Change in pitch

[Riegfrghtl]

Hey guys, Hope everyone had a safe and wonderful fourth of July. I have a 1972 Cruisers, Inc Bonanza with and 888 Mercruiser (188hp). Approx. weight with 40 gallons of fuel, 3 people, and some gear 4000lbs. Current prop is a michigan wheel aluminum 15 1/2 x 19P (model # smc378). Mercruiser WOT for motor is 3800-4200 rpm. With current setup and weight stated above my WOT is 3800 rpm and speed is 39 mph (GPS). I am curious if I drop to a 17P if my rpms will get closer to the 4200 rpm max and maybe gain a few mph or a better hole shot. Any thoughts or ideas would greatly be appreciated. Thanks!! Tim

 

[steelespike]

Re: Change in pitch

Yes 2" will add 300-400 rpm.and should improve your hole shot. Usually if you stay with the same brand results can be more predictable.

 

[Riegfrghtl]

Re: Change in pitch

Yesterday I took the boat out and did some trial runs. The fuel tank was nearly empy so I filled up and and add some stabil ( the fuel in it was from last fall). The fuel at the marina was 93 octane. I also change fuel/water filter. Took boat out ( me only) and was able to to reach 4100 rpms and 43 mph (gps). I felt that the boat was running pretty much as well as it could. Later that day I took myself and 3 more adults (around 800lbs total) out and the boat took a real long time to plane. Topped out at 3700 rpms and 37 mph. Took alot of throttle adjustment to keep on plane. Either it was too much throttle or not enough. I am wondering if going to a 4 blade solas amita might help getting to plane better and staying there. Currently I am running a michigan wheel 15 1/2 x 19p 3 blade aluminum. Specs on boat are in original post. If I go to a 4 blade what size would be best to keep rpms at 4100 and also would smart tabs help. Thanks guys for any suggestions. Tim

 

[Riegfrghtl]

Re: Change in pitch

I just got back from the lake today and thought I might share some data that I got. The marina where I keep my boat allowed me to test a 4 Blade 14 1/2 X 18P Michigan wheel vortex prop. Specs for boat are in above posts. With me in boat I was able to acheive 4200 rpms and 40 mph. ( mercruiser 888 WOT are 3800-4200). But when I added 3 more adults (600 lbs ) the boat took forever to plane. At 2100 rpms to 2900 rpms it felt as though the prop was cavitating. The prop I borrowed was newly painted and in a little more than 3 hours the paint was worn off the blades. When it felt like the prop was cavitating it was like being in muscle car smoking the rear tires until they finally got grip. Once the boat got on plane the max rpms where 3700rpms and 35 mph. Can anyone give me suggestions on a good prop so it won't take so long to plane with 4 adults on board.? Would adding smart tabs help in this situation? Thanks in advance for your thoughts and suggestions! Tim