Should I change my prop pitch?

[cobra 3.0]

I presently have a 13 3/8 x 17" pitch prop on my open deck 16' Peterborough boat with OMC Cobra 3.0 engine. It goes 36 mph at close to 5000 rpm with two kids and myself(450lbs.) in the boat. <br /><br />If I go to a 19" prop, what increase in speed can I get if any? Will a stainless prop in 19" get me even more speed? What stainless model is best for general boating and tubing with kids?<br /><br />Also, I heard putting holes in the blade of the prop helps too...is this a bunch of bunk?

 

[tylerin]

Re: Should I change my prop pitch?

If you go to a 19 you will loose low end and may be more difficult to plane. They have props w/ holes in them but the manufacturers know exactly where to put them I assume. I use aluminum props myself because if I hit something (and I have) I've got a better chance of just having to replace my prop and not something more costly then w/ a ss prop. Just my opinions, take it w/ a grain of salt.

 

[DJ]

Re: Should I change my prop pitch?

Cobra,<br /><br />I believe the maximum wide open throttle rpm for that engine is 4600 rpm.<br /><br />A 19" will drop your rpm down the recommended. You may gain a mph or two. A stainless may help for another 1 or 2.

 

[magster65]

Re: Should I change my prop pitch?

I'd go for the 19" prop but definately keep your 17". At 5000 rpm w.o.t. it must have a great holeshot for skiing or boarding...

 

[chris in va]

Re: Should I change my prop pitch?

I recently took a brand-new Sea Ray 17' bowrider out on a lake with the 3.0. No matter what I did, we never got over 34mph GPS indicated. That 4 cylinder just doesn't have a lot of guts...

 

[Tufan]

Re: Should I change my prop pitch?

Increasing the pitch wont necessarily give you better speed. Increase the size (diameter), decrease the pitch.

 

[bluewater19]

Re: Should I change my prop pitch?

I would look at a 19pitch laserII. It is a great bow lifter and will put your motor right in the sweet spot. If money is a problem look on ebay. A 18 pitch 4 blade alpha one aluminum prop would also be a good choice.<br />Good luck!!

 

[Bob_VT]

Re: Should I change my prop pitch?

First try to maintain a prop to keep your engine within RPM range.<br /><br />As for the holes.... they are in the hub do a search for it that has been discussed here before... it permits slippage on your holeshot by venting exhaust gases across the blade surface.<br /><br />Bob

 

[jka]

Re: Should I change my prop pitch?

I'd agree with tylerin and dj. you may gain a little. but frankly a ss isn't worth a couple mph considering the cost and damage it'll do when you hit a rock.

 

[Rockyncali]

Re: Should I change my prop pitch?

Pitch degree has always interested me. I don't really care about top end since all I do with my boat is wakeboard. Right now (before outdrive damage) my boat would top out at about 34 mph at about 4500 rpm with a mercruiser 120 hp 4 cyl. I think that's more than fast for me but I would like a better hole shot. You know, to pull out boarders faster. I would even give up some top end. Since I spend most my time at about 25 mph. I heard SS prop pros and cons but what I heard that I liked is that they provide an awsome hole shot. True or no?

 

[achris]

Re: Should I change my prop pitch?

Awesome holeshot? Laser II. End story! I put one on my 2 ton cabin cruiser, punched the throttle and thought someone had strapped on a Saturn V rocket engine!