Pete, Your 454's should run between 4500 and 5500 RPM at wide open throttle. Getting the right pitch prop is a combination of both the transmission and the diameter of the propeller.
I have always heard that putting the largest diameter practical and using a smaller pitch is always the best way to go. The propeller is like the final gear in the total dirve train with the transmission being first. If you were topped out at 3200 RPM you really need another 1800 RPM to get your engines into thier maximum HP production range. Since you had 18 x 17 props on, to get higher rpms at WOT you need to reduce the pitch (which corresponds to a lower overall gear ratio). There is a "magic" formula for figuring how many inches in pitch you need to drop to get 1800 more RPM. Maybe someone else here remembers it, as I do not have it handy. So to answer your question, putting the 17 x 18's on may or may not change the rpm, becasue you are changing two variables at one time. If you have access to some 18 x 15 or 18 x 13 props, I would try them first. getting the right transmission / prop combination is difficult. I would search the internet for 'propeller calculator' and you can also get some good ideas there too. Good luck, Victor On Aug 28, 9:49 am, Love and Luck <[email protected]> wrote: > Hello Everyone, > > I posted a message last year but never got any responses. I'm looking > for information once again on my engine upgrade. First a little > background.... I have a 1982 Uniflite that used to have 270 hp > crusaders, 1.91:1 Velvet drive Transmissions, and 18 x 17 inch props. > My boat would only cruise between 12 and 15 knots. I decided to > upgrade my tired motors and put in a pair of used 350 hp crusaders. > The motors I bought came with 2.57:1 Transmissions so I initially > installed these into my boat. I borrowed a pair of 18 x 22 inch props > from a friend and the boat would cruise at 9 knots and top out at 4400 > rpm. At this point I spoke with Sea-cure technologies to find out how > 34 ss was set up from uniflite. They told me those uniflites came > with the 1.52:1 Transmissions and 17 x 18 props. So, thanks to > craigslist, I found a pair of 1.52:1 Velvet Drives and put them into > my boat. Took the boat out for a cruise with the 18 x 22 props, > topped out at 2000 rpm and 10 knots. Next I took off the 18 x 22's > and put back on my original 18 x 17's. Took her out for a run and she > did 14 knots topped out at 3200 rpm. So, my question, will going to > the 17 x 18's bring my rpms up and my cruise speed up? Is there > anyone else out there with a 34 uniflite with 454's? > Thanks > Pete --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "UnifliteWorld" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/unifliteworld?hl=en -~----------~----~----~----~------~----~------~--~---
