Late night gamblers? Boat speed?

mooseknuckle · #1 08-20-2011, 09:48 PM

So in anticipation for a day on the water tomorrow I thought I'd get some guesses on MPH for tomorrow. Here's the deal. I switched from a 15 pitch (pretty beat up) prop on my 75hp chyrsler which I managed to get 33 MPH out of to a brand new 19 pitch prop. I'll have the same boat, set up, and weight. So my question is what's your guess on MPH? Obviously the wholeshot will be less but I'm looking for SPEED!!

npauls · #2 08-20-2011, 09:55 PM

Depending on what your RPM's were before you changed props will determine what kind of speed you may get. If you were maxing out on RPM's wit the 15 pitch you may not even be able to reach full RPM's with the 19 pitch. I also think it will probably be a dog out of the whole shot with the 19 pitch and may have a really hard time to plane out.

Nate

mooseknuckle · #3 08-20-2011, 09:58 PM

I know it will lack wholeshot wise but I've used this prop before and getting on plane is not a problem! I just never checked the mph on it and just recently had the prop completely refinished. Just curious and a little bored. So come on Nate just throw a number out there!

pseelk · #4 08-20-2011, 10:05 PM

I"m guessing somewhere between 5 and 10 mph wound right out.should be interesting to find out .Why did you go back from the 19 to the 17 in the first place and how much speed did you loose?

mooseknuckle · #5 08-20-2011, 10:11 PM

Quote:

Originally Posted by pseelk

I"m guessing somewhere between 5 and 10 mph wound right out.should be interesting to find out .Why did you go back from the 19 to the 17 in the first place and how much speed did you loose?

Actually going from a 15 to a 19. No real reason just tinkering one day and thought i should learn myself on how to swap a prop. After searching for a year for new props for this ancient motor I finally decided to just have the prop refinished! Did the 19 first and the 15 will go in next week. If I go from 33mph to 40 I'll be doing back flips at the boat launch, but I just thought it might fun to guess what sort of increase I may achieve?

pikergolf · #6 08-20-2011, 11:38 PM

In theory 41.8, plugging in the variables might pull 40. Don't hurt yourself if you do the backflips.

Kim473 · #7 08-21-2011, 05:50 AM

I will say 37 as it is only a 75hp. If it was a 100hp or more I would say 40 Funny tho that the seadoos will still pass you.

thenaturalwoodsman · #8 08-21-2011, 07:39 AM

35 MPH, is my guess

209x50 · #9 08-21-2011, 07:39 AM

Probably not much. I'd really watch the RPMs. 2-strokes die just as fast from being lugged and under reved as over reved. All my years running boats and all the props I've had rebuilt I can't ever say i actually had one that impressed me - or was as good as a new one.

mooseknuckle · #10 08-21-2011, 08:16 AM

Thanks guys/gals. Off to the lake the conditions are prime with almost zero wind. Update coming......

Shmag · #11 08-21-2011, 10:28 AM

I too would love to sqweeze another 2-3 mph out of my boat, but as 209 said i would really watch your rpm's. Find a range where you should be and prop your boat to be in that range. If you were not over-reving with a 15 pitch than i dont think you will have the rpms the motor wants for a 19 pitch.

Also merc is coming out with a cheap line of props...aluminum 4 blades for boats in that hp range. I beleive they are called the spitfire, they might be what you are looking for.

Anyways, i will play and say nothing gained in speed. If it was going to a 17 pitch from a 15 then yes a few mph gained but up to a 19 pitch i dont think your motor will spin it fast enough to gain speed.

mooseknuckle · #12 08-21-2011, 05:27 PM

After a few more seasoned boaters recommended not using the 19 I gave it one quick shot. Gained 1-2 mph lost some rpm,s. 19 is better as a spare prop I think I'll have the 15 fixed up a bit and stick with it, much better wholeshot, especially when you have the kids in the tube!! All in all though fantastic day beauty weather a bit busy but that just ment there were lots of really nice looking women in their bikini's! Yes I'm a dirty old man!

pikergolf · #13 08-21-2011, 05:39 PM

Quote:

Originally Posted by thenaturalwoodsman

35 MPH, is my guess

Winner?

benamen · #14 08-22-2011, 06:39 AM

Find the max. rpm range for your motor and check to see if you are within that range or not with either of the props. Like mentioned earlier, lugging any outboard will definitely shorten its life. Years ago when my father did a lot of boating, he would get a prop re pitched if he thought that would help at all. Just thinking a 17 pitch might be more of a happy medium.