Blow out!

Well I put a jackplate on and now I think I'm experiencing prop blow out (cavitation)

ok heres the deal, the whole reason I built my jack plate was because I didn't feel I was running shallow enough and even when on plane the cavitation plate was still a few inches below the surface even without a loaded boat. With the plate installed at it's lowest setting I am sitting about 2 inches above where I was and set back is about 4.5 inches. I also have a SE200 hydrofoil on my motor (2009 yamaha 20hp 4-stroke)
When I was testing it in the lake I first started with the second to lowest setting which gave me about 3 inches of lift. As I got on plane and speed increased it started feeling like the motor was choking, or someone was tapping the brakes, I tried adjusting the trim setting and it was best when the motor was at a negative angle (hole closest to the boat) but still not perfect. I went back with the JP now adjusted to the lowest setting, 2 or so, and it was a little better, but still very much there.
I decided to take the SE200 off and see what happened. The blow out seemed slightly less, but it was harder to get on plane and stay there and I had some porposing. When I look back as I'm on plane now I can see the top of the SE200 slightly out of the water.
So any suggestions? My thoughts are first trying to redrill the JP, I think I can get maybe another .75" lower. The only other thing I can think of is maybe a new prop. Any suggestions there?
I think if I were running loaded down with buddies, ice, and full livewell then this would be less of an issue, but I fish alone alot too, so.......

 

prop is the stock aluminum piece, not sure of the size. Hey Brett maybe it's a design flaw ;D

 

I don't know what my RPM's are, I was thinking of getting a tiny tach so I can find out. The over reving would make sense, but it starts choking at about 2/3 to 3/4 throttle. Is there a local shop to the bay area where I can buy a tach?
I hope I don't need a SS prop cause thats a bit out of my price range right now.

 

Also how does the motor cut out when it hits the rev limiter? is it a studder, or does it just lose power, cause this is more like a studder.

 

ok before you guys get me all freaked out about SS props and such, where can I go buy a tiny tach today around tampa/lakeland?

 

after calling around all morning I have a line on a tiny tach locally so I may go pick it up. But it's gonna cost me
That's just the price you pay for instant gratification I guess.

 

too late, picked it up a few minutes ago while running around, I'll wire it up after lunch and see what I get on the lake before continuing my height adjustments.

 

ok it's definately not over reving. I bought the tiny tach this morning and have spent about 3 hours figuring it out and running the lake. First I wrapped my upper cylinder and it was showing an idle of 1050-1100 RPMs, it seemed to read better the more wraps I put on it. Then I tried the lower cylinder and it read an idle of 600-650.
Anyway the whole time I was running around the lake the motor whould never get above 3000 RPMs no matter how I set up the tiny tach. Can this be? The range of the motor is 5000-6000 RPM's how can I only be able to reach 3000 at full throttle?
I'm not exactly impressed with the tiny tach, I called to make sure I have the right one and the tech said I did. I don't get why everyone raves about these, there has to be a better product out there to read RMP's, The thing that annoyed me most was the updates every 1/2 second, which really is more like 1 second. I like to be able to see my RPM fluctuations in real time.

 

Well I think I may just scrap the whole jack plate and return to my original setup. I'll set it to the side for the next project maybe. I'm thinking that I may have the prop set as high as I could have with the pocket drive and higher transom already. Building the Jack plate was fun and all, but it's causing me more trouble then it is worth.