Prop question

[chevydude1]

I have a 24' pontoon which i put a 70hp evinrude on i am only able to getting 12mph at full open throttle it has a 17 pitch 3blade prop and no rpm gauge what can i do to get a little more speed

 

[tashasdaddy]

Re: Prop question

1st you need to get a tach, could be a timing light with that feature, or an temp old tach. then you have enough info to work with. but i really doubt you will pick up much speed.

i have a 140 on a 20' 4 blade prop. and alone get 37 mph. load drops speed tremendously.

 

[chevydude1]

Re: Prop question

1st you need to get a tach, could be a timing light with that feature, or an temp old tach. then you have enough info to work with. but i really doubt you will pick up much speed.

i have a 140 on a 20' 4 blade prop. and alone get 37 mph. load drops speed tremendously.

How easy is it to hook up a tach to this I am use to cars not boats

 

[ezmobee]

Re: Prop question

You'll need a tach that will work with outboard motors. Should be a pretty easy install. I added one to my '73 Johnson 85 years ago and it was as simple as a + a - and a gray pulse wire found in the control box.

 

[rickdb1boat]

Re: Prop question

17 pitch is way too high for your setup. A 13" or an 11" pitch would be more in line and would increase your RPM's and most likely, speed.

 

[chevydude1]

Re: Prop question

17 pitch is way too high for your setup. A 13" or an 11" pitch would be more in line and would increase your RPM's and most likely, speed.

Thanks That is helpfull I was thinking about 14 or 15 pitch 4 blade prop but also thinking a rpm gauge might not be a bad investment because new motors are quite expensive

 

[lncoop]

Re: Prop question

Time out. Don't do anything until you know what your RPMs are. Without that knowledge any guess at correct prop pitch is just that, a guess. 17 pitch is most likely too high, but rotating blindly through different props could get really old and really expensive. Find out what your current RPMs are and what they are suppposed to be first, otherwise you'll just be changing parts.

 

[nikogto]

Re: Prop question

I agree, you need to see what your current WOT rpm's are. Is your motor a 2 or 4-stroke? The 70hp 4-stroke WOT range is 5200-5800 rpm's. I would stick with a 3 blade prop, 4 blades are more for higher hp motors and bass boats, I've used them on pontoons before but had better fuel mileage from a 3 blade.

 

[Silvertip]

Re: Prop question

E-bay, right here on IBoats, and Great Lakes Skipper have enough tachs to make your eyes bleed -- and one can be had for less than 50 bucks. Much cheaper than a new prop that you can't use or is incorrect. Install the tach first, then make sure the engine is tuned and making full power, the throttle is opening fully. THEN post wide open throttle rpm and speed (with GPS if possible). Only then can you tell what prop, if any you need.

 

[Boss Hawg]

Re: Prop question

I have a 24' pontoon which i put a 70hp evinrude on i am only able to getting 12mph at full open throttle it has a 17 pitch 3blade prop and no rpm gauge what can i do to get a little more speed

I kind of relate to the frustation of the prop/no tach issue :redface:
I just installed a '87 Johnson 110 on my new to me '86 20' pontoon that had or has no instruments at all - All i had was a 13x19 & a 13 3/8x17 so i went with the 17 pitch- All felt good & ran as fast as i wanted to go in a pontoon with a little throttle left
BUT i feel the need to know if i'm proped right for the sake of my motor

I'm redoing a 24' Starcraft for my boss that came with a Johnson 90 on it with a 13 pitch but it appears to be a "cupped" prop? Thats what really got me to thinking i need to get my stuff togeather as far as props

 

[chevydude1]

Re: Prop question

I am going to get a tach first thanks for all the suggestions