Originally Posted by nice.diver
Zodiac GR mk3
2800 pound gross
50 hp high thrust
300 pound boat with gas
200 pound me and camera
26 mph (garmin GPS)
13 3/8 X 13 high thrust prop
what should I try to get more speed
Without a tach you'll just have to use trial and error... I'd try a 15 if I was paying for it (I doubt you'll be over pitched). If you're feeling lucky try a 17 pitch.
Just checked a prop calculator. It says that you're turning right around 5500 rpm. which is the suggested wot (5500-6000). A 15 pitch would be your best bet. It says you should do 27-28 mph with that prop. A friend here has the same engine (non high thrust) on a 14 Boston Whaler... he says he gets arund 26 mph out of it.