Prop change out results, if anyone cares

[Beefer]

My 1984 SportCraft 22' Walkaround with a Merc 488 I/O, Alpha 1 Gen 1 was propped with a x Diameter 19p SS Quicksilver prop. Recommended WOT is 44-4800 rpm. With the 19p, I couldn't get it past 4000 rpm, and it sounded like it was struggling.

Picked up a Quicksilver X Dia 17p SS prop on ebay, and finally got around this week to putting it on, and then finally got a change to sea trial it today.

With the 19p, top speed was 27mph (gps), at 4k.

With the 17p, I hit 32mph today in 15mph headwinds (SCA today) at 4500rpm!

I also noticed a considerable boost in my hole shot, and seemed to plane way quicker! I'm stoked!!!

I do have one question though. Why did my max speed increase with a lower pitch? I was expecting to lose a bit on top end. Is it because now the motor is reaching it's power/performance band better?

 

[rallyart]

Re: Prop change out results, if anyone cares

Your top speed is ultimately limited by the horsepower at that speed. Your engine is putting out more horsepower at 4500 RPM than at 4000 so you can push the boat faster through the water. Your old prop was outside of the effective range for your engine and boat.
Because you are now in an effective range you've picked up speed and the improved torque at low speed improved you holeshot.
Don't you just love it when everything works out.

 

[dellsboater]

Re: Prop change out results, if anyone cares

Yes you are now in the recommended power range and have the engine working where it like to be...