What size pitch on prop
Buddy of mine is running a 1998 yamaha 200 with a 14 1/4 x 19pitch on his 1993 bayliner trophy with the 2 seater top, you think this is the proper pitch for fuel consumption or speed. I know wide open it will run about 45mph with the top down and about 39 with it up and cruise at about 32 but not sure if it right for fuel. One other problem he had is when he would get up to cruise the boat would lean to the passengers side and it would take my 200lb. ass to stand up behind him to level it out what would cause it to lean that way the thrust of the motor?
Proper Propeller pitch
is when the boat is loaded for it's standard trip, full fuel, the engine reaches right at to 100 rpm below it's maximum rpm rated for the engine. This keeps over reving the engine to an impossible level with a novice skipper, and also provides the boat with it's maximum efficiency. If the boat goes out in various loading conditions, it is nice to have different props, but usually not a necessity as the "standard trip" is the usual the boat will encounter during it's life span, and anything else is just once in a while and not that inconvenient. Fuel economy can be improved by proper trim, proper boat loading, and not running at wide open throttle. You might find that at 5900 RPM the boat goes 42, but at 4600 RPM the boat goes 36, and at 4000 rpm the boat goes 30. So, you lose six MPH while decreasing 1300 RPM, and another six mph while only decreasing 600 rpm, so it would be a good guess that the boat is most economical at 45-4600 rpm. Also, a fuel flow meter would be better at getting a skipper to the most efficient fuel flow numbers. Other ways to stay efficient is to plot straight line, shortest routs on a gps prior to starting a trip, letting the skipper follow straight lines to the destination instead of wandering and wasting distance/time. These are the guidelines that I know of for proper propeller pitch, hope this information was helpful.
The leaning is just the boats response to the torque of the engine, and is in the opposite direction of the prop. It can be offset by loading more gear to one side of the boat, shifting passenger's, or the best way is to install hydraulic trim tabs on the boat and trimming level with those.
Last edited by Chris_Stout; 02-27-2008 at 02:52.
Pitchs & Props
Wish there was a simple answer. But for some extra insite check out www.piranha.com, find your motor type, year, HP and there is a chart that relates to speed pitch and so on. Same motor on a little different boat would change the whole deal. But it's info.
thanks guys i found out from him that at wide open with loaded boat it's pushing 5500rpm at 39mph. and the motor is a 95 not 98