Upgrading to a 19P Prop From a 17p to Bump Up My Crusing Speed at 3000 rpm???

[Alex_AGB]

I wanted to get your guys? opinions on switching to a 19p from a 17p prop to get my cruising speed up closer to the 30mph mark while keeping my rpms at or below 3000. As well as opinions on going with a 4 or 5 fin 17p prop.

Here?s what I have?
.2000 Sea Ray 230 Overnighter. (Clamed dry weight 4000 lbs plus the 750-1000+ pounds of gear and fuel)
.Merc 260hp 350TBI
.Alpha 1 with 1.47r ratio
.Vengeance 17P stainless prop

My self and another passenger (450 pounds) at 26mph I?m turning 3000rpm and maxed out at 48-49 mph I?m turning 4900rpm

95% of my time while moving is spent at 3000rpm because that?s where I get the best mileage. Thanks!

 

[jestor68]

Re: Upgrading to a 19P Prop From a 17p to Bump Up My Crusing Speed at 3000 rpm???

Since you are turning over your rpm limit(4800) now, you can certainly move up to a 19 Pitch.

That would lower your WOT rpm to about 4500-4600 rpm and pick up 3-4 mph at cruise speed. I would stick with the same style of prop for more predictable results.

 

[Chris1956]

Re: Upgrading to a 19P Prop From a 17p to Bump Up My Crusing Speed at 3000 rpm???

So you are doing 26 MPH at 3K RPM and then your efficiency gets better at WOT, where you are doing 49 MPH at 4900 RPM. I suspect an error in your speedo or Tachometer. If the tach is correct, at WOT I would expect no more than 44MPH, likely a bit less. 49MPH is very good for that setup, actually a bit too good.

 

[steelespike]

Re: Upgrading to a 19P Prop From a 17p to Bump Up My Crusing Speed at 3000 rpm???

I wonder what the throttle position would be at 3000 with a 19" prop. Hole shot will likely take more time,it may be more sensitive to added weight.

 

[steelespike]

Re: Upgrading to a 19P Prop From a 17p to Bump Up My Crusing Speed at 3000 rpm???

So you are doing 26 MPH at 3K RPM and then your efficiency gets better at WOT, where you are doing 49 MPH at 4900 RPM. I suspect an error in your speedo or Tachometer. If the tach is correct, at WOT I would expect no more than 44MPH, likely a bit less. 49MPH is very good for that setup, actually a bit too good.

Prop slip seems a little optimistic for a boat that size at 8%. @ 4900 and 49 mph.

 

[Alex_AGB]

Re: Upgrading to a 19P Prop From a 17p to Bump Up My Crusing Speed at 3000 rpm???

Thanks for the input guys! I've decided to get a 19p prop but I also want your opinion on which one is the best! I've done some light searching and right now a 19p Merc Enertia prop is what I'm leaning towards... Opinions please! :joyous: