the anti cavitation plate is in line with the keel. Got 40 mph out of her at 5700 rpms. Should I leave it or go to. 21 pitch now. Man. Says 5500 is max. Any advice?

 

[BaileysBoat]

Re: Prop and anti cavitation plate question

Sounds well set up for light load. Be right on the money with more weight.

 

[honald112]

Re: Prop and anti cavitation plate question

Two final questions lol. Is 5700 to much for a 1975 115 evinrude with just myself and light gear, or should I go for a 21 pitch. Second question, is it normal to cavitate alittle when u take a hard turn at WOT. I'm not quite complaining because she never hit 40mph. I just don't want to replace a powerhead.

 

[surrender]

Re: Prop and anti cavitation plate question

If you have a strong tree near by here is how I did it.

 

[honald112]

Re: Prop and anti cavitation plate question

I already moved the motor to the right spot. I'm trying to figure out if 5700 is too high for my Rudy and is alittle cavitation normal at a sharp WOT turn. I had a half tank(12 gallon) light gear (maybe 200lbs) and myself (165lbs). I hit 40 @ 5700 rpm. Should I go to a 21 or leave it. And if I go to a 21 will I have enough of a hole shot to pick up a skiier. I have a 13x19 on a 75 reinell t-1900 with a 75 115 evinrude long shaft once again. Thanks for any advise.

 

[hwsiii]

Re: Prop and anti cavitation plate question

Honald, 5,700 RPM is fine for that motor, and having ventilation in sharp high speed turns is normal. Since you use the boat for skiing as well I would leave the 19" pitch on it. If you decide later you want more speed you can change to a SS prop and raise the motor up even higher.



H

 

[honald112]

Re: Prop and anti cavitation plate question

Thanks a bunch for the great info. I just didnt know if that was alittle too high for the year it is and being the orginal powerhead and i can bet my last doillar its never been over 5100 rpms. ran and checked all the vitals and seems toi be holding up. you guys kick *** and thanks again

 

[hwsiii]

Re: Prop and anti cavitation plate question

You are very welcome.




H