bravo 1 question

[JGIPSON]

I just got a 24'4" Vindicator, it has a 7.4 L mercruiser with a Bravo 1 outdrive. It has a SS 21 pitch Mirage prop. at WOT I am running 4600-4800 rpm, at about 50 MPH according to the gps. what kinda prop should I look into to to increase speed to the 57-62 range. I have no problem at all coming onto plane right now.

 

[WillyBWright]

Re: bravo 1 question

You don't need a different prop. You need a bigger motor. Increasing pitch will only lug the motor and you could actually lose speed. It sounds like it's propped at optimim already.

 

[JGIPSON]

Re: bravo 1 question

what if i dropped to a 20 pitch 4 blade prop.....ive never used a four blade before.

 

[WillyBWright]

Re: bravo 1 question

4-blades have more drag than 3-blades, so they typically go a bit slower. What they allow is higher mounting on the transom to reduce gearcase drag which is a lot more than prop blade drag. But that only works for outboards. You can't raise an outdrive on a transom (simply). Your Mirage is probably one of the fastest sterndrive prop options you'll find. Some might get you a few more mph, but none will give you ten all by themselves.

 

[QC]

Re: bravo 1 question

I will only add that most boats are actually faster propped toward the bottom of their WOT range, and you are slightly over. I would guess that your best bet for 1 or 2 MPH would be to run a 22 inch 3 blade. Yes, your hole shot will suffer.

 

[SuperNova]

Re: bravo 1 question

Big block engines produce more torque than horsepower. If you go up in prop size I don't think your holeshot will suffer as much as these guys think it will. As I said in your other thread, prop it til you cant spin it effectively then worry about more power. That is the best way to maximize the setup you currently have. Go to a 23" cleaver style prop. Look to some the high-performance forums for some real advice as to what your boat and motor are capable of. These guys pretty much only know stock-type setups and I sincerely believe they have limited experience with high-performance tuning. No offense meant and I hope none taken.
--
Stan

 

[JGIPSON]

Re: bravo 1 question

Thanks nova....I kinda agree with you...this is a high performance setup, just need a little fine tuning to get the high performance part, as it has only been run stock by an older couple. I was just looking to increase top end a little. THe boat is big...but is not that heavy in essence of big boats, I have been comparing them online all day. I have a buddy witha stock baja 232 islander, with the same engine and drive as mine, he runs a 25 pitch prop, not sure of the brand, but i have been with him hitting 70 mph. thats why i was shooting for low 60's, as mine is a foot longer and about 800 lbs heavier.

 

[SuperNova]

Re: bravo 1 question

I run an older Wellcraft Nova- 28 foot with twin 260's, I have stock type 19" stainless 3-blades and I just spin them to 5000 rpm. My brother in law has the exact same boat, but he's running 23" 3-blade cleavers. He's got me by 7 mph and he spins his to 5000 also. I just can't afford the cleavers right now. So i know that just because you're hitting the right top rpm, doesn't mean there is no room for improvement. The other thing like I said before is you got to make sure you trim it right when you're running fast. Bring the outdrive up until the wake gets nice and flat where it converges. You'll feel the boat pick up speed steadily. If you go too high, you'll hear it start cavitating. Sometimes if you hit the right "sweet spot" the boat will literally leap ahead and you'll pick up several mph very quickly. This is the point where you may over-rev it and need to prop more aggressively for. Just my experience, may not apply to all situations.
--
Stan