Prop for Volvo 131aq

[Jesse8676]

I have a project / first boat that I got last summer. I did some work to her and now that it is on the water I am Thinking I could use a new prop... I feel some vibration and top speed is only 32 mph @3200 rpm. It is a 19 ft Bowrider with a Volvo 131aq. Have a 14 x 21 prop. I was told at a prop shop that I need a 14 x 17 for this engine. Will that make me lose top end speed. 32 mph is not all that fast to me.

 

[alldodge]

At 3200 rpm WOT your lugging your motor, which can damage it over time. Many people use a higher pitch prop trying to save fuel, but in the real world performance is lost and fuel usage goes up.

You need your rpm higher and a 17 would be a good start. The boat will come out of the water quicker, and you should not loose top end, you may actually gain some more

That said, make sure your tachometer is accurate

 

[Jesse8676]

Thanks for the information. I did have hard time getting it to plane but add hydro foil and that is no longer a problem. I will check the tach to make sure it is accurate.

 

[Jesse8676]

I got the 14 x 17 prop and boat WOT are now 5200. I have to back out of it and at ideal listed rpm of 4500 I hit 42 mph which I love. Had no idea 10 mph could make a big difference. Just a little worried about the high WOT range.

 

[alldodge]

Looks like you could use a 19 pitch, which should drop your WOT by 400 rpm.

That is if your not trimming up to much and ventilating the prop a tad