Prop sug. Wildfire/Sidewinder

[monigripp]

I know a few of you have had had a late 70s early 80s Wildfire, I believe it was also manufactured as a Sidewinder. 16ft w/115 tower that runs absolutely perfect after all these years.
Boat only turns 4800RPM w/current prop, Id like spin it a little higher, problem is, the prop is painted so heavily on the numbers that nobody can read the final one. All we can tell is that it is 2?. pitch. So I guess Im starting from scratch, any ideas on what to run?
The boat pulls like a champ out of the hole considering what it is, pulls 2 tubes out of the water VERY easily, but Id rather gain a few mph
No jackplate, no setback 115 merc runs indicated but doubtful 53 mph@4800 right now
PS Anyone w/cheap & relatively fast stream get in touch if your selling

[vector mike]

4800 is too low of an rpm at WOT. It will put an unnecessary strain on the motor. It's like taking off in your car in 5th gear. You need to scrape off the paint to see what it is and then go down 2 inches in pitch and possibly 4. You should be about 800-1000rpm's higher than that. I used to spin my tower-of-power 150HP to 6200. You will not only gain holeshot but possibly even more top end. 53mph is probably stretching it but it could be possible.

[vector mike]

I just figured out that at 4800rpm with a 2:1 gearcase and 10% slip at 53.2mph you shlould have a 26pitch prop. That is really hard to believe that that motor can even turn a wheel that big.

[monigripp]

dont take it the wrong way about the speed, like I said, it is only on the speedo and thats all I have to judge. A friend has a 30 something pachanga that has gps but only does 44 flat out, and my boat walks his pretty well, but its all estimated beyond that 44mph number
Ive seen some heated arguments about these boats top speeds in other places on this board and certainly am not trying to start another one here, just want the best prop for what I got
I didnt even think of scratching the paint off.
you really think I should go as far as 4" down on the pitch?
How much pitch = rpm gained

[monigripp]

scraped the paint
23 pitch, 13" diameter aluminum prop on the boat
what should I go with
im thinking 20-stainless
is this a change I will really notice?

[225RANGER]

Just an idea, but if it your boat is that good out of the hole, check the tach. If you go to a smaller pitch and your tach is off the results could be, even better hole shot,same speed and a very expensive rebuild! I have seen tachs off as much as 1000 rpm. Check it out before you accidently spin that tower up to 7000 grand. They will take if for a short time, but before you know it Bang! Try another tach or find a tech that will go for a ride with you and allow you to use his equipment to verify your rpm. Another note, just testing it at idle at the marina will not give you an accurate reading. If your tach is off you might not notice it a 800rpm. It will get worse the higher the revs.
Kevin

[vector mike]

Well, assuming that your tach is accurate you should be running 47mph at 4800 with 10% slip with the 23. If it were me I would go with a Laser II in a 19 pitch. I tried a couple of different props on my Viper when I had the 150 tower-of-power and that prop seemed to work the best. I ran a 24 pitch though.

[monigripp]

seems like speedo error is more likely than tach, but will check the tach now that you got me worried.
thanks for the help S&F
should just by a stream and be done with it, but its impossible to sell this boat for good money, I paid too much, nice little boat, but regretting it

[Hot Shot Merc]

I dont remember what size we ran when I was 9 years old but after changeing to the 150 in line we ran 70 mph on the old school speedo.Heres a picture:D

http://home.comcast.net/~hotshotmerc/boat4.jpg

[vector mike]

Com'on Rob,
We both know that 70 mph with that setup was dreaming.