Propeller Help Needed

jeep187

Petty Officer 3rd Class
Joined
Oct 2, 2008
Messages
89
I have a 2007 Sweetwater 1880 Tuscanny Pontoon Boat. It has a 2006 Yamaha 50hp 2 Stroke. (regular 50). I usually run 3 people on it. I have 2 Batteries, 18 gallon Fuel Tank, and about 200 lbs gear.

At full throtle i am running about 5400 - 5500 rpms with a 12 1/4 x 9 aluminum Prop.

Does anyone have any recomendations on a different prop size?

Thanks in advance.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Propeller Help Needed

Why do you need a different prop size for, speed or better push ? With that prop, seems you are very near the max rpm for that engine's best speed.

Happy Boating
 

jeep187

Petty Officer 3rd Class
Joined
Oct 2, 2008
Messages
89
Re: Propeller Help Needed

I am looking for better speed. It pushes good. But it seems like it could use a little more top end. From about 3/4 throttle - full it doesnt go any faster

I normally run 3 people and it runs at 5500 rpms and with 5 people it runs 5250.
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
Messages
12,345
Re: Propeller Help Needed

(1) Run one person with that configuration, what's the max rpm achieved ? check what's the max rpm factory recommended for that engine and substract from (1)

Example: max rpm at wot 5,600
Max factory rpm at wot 6,000
Difference: 400 rpm off (each 1" pitch more/less prop difference is 200 rpm) maintaining same size prop. So about 2" less in pitch to obtain max wot speed.

Matching top speed to max rpm for that engine will increase top end speed, but will sacrifice hole shot, check with gps 3/4 to full wot to see if obtaining same speed, probably speed difference is minimum to feel it in that throttle range.

Happy Boating
 

jeep187

Petty Officer 3rd Class
Joined
Oct 2, 2008
Messages
89
Re: Propeller Help Needed

The manual says Full Throttle Opperating Range is 4500 - 5500 RPM

With 1 - 3 people on the boat i run about 5500 - 5600 rpm at WOT

So would you recomend i go from a 12 1/4 x 9 to a 12 x 11?

Or what is your recomendation?
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
Messages
12,345
Re: Propeller Help Needed

If you already are reaching 5500-5600 for an engine that's has factory rpm parameters of min 4500, max 5500 at wot, you already are at the max rpm limit for that engine, your achieved actual speed at wot is your final top speed, do not exceed 5500 rpm with any prop, you could blow your engine :mad: The max is the max.

Happy Boating
 

jeep187

Petty Officer 3rd Class
Joined
Oct 2, 2008
Messages
89
Re: Propeller Help Needed

What if i go up in pitch from a 12 1/4 x 9 to 12 -11. Won't the RPMS drop and speed pick up?
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Propeller Help Needed

Going up 1 pitch should lower rpm by 200 rpm, 2 pitch 400 rpm and so on, by speed pick up you mean bettering 3/4 to full throttle speed that seems the same with actual prop ? Ideal would be to test 2 next close higher pitch props and see performance difference. This is not a exact science, it's a matter of trial and error issue to obtain what you are looking for.

Happy Boating
 
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