Hello everyone, I have a '96 Procraft V150-B bass boat with a '96 90hp Mercury (2 stroke). My current prop is a stainless 21pitch Quicksilver. Speedometer on my depth finder at full throttle reads 42mph. I have clocked it one time at 46mph with a gps headed down river. I am looking to get more speed out of it while keeping a decent holeshot. A local boat shop has a used 24 pitch laser ii prop for a decent price and I'm really considering buying it! At the same time, my tachometer has not been consistent in the past and I'm not really sure what rpm the engine runs with the current 21 pitch prop. The engine rating is for max 5500rpm, that's all I know. I have read in some older forums that people are getting 50+ out of the same boat. I guess I need to know if a 24 pitch prop is too much, and also how to know what rpm my engine should be at full throttle. Thanks in advance for any tips or input!
Seconded ;without a reliable tach reading it is just guess work.Also the only really accurate everytime speed is gps.
In the meantime check your setup.
The antivent plate just abover the prop should be about even with the bottom or slightly above.
Ok, so I think I caught my tach on a good day, it seemed to be reasonable accurate. First I ran the boat with my current prop(21p) wot at about 5600 rpm and it gps'ed at 43mph. I then changed to the 24p prop and rpm lowered to 5200 rpm at 45mph. To me the loss in hole shot isn't worth 2mph. This prop is significantly bigger than my original. Should I leave it alone or try to find a 22p prop that's the same style as my current prop in order to try and get my rpm less than 5500?
I think your tach is in the ball park but I think it is reading high the 21 was at 11% slip the 24 at 12%.
I think you still need to varify the tach. If the tach actually should be reading 5300 at 43 slip would be 6%.
The antivent plate (anticavitation plate) Is the plate just above the prop that is intended to limit venting
sometimes called "cavitation" in error.
If the plate is too low you are dragging too much motor through the water.
Usually ends up even with or slightly above the bottom.
In the extreme sometimes you can gain a couple of mph just by raising the motor.