Hey Michael,
That was a good investment having a dealer check out your motor and change water pump! Those impeller blades can take a set if motor is not used for 5 years, and I wonder if that was a factor in the overheat problems you had! If it now turns 5800 after fixing the kinked fuel line, that was evidently why you were having problems with it bogging down before at WOT! Do you know if they ran the BRP fuel system test to measure fuel restriction with vacuum gage in fuel line? (Should not exceed 4" Hg at max fuel flow.)
The
optimum rpm for your motor is 5300-5500, so you're underpropped! Peak HP on your motor is about 5200 rpm so if you wanted max WOT speed, a 20-21" pitch BRP Viper might put you over 50 mph (and create some chine walk!) However I think a a 4B prop will give you a lot more stern lift and would be a step in the right direction. You'll give up a little WOT speed compared to the bow-lifting Viper you're running now, but you'll be able to plane @ 12 mph and basically be able to run at any speed you want with a better ride. Although my data is with a bracket & jack plate with AV plate on top of solid water, based on my experience with the same motor/hull and much prop testing, I think the fastest and most efficient prop would be the 14.5 x 15P 4B SS BRP Cyclone. Should give you about 42-43 mph & ~ 5400 rpm @ WOT and about 4.0 mpg at ~3700-3800/27-28 mph cruise. The next best would be the PowerTec ELE4 4B SS 15 x 15 prop that's a little easier to turn and will give you about 39mph/5450 rpm @ WOT and about 3.7-3.8 mpg at the same cruise rpm. If you want to run an aluminum prop, I think the
4B Aluminum Michigan Vortex 14.5 x 18P prop would be about right. I have a 14 x 20P 4B Vortex that I had repitched to 14 x 18 that gave me 37 mph/5700 rpm @ WOT, so a little more diameter would probably get your rpm down to about 5500. You're welcome to try it if you want. I'll email you an Excel file with my prop test data if you want it. It got about 3.5 mpg @ ~ 25 mph/3700 rpm cruise; larger diameter props are more efficient, so you might do better with a little more diameter. Although my data is with a bracket and AV plate about 6" above keel, my testing was done with over 450 lbs of ballast, so if you normally run lighter than that, less weight may offset the bracket advantages, so your performance should be similar to mine.
Regarding the new roof work, if you haven't also specified the installation of a
waterproof "peal & stick" membrane under the metal, I would highly recommend it! That stuff has a higher bond strength than any wind loads, so even if we have a really bad storm that peals off all the shingles or metal off the roof, your house should stay dry (provided it doesn't take the whole roof off!), plus it's worth a pretty good discount on your windstorm insurance! Denny