Owners manual needed 115 inline 6

[joezek]

I have a mid 80s inline 6 115hp, Tower of Power engine. Just got it for my old Mako project. I don't know what diameter and pitch prop to use. My older 50hp Merc owners manual goes into great detail of exactly which diameter and pitch, and even part number prop is needed based on boat size and weight, and hull type. So far all I keep getting is people saying go ahead and try a 19P....well that gets expensive fast if it doesn't work right. Also, I don't know if I need a 13, 13.25, or 13.5 diameter.

So does anyone have an original owners manual or a site to download one? Thanks

JOE

 

[Chris1956]

Joe, An owners manual will not help with you issue. You want to prop it to make about 5500RPM with a moderate load. What kind of boat is it on?

BTW - Normally you will pick the pitch of the prop and the manufacturer will provide the diameter. You usually cannot choose both.

 

[joezek]

It's going on a 17 ft Mako. It's a 1974 model boat. I was comparing different props from Quicksilver and they have quite a few choices. If I wanted a 19P there are about 7 different models and vary from 13" to 13.5". I know a larger diameter alone will change acceleration, efficiency, etc. but they must add all that up before giving it the 19P rating. I just don't want to spend the money on a prop without a proper guide like the one in the Mercury owner's manual. Mercury put the chart there for a reason, and it's pretty accurate- at least the one on my little 50 model is.

 

[Chris1956]

There are propeller calculators, usually one is avail on a prop website. Those are as accurate as the one in your owners manual, I would think. IMO, your boat will need a 17 - 19Pitch prop, based upon the amount of dead rise in the hull, and the load you plan to carry.

I like the 3 blade Turning Point Hustler propellers.

 

[joezek]

Ok I'll look for a prop calculator, thanks