Lawdy, not another prop question...

[trucky]

OK, 24 foot basic toon with a 2007 Merc 115 EFI. Current prop is a Solas 13.5 x 15. Top speed is about 23 on GPS at 5000 RPM. Lake elevation is about 2000 feet. I know it's over propped. Mercury says WOT for this engine should be between 5800-6400 RPM.

Assuming the engine height is correct and there aren't barnacles hanging off the toons, my calculations say I would need to drop pitch to about 11 (approx 200 RPM per inch) to get up close to 5800 RPM. That seems crazy to me. Is anyone else running a similar setup with that type of prop?

[smoker62]

My 2012 115 4 stroke came with a 15 - 3 blade. I dropped to a 13 - 4 blade nemesis which is basically a merc Spitfire . Great prop and put my rpms up 200 and gained me a couple mph. I also have an 11 that I ran when loaded with people. The 11 would hit the limiter when I was light. Maybe at altitude like you are it would be the ideal prop . I have a like new 11 pitch 4 blade if your interested.

[Waterlogged]

I am running a 13.75X15 on my boat with a 2008 115 4s efi and can do 31 mph. I can easily over rev the motor. I have lifting strakes. Without them would be a different story.

Glenn

[trucky]

I am running a 13.75X15 on my boat with a 2008 115 4s efi and can do 31 mph. I can easily over rev the motor. I have lifting strakes. Without them would be a different story.

Glenn

Glenn, I understand about the strakes and making a difference. Also, you've got about 2 foot less boat than me, plus maybe some altitude differential. That seems like a great top end for your boat.

[trucky]

My 2012 115 4 stroke came with a 15 - 3 blade. I dropped to a 13 - 4 blade nemesis which is basically a merc Spitfire . Great prop and put my rpms up 200 and gained me a couple mph. I also have an 11 that I ran when loaded with people. The 11 would hit the limiter when I was light. Maybe at altitude like you are it would be the ideal prop . I have a like new 11 pitch 4 blade if your interested.

Great information! I do know the altitude plays a part. I bought a Sea Ray I/O V-8 down in Tampa a few years back. The sea trial there ran great, WOT was right on. When I got it back up the hill here in WNC & TN it was a dog until I dropped a few inches in pitch.

I'm not really looking to make my boat the fastest it can possibly be but want a reliable and long lasting vessel that I know is properly setup. WOT is generally reserved for ducking the incoming thunderstorm or avoiding the consequences of the peepee dance.

I'll PM you about your 4 blade.

Ken

[smoker62]

PM returned. I will also add , I ticked 27 GPS on the first trip in last summer with new underskinning. I was excited to have gained 2 mph. It never happened again LOL. I chalked it up to clean tunes, new underskin , and a nice crips WI morning on a slight ripple with little gas. 25 was a regular trip . That 13 pitch 4 blade was a great prop.
http://www.qsprops.com/aluminum/nemesis/