Which prop would you use

[magster65]

I have tried 2 props and can't decide. Which would you use? This is the boat... a 1992 24' Sea Ray cuddy with a 5.7 / alpha (1.5-1 gearing), 400 (adult) hours on it and runs great. So with 2 people and full fuel and water...
Both props are Mirage ss units.
19"p : wot = 44 mph @ 4050 rpm and 32 @ 3000 rpm cruise
17"p : wot = 42 mph @ 4500 rpm and 29 @ 3000 mph cruise
One other variable maybe is that these hulls have small lifting strakes on the 2nd chines from center (no it's not hooked). That makes them kinda' 'hit the wall' at 42 to 44 mph it seems. The 19"p will still plane instantly and doesn't sound like it works the engine until 3600 or so then the strakes start pushing the nose down. When I'm boating I rarely go full throttle but do occasionally for short bursts, I'm mainly a 3000 rpm +/- guy. Any thoughts are appreciated. Thanks!

 

[a70eliminator]

Re: Which prop would you use

I hear the closest to the upper RPM limits is best.

 

[Bondo]

Re: Which prop would you use

Ayuh,........

The motor is Lugging with the 19"..........

 

[MikDee]

Re: Which prop would you use

Nice Boat! Definitely the 17" pitch, it lets your motor unwind to the proper rpm range.

 

[rndn]

Re: Which prop would you use

What everyone else said. The 19 is causing your engine to work too hard. Like taking off on a 10 speed bike in 10th gear as compared to 1st gear. An extreme example but you get the point.

 

[TilliamWe]

Re: Which prop would you use

What is the max WOT rpm of that engine? If it's 4600, then the 17 is the way to go.
If it's 4400, then have the 17 worked a bit with some cup to get the rpms down to the 4400.
Either way the 19 is not good.

 

[magster65]

Re: Which prop would you use

That's what I figured too but those lifting strakes throw a variable into this mix. I've been in lots of overpropped boats and they're dogs at any rpm. This acts differently. It's really quick on plane with the 19" too and accelerates quickly to 'it's speed'... the roll on is really good too.
I found it interesting that the 19"p makes the boat a little faster. I thought the 17"p would be a faster top speed by unloading the engine a bit... wrong!
So I bought the 17" today.
They're expensive little buggers but they're sure purdy!