Celebrity 290 SC

[SeaHoCaptain]

Hi ... A friend refered me here and hopefully someone can help me out. I posted up in the Celebrity boat section but then saw this section. So I will try here too.

I have a 1990 Celebrity 290 SC (it's a cruiser, 9k lbs). It has twin mercruiser 5.7L with Alph I's. I've learned my props are the wrong selection and I'm trying to determine what originally came on the vessel. Right now I have 21P Mercury SS Mirages (I dont know the diameter) and my top RPM's is only 3900-4000.

I think when we bought the vessel we had aluminum props that we 19P but I'm not positive and I'm the 3rd owner so who knows what was put on it. Again no clue on the diameter.

I'd like to know what originally came on the vessel if possible and what I should really be running. My understanding is that I should be in the 4600 RPM range WOT and it has been suggested that I run a 17P SS but then some one started throwing diameter out at me.

I'm looking for the best overal all performance.

THANKS in advance!

David

 

[Silvertip]

Re: Celebrity 290 SC

Diameter is certainly a factor but it's not the main factor. Pitch is far more important than a slight diameter change. If the prop is not marked with diameter and pitch, measure from the center of the prop shaft to the tip of one blade. Multiply that number by two for the diameter. The prop should be 14-1/2 - 15 inches in diameter. Before messing with props make sure the hull is clean and the engine is in a proper state of tune. Then make some wide open throttle runs with an average load. If you can't get the engine running at 4600 rpm you have the wrong prop and need to decrease pitch. A drop of 1-inch of pitch will raise engine rpm 200 - 250 rpm. So going from a 21 to a 19 would raise rpm about 400 - 500 rpm which would put you in the ballpark and help getting the boat out of the hole. You do need to know that a 19P prop from vendor "A" may not perform as well as a 19P prop from vendor "B" and vice versa. If you are getting the idea prop selection is a crap shoot, you would be correct. But with a little thought you can at least get in the ballpark.