Prop pitch question..again

[stunod]

Hi,<br />I have a 21' boat with a 470 merc 190 HP<br />At WOT, the engine sounds like a car in low gear. Also I feel that the boat is not as fast as it should be. <br />I found the outdrive manual and it said 3800 - 4200 rpms. When I looked at my tack at WOT,I got it up to 4700 rpms.<br />The prop (which I just bought) is a 15x17<br />Does anyone know what pitch I should get?<br />or what RPM i should try to keep it too?<br /><br />Thanks in advance,<br />Lou

 

[Mumblerone]

Re: Prop pitch question..again

You'll want to go up in pitch to get the rpm's down. At WOT you want the rpm's to be 4200. I assume it is the correct manual for the boat. Is it an outboard? Sounds like an I/O at that max. rpm. Might have to go to a 19" pitch or higher, possibly cupped. Hope this helps somewhat.

 

[Mumblerone]

Re: Prop pitch question..again

You'll want to go up in pitch to get the rpm's down. At WOT you want the rpm's to be 4200. I assume it is the correct manual for the boat. Sounds like an I/O at that max. rpm. Might have to go to a 19" pitch or higher, possibly cupped. Hope this helps somewhat.

 

[Hooty]

Re: Prop pitch question..again

As a rule of thumb, 1" pitch = 200rpm.<br /><br />c/6<br /><br />Hooty