Sorry for the long post, but want to give as much info as I can.
Bought the boat with a 16p 4-blade prop on it. Did work on the outdrive, found out it had been grinding on the spanner nut and chewed it up. Replaced the spanner and can not run that prop without modification, and I do not know if it is the stock prop or not. (Previous owner I have found out, didn't know as much about boats as he pretended to). I had a spare aluminum 19p that I put on for the first run, but turned out to struggle to get on plane, and just was working way too hard. It did have decent top end, but would lose it in any turn and I couldn't back off much or I would continuously slow. I borrowed a buddies 15p large prop just to try, and really like the way it works. Top end isn't quite as much, but it feels close. It is a much larger prop than the 19 though as there is only about 1/2" clearance between the end of the blade and the drive itself, where the 19" will almost squeeze a 2x4 through there. I am thinking of either a 16 or a 17 in the larger diameter, but want some input before a commit. Here is a few numbers from each tested prop.
19P aluminum 3-blade:
Heavy load, major struggle to plane, tops out about 36mph at 3900rpm
Just me on board, still a good workout getting on plane, tops out at 40mph at 4000rpm
Cannot maintain 20mph without either falling off plane, or trying to take off once on plane. It's either 15mph heavy throttle, or move someone up front and all of a sudden I'm going 35mph at the same throttle position.
15P SS 3-blade large diameter:
22mph at 3000rpm
26mph at 3400rpm
37mph at 4500rpm
It performed the same with heavy or light load. Never hit the rev limiter but would not go above 4500rpm (Tach could be innacurate, but seemed pretty close). Planed out quick and seemed to perform well. I could cruise at 25-27mph with ease and planed out very quick without moving anyone around to do it.
Since I got more speed out of the 19p even at such a low rpm, tells me the engine has more torque around 4000rpm. I think I could easily go to a 16p, but "maybe" even a 17p. I am less concerned about going 40mph, but want a good cruise at about 25-30mph with the best fuel economy I can get. Also, should I go with the larger diameter prop, or the smaller diameter? I am thinking a 16p or 17p in the larger diameter, but that's just a guess.
Bought the boat with a 16p 4-blade prop on it. Did work on the outdrive, found out it had been grinding on the spanner nut and chewed it up. Replaced the spanner and can not run that prop without modification, and I do not know if it is the stock prop or not. (Previous owner I have found out, didn't know as much about boats as he pretended to). I had a spare aluminum 19p that I put on for the first run, but turned out to struggle to get on plane, and just was working way too hard. It did have decent top end, but would lose it in any turn and I couldn't back off much or I would continuously slow. I borrowed a buddies 15p large prop just to try, and really like the way it works. Top end isn't quite as much, but it feels close. It is a much larger prop than the 19 though as there is only about 1/2" clearance between the end of the blade and the drive itself, where the 19" will almost squeeze a 2x4 through there. I am thinking of either a 16 or a 17 in the larger diameter, but want some input before a commit. Here is a few numbers from each tested prop.
19P aluminum 3-blade:
Heavy load, major struggle to plane, tops out about 36mph at 3900rpm
Just me on board, still a good workout getting on plane, tops out at 40mph at 4000rpm
Cannot maintain 20mph without either falling off plane, or trying to take off once on plane. It's either 15mph heavy throttle, or move someone up front and all of a sudden I'm going 35mph at the same throttle position.
15P SS 3-blade large diameter:
22mph at 3000rpm
26mph at 3400rpm
37mph at 4500rpm
It performed the same with heavy or light load. Never hit the rev limiter but would not go above 4500rpm (Tach could be innacurate, but seemed pretty close). Planed out quick and seemed to perform well. I could cruise at 25-27mph with ease and planed out very quick without moving anyone around to do it.
Since I got more speed out of the 19p even at such a low rpm, tells me the engine has more torque around 4000rpm. I think I could easily go to a 16p, but "maybe" even a 17p. I am less concerned about going 40mph, but want a good cruise at about 25-30mph with the best fuel economy I can get. Also, should I go with the larger diameter prop, or the smaller diameter? I am thinking a 16p or 17p in the larger diameter, but that's just a guess.