Ok, I need some advice, suggestions, and another beer. I'll take care of the last one. I have been thinking about tweeking my rig out, to try and get the most economical and correct performance. On the 250 HPDI I used the old prop off my last boat with a yammi 225, it was a very good prop, SS 15.25 x 17 (big wheel). I could only get about 5100 out of it WOT, and 40 MPH on flat water with a light load. One characteristic was, it cavitated heavily up until about 20 MPH then "bit" and seemed to grab pretty good.
So I went to the local prop shop "accu-Prop" and explained my numbers, they said we should take 1" of pitch out, and ventilate the prop hub. The ventilation will help to eliminate the cavitation, and the 1" of pitch reduction will get your RPM up to spec. $125.00 later (today) I pick the prop up, go home, install and dump it in. Ok, the hole shot did improve slightly, it still cavitates some but grabs pretty quickly. The problem is, I feel like I have lost my thrust once up on plane, where before I was turning 3800 and 28-30 MPH, now I am turning 4200- 4400 to make that same speed, with fuel burn up. Top speed is now 38 ( 2 MPH loss) but I can squeak out 5400 trimmed up.
I'm not a speed freak, but now it feels like the 4000-5000 range is really sluggish, I guess because I have less bite... do I need to drop in diameter and increase pitch?? Like my title says, this all sounds like FM to me... I'm a good mech and electrician, but this prop schitt is starting to get on my nerve..
Thanks guys
Marc
