Another prop question

[fishingman220]

I have a 5.7 mercruiser with a bravo one, on a 96 Pro Line cuddy fish. it weighs about 3500 to 3800. When at WOT it runs about 40-42 and revs about 52-5300. the cover on the motor says wot should be about 46-4800. The prop is 14.3x19 i think, i know its 19 pitch. should i go up to a 21 pitch? or even a 23? also how much would i gain on top end? and would i loose any bottom end? Please help, i dont want to over rev the motor and blow it.

 

[rndn]

Re: Another prop question

Changing pitch in a prop usually results in a 200 rpm's net change for every 1 inch of pitch.

 

[K.P.]

Re: Another prop question

First I should clarify all of my boating and propping experience is with outboard motors, not inboards or I/O's. So I don't really know what your RPM's should be. However, the effects of changing prop pitch and diameter is typically consistent in therory but not consistent from one manufacturer to another, within the same manufacturer, nor one material type to another.

Changing from the 19 to the 21 should put you into the top end of theMax WOT RPM range you provided and eliminate or minimize the chance of over reving the motor. You will loose a little hole shot but I don't think it will be much at all. You should gain a couple MPH top end speed and experience better cruising speed. Going up to a 23 pitch will reduce your hole shot considerably from the 19 pitch but still should keep your motor operating within the MAX WOT RPM range and eliminate the risk of over rev. You'll also get considerably more MPH over the 19 (maybe 5 or 6 MPH) but may experience some porpoising if the 23 doesn't quite get you into the RPM range or in the low end of the range.

For the most consistent result, try to stay within the same brand of and model prop, and approximately the same diameter.

I'm sure others with better knowledge of your rig will have better info.

 

[fishingman220]

Re: Another prop question

thank you very much, that helps me alot. I have a mercury vengence prop, should i stay with same brand and model just change pitch?

 

[Tail_Gunner]

Re: Another prop question

thank you very much, that helps me alot. I have a mercury vengence prop, should i stay with same brand and model just change pitch?

Props can be expensevie..Id check you tach to verify it's true. They have proven to very ...umm all over the place and your trying to chase down a very narrow range