Help me Help me!

[chiefalen]

Oh masters of the prop world, would you shine your grace and knowledge on this worthless mortal boater with a few words of wisdom.

I have in my signature boat a new/old motor.

140 hp merc. i had a 120 hp before the transplant.

I am running a 13 3/4 x 15 prop @ 31 mph gps verified @ 4600 rpm max.

Boat don't go no faster.

With the 120 i never got above 27 mph with the 15 prop @ 4000 rpm.
With the boat loaded with 4-5 fat relatives i would install a 14 x 11 cause i couldn't even get on plane with the 15.

Now to the question, Would a 14 x 17 give me another 5 mph And drop me 300-400 rpm?

Or would a 13x19 do the same.

Reason i am asking is im a little confused about the inch, vs pitch.

I do not want to go below 4200 rpm.

This is not a speed boat but a heavy old style cuddy.

Not water logged. Not a dirty bottom but trailered.

Thank you in advance for any guidance offered.

 

[Bondo]

Re: Help me Help me!

Now to the question, Would a 14 x 17 give me another 5 mph And drop me 300-400 rpm?

Ayuh,.... In Theory maybe....

In reality,...
You'll drop the rpms by atleast that much, with No increase in Speed....
Probably a Drop in speed, due to the fact that the motor just Doesn't have the HP to turn it...

 

[chiefalen]

Re: Help me Help me!

Stay with what i have?

 

[patiomae]

Re: Help me Help me!

I think you're best calling a prop shop. Most will give you free advice. Try Midwest Propeller. I posted their info on another thread for a guy with a similar problem and he said they were able to help...
http://www.midwestpropeller.com/index.html

 

[steelespike]

Re: Help me Help me!

I think you need more than a simple pitch change.Are you getting full throttle?good compression?carefully timed/tuned?Full trim?Does the bow seem to get up ok? You need a prop to help get the boat up.I'm not expert enough to give much detail.But the Hustler Turning point prop is said to have close to stainless performance for aluminum prices.I think I would stick with the same pitch.5mph would be a stretch but I have read some good results with the turning point.I would think with a light load you could approach mid to upper30s. It must have been a real slug with a 120.I couldn't find a listing for your boat but it appears it is at least 2,200 lbs with the 120.

 

[chiefalen]

Re: Help me Help me!

I always meant to get it weighed never did.

But it is heavy.

Sir: i do not wish to sound as if i am bragging, however this motor is running the best it can.

As was the 120.

With the stringer it's manual trim.

Timed, tuned, believe me if i tell you all running the best it can.

Thank you all for taking time in your busy day, to read and respond, i wish you all well.