1966 crosby sled

[doughboy19]

I have a 1966 crosby sled with a 1971 Mercury 50 hp 500 the prop is a 10 1/2x 15p. The motor runs fine after rebuild and planes fine with just me in it. My question is what do I need to do to get it to plane with 2 people in the boat pulling a tube, lower pitch prop? or what? No tach but I know it runs no where near 5500 rpms with the load on it. Please help!!!!!

[steelespike]

You shouldn't make a prop selection without your present prop size,max rpm and speed.
Your taking the life of your motor in your hands without reliable rpm and speed info.
You also could end up with a boat that performs poorly.Rated rpm is 4,800 to 5,500
with todays doctored fuels most suggest rpm near the top.My 65 Merc 500 on a 330lb 57 Crestliner Bucaneer 18 boat runs an 11 or 12" pitch.I'm the second owner and haven't had it on the water enough to get a tach for it.I can tell you it is a large light boat that gets up on the water easily.