Re: what prop to use
i run about 3800 to 4200 rpms now and still have a good 1/3 throttle left to go.
ya need to let everyone know what wot is with the throttle all the way open.... if what ya say is true. i'd guess (w/o knowing what yer wot is) ya need to go to a 21p... maybe even stainless steel.
if i remember right. that's a guess though, ya really need to test it @ wot. generally speaking, decreasing 1'' pitch in prop is worth a gain of 200 rpms. the same pitch prop aluminum vs. ss. is worth a decrease of 100 rpm for the ss version.
in my case, i run a 19p aluminum. i reach 4300 rpm with a normal load. when i got my boat it had a 21p on it, i could get about 3900 rpm. a little more if i trimmed it too high, higher than i wanted anyways (with the 19p aluminum i can get 4400 if i trim to high). i was on the low side for wot with the 21p, so i went down in pitch to gain rpm. i got the estimated 200 rpm per inch decrease in pitch. 21p=3900, 19p=4300. i think i could go to a 19p ss which should bring me to 4200. then i probably could over trim it up and still get my 4300. but since i'm not going to the races i leave it as is. in our case, we have the o ring grove in our lower drive shaft. they commonly break there and a ss prop is less tolerant to a prop strike and transfers the energy into the drive parts as opposed to breaking of a blade of the prop. so i leave it as is. ya want to be on the high side. lugging yer engine isn't good for it. now, let the real prop experts answer your question....
edit... two threads about the same thing...
http://forums.iboats.com/showthread.php?t=285248
