Looking for a starting point.

[bonz_d]

The Alumacraft Classic 16 that I recently purchased is in need of a prop. The boat originally came with a 1988 Evirude 70hp that was damaged and not running. But with this boat and motor were 3 props, believe they are 3X13X17 or 3X13X19.

Anyways, I've repowered this boat with a 1975 Johnson 50hp that runs really strong and has great compression for it's age. This engine came less a prop and am currently looking for one to start with. Looked at new and have a couple leads on s few nice used ones.

By looking at the new ones I see the size ranges and am thinking 15" to 17" pitch. In the 15" pitch I see the dia. range from 11 3/4 to 12.5" The 17" pitch range from 11 3/4 to 12".

So looking for a best guess as to where to start. Boat and engine are 750#, trolling motor and 2 batteries, one 6 gal or one 12gal fuel tank, passengers and gear about 600#. So roughly about 1500# total weight.

 

[Don S]

Re: Looking for a starting point.

Since you dropped 20 hp, start with the 15 and see what your WOT rpm is. Adjust prop size as needed to get into your engines WOT rpm range.

 

[bonz_d]

Re: Looking for a starting point.

Thanks, Don. How about diameter? Seems most are 12 1/4" with one being 11 3/4" and one being 12.5" Hoping to get close the 1st time.

 

[steelespike]

Re: Looking for a starting point.

A 15 seems a good start to me as well. Diameter is a secondary consideration. A 1/4" inch difference will have little effect.
I would be more concerned that you get a good quality prop. See if you can find a Solas Amita,these have a good reputation for performance and predictability.

 

[mpsyamaha]

Re: Looking for a starting point.

I agree on starting with a 15p prop. Dont worry about the diameter, its the pitch that really matters. Diameter is more a result of the specific blade design/shape of the particular model prop. If the first prop works out well, then great... if there is obvious room for improvement, post results on here and im sure you can get plenty help in picking the perfect prop. And then you can keep the first prop as a spare.

 

[bonz_d]

Re: Looking for a starting point.

Thanks, at first I was thinking a 17 pitch until I actually added up the weight.

One of the reasons I was looking at used ones is because they can be had pretty cheap. About 1/2 the price of a new one for one in decent shape that isn't all chewed up. Also figuring that would give me a base line to start with. A guy down the road from me has a very nice OMC part number prop that is a 15" pitch that he's only asking $50.00 for. Sill has 99% of the original paint on it.

Next, I am running a SS 10.5X11 on my 35hp Lund and I really like the way it performs so down the road I'll probably be looking to SS on this one also.

 

[1FASTLASER]

Re: Looking for a starting point.

steelspike your pm box is full..