prop difference

C

cuzzx

Seaman
Joined
Oct 14, 2007
Messages
74
IF i had a 20ft pontoon with a 75 hp motor running a 13 3/4 x 15 alu. prop,

and I put a 14x13 on what should happen?
 
Randybeall

Randybeall

Petty Officer 1st Class
Joined
May 2, 2008
Messages
319
Re: prop difference

I would suggest that you read several of the other prop posts before continuing here. You need to supply quiet a bit of important information to get any kind of a reasonable answer. The most basic is what is your engines rated max rpm and what is your current wide open throttle rpm. With out information you can not make any kind of educated guess. Another point is what do you want your boat to do? Hope you will repost with more information so we can help you.
 
C

cuzzx

Seaman
Joined
Oct 14, 2007
Messages
74
Re: prop difference

Have a 20ft pontoon that is rated for a 75.
Running a 75hp Mariner , prop is 13 3/4 x 15 , at 5050 rpm.
Book says 5250rpm.
Gets 2 miles per gallon at wot.
Not real sure about speed.

13 3/4 x 15 prop, Toon running around 3300r's, it runs good and smooth, then open it up ,WOT. Motor seams to not run just right, bogs /laggs, something to that effect. Thinking about dropping in pitch but they don't make a 13 3/4 x 13 for my motor that I can't find. So whats your thoughs on a 14x13.

Have just bought this motor and run it 3 times.
2 times with old 13x19 prop and 1 time with 13 3/4 x 15.
Running the old 13x19 it would hit 3000 then slowing move up to 5000. I think prop was slipping so I put the 13 3/4x15 on.
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: prop difference

5,050 is pretty close with the 15 a 13 would put you at about 5450.
perhaps a little too much. but might be good if you run with a load a lot just keep it around the 5250.
A 75 will use about 7.5 gallons per hour(GPH) at wide open throttle(WOT)
most pontoons driven around 6-12 mph will get very respectable mileage.
What speed is best depends on the setup.
 
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