Looking for prop ideas..

[Chemdawg]

Hello everyone. I know this gets rather repetitious, but here is what I have:

1987 Arrow Glass Carisma 175. 17.5' Fiberglass
1987 Mercruiser 3.0 with Alpha one drive

I have a prop here that is cracked that is a 19pich, and the one that's on the boat, I have no idea what it is. I cannot see the markings anywhere.

When I take it out on the water, I can hit about 30 mph with myself and two kids. So total people weight of about 325 lbs and not much gear at all. I am sitting at about 4200 RPM, and I am not at full travel on the throttle lever.

From everything I've read, it sounds like the 4 blade prop is the way to go, but I'm not sure what pitch to look at. I want to have speed, at WOT, and stay within the recommended RPM range. Holeshot is not an issue. I don't pull skiers, but we will be pulling a tube.

So... Ideas?

Thanks, Pat

 

[steelespike]

Very likely your prop size in near the base of the blades or under the prop nut.without the size we can't evaluate your setup.
I can tell you that a boat like yours would normally have a 19" or 21" prop turning 4600 to 4800 wot rpm at speeds around 40 mph.
​ Can't tell your setup without your wot rpm and gps speed.

 

[Lager]

Ive got a boat that looks like yours and has the same power plant.
Im betting your speedo is incorrect, because you should be going a bit faster then you posted.
On mine, using the 19 inch three blade, I get 42 MPH at 4200 rpm.
You might want to check your speed using a GPS, Since I dont have a power outlet? I just use my cars GPS and run it using its battery power. Ive also found my original tachometer was not very accurate also, that why I installed a new one.
Since I wanted to pull a skier and a tube, I installed the Solas 17 inch alum 4 blade they have on here and the difference was noticeable.
Boat now launches well, holds better in sharp turns. But now top speed is 36 MPH @ 4500 RPM.
Im glad I have both props, the 17 inch has its uses, but when I want to just cruise the lake with the wife, the 19 inch provides me with a smooth riding 30 MPH @3000 rpm and just sips gas @ that rpm and speed.

 

[MikDee]

You've got to wind your motor up the max rpm with that 17" prop you have on there, for us to figure your engine health, and reply. A few runs over the recommended range (as long as it's short runs to get the data) shouldn't hurt anything because you are close to the right size prop now.