Prop size

"The boat I bought, a 1975 Win

"The boat I bought, a 1975 Winner tri-hull open bow / 120hp mercruiser came with three props. A small, medium, and larger diameter. why three different sizes and which one is the best choice? The main things we will be useing it for is fishing or just packing a lunch and takeing the dog out for a weekend cruise. Now and then we may go out and pull a tube around for some fun when the niece's and nephew's come visit. We live on lake Oahe in northern South Dakota so there is a pretty good amount of water to cover so we may be cruising a few miles up or down stream depending on what we're doing."

"[url=""]http://sites.mercurym

"http://sites.mercurymarine.com/portal/page?_pageid=126,48417&_dad=portal&_schema =PORTAL

try this."

"Think of your prop kinda like

"Think of your prop kinda like a multi-speed transmission on a tow vehicle.

The smallest prop will allow you to push more weight without over burdening the motor, but will result in the lowest top end speed (assuming the pitch is similar).

The largest diameter will theoretically give you the best top end speed, but only if the load is light enough for the motor to reach it's optimum rpms without bogging out..."

"One measures 14 1/2in. and th

"One measures 14 1/2in. and the number ends in -21p. The other one measures 15 in. and ends in -17p. The third one measures 12 in. and ends in -21 but no p after it. Now the 14 1/2in. 21p one of the blades measures about 1/8in. longer than the other two. The 15in. 17p one measures about 1/8in. shorter than the other two, and the 12in. they all measure the same. Can and/or do they need to be fixed and which one would be my best app. for my boat?"

"Try this site for help in pic

"Try this site for help in picking the correct prop
http://turningpointpropellers.com/"

I also bought a boat that came

I also bought a boat that came with several props it came with a 14x19p and a 14x17p it ran 50 mph with the 14x19 but labored badly trying to get on plane. The 14x17 quit at about 38 mph . I bought a 13 3/4 x15p stainless steel it gave me the best all around performance . Maybe try each prop with the normal load you would carry and see how they perform and if they stay in the engines max rpm range