Correct prop??????

[Eddie Ray]

Trying to find the right prop for my boat.
It is a 21 ft trophy hardtop 1985. It has the aq125a motor with the 270 outdrive .
The number on the transom is bl2008fd0585.
The prop says 15L17,and the number is 814612.
The top speed is about twenty ,with the RPMs at about 3200. Both should be higher,and that is my problem. Have done all of the low rpm test and stuff,now wondering if I need to change the prop?
Any info,and help would be great.
Thanks a lot
Eddie Ray

 

[steelespike]

Re: Correct prop??????

As usual I have no info for an 85 Volvo.
You'll have to help out with the displacement,hp,max rpm rating,and the gear ratio.
Ratio is usually stamped on the outdrive.I'm assuming the hp is 125 but not necessarily.
If your motor is rated at 4800 you need to make up 1600 rpm and that would require about a 8" reduction in pitch.Puts you in the range of pontoon or houseboat props.A 17' prop is very likely close to normal.You might varify the tach is accurate and get your speed by gps.