Spray from Leg/ Prop??? + RPM/WOT question

[WIrED]

I have a 16 1/2' with a 90HP IL6 ...The issue I have is that, the faster I go...a "V" shaped spray shoots up about 4' at top speed (32mph)...The boat had hydofoils on it....I took them off last night and went out...it still does the same thing tho...but only with a few mph difference(slower)...no matter which way I seem to tilt the motor(manually)it doesn't make much difference...<br />Can this be caused by the motor sitting to low in the water?....<br />Where should the cavitation plate be relative to the bottom of the boat?....<br />I cant think of anything else to add to that question...any suggestions would be gr8..<br /><br />Next question <br /><br />This may or may not have anything to do with my last question(or maybe it does)<br /><br />My boat seems to get top speed(32mph) at about 4700 rpm....the tach(motor)will go to 5700 rpm ..the last 1000rpm's seems to have no affect on any speed just....higher rpm...could that be something to do with my last question...or is the motor propped wrong....right now it has a 3 blade prop...I cant tell what pitch it is..all i know is "out of the hole" it gets up to speed very quick...<br /><br />Hope this is enuff info....I will offer more is more is needed...<br /><br />THX

 

[WillyBWright]

Re: Spray from Leg/ Prop??? + RPM/WOT question

Definately sounds like the motor is too low on the transom. Plate should be about level with the hull, an inch high or low depending how you want to use the boat. If you happen to have a longshaft motor on a shortshaft boat, it'll do what yours is doing. A shortshaft transom is about 15" to 16" high. Longshaft transoms are 20" to 21". (The transom is at an angle. The figure 15" or 20" would actually measure perpendiculaly with the theoretical plane of the water. Since it's at an angle, the actual transom measurements are a bit longer.)

 

[youngboater]

Re: Spray from Leg/ Prop??? + RPM/WOT question

on my mercury prop if you look on the side there is a number. By looking at it I was able to tell the pitch etc. It had a code then I saw a p17 for pitch 17 maybe your prop is like this?

 

[Gus Mortimer]

Re: Spray from Leg/ Prop??? + RPM/WOT question

It sounds like you have the same setup as I do. My anti ventilation plate is flush with the bottom of the transom and I have a very little spray (just to eithor side of lower leg) but when coming off plane it will begin to throw those sprays so maby yours is to low.?]<br /><br /> Oh and I dont know how much your boat weighs but mine is just under 1100 without the motor and I have a 19p prop and it jumps on plane and tops out at 43

 

[fishhawk16]

Re: Spray from Leg/ Prop??? + RPM/WOT question

Wired<br />I had a similar problem with the 'V' spray except mine was more like 12'. I raised the motor 1 3/4 " and this resolved the problem.