Propeller help...so frustrating.
 

Okay, I have researched and researched, getting one contradiction after another, from Mercury's website to forums. So, I am going to try this here.

I have a Baja Outlaw 20 with a 383 performance stroker pushing 350+ hp hooked up to an alpha 1.

Currently, I am running a Mercury Fury 13.5 x 21 pitch propeller, which I am sure is totally the wrong one. At 3000 rpm's I am running 35 mph. At 5000 rpm's I am running about 56 mph. I have no rev limiter, which is why I am trying to find a propeller that will increase my speed and decrease my rpm's so my motor doesn't go boom.

Mercury's website stated to run a Laser II 23 pitch, where it then states that the Laser II's are for low hp motors???? Of course, there were some other recommendations.

At this point, I have been told by a reputable propeller shop here in Houston to run a Bravo I 24 pitch. What are your experiences and thoughts on this? Any info would be great. Thanks...

The bravo 1 4 blade you will come out of the hole better and like the ride . The bravo1 is 14.5 width and is a bigger than you blade you have. If your looking for bow lift ( you are ) try a solas titan hr 25 it has a lot of rack and lifts the bow

looking at http://www.mercuryracing.com/propell...sterndrive.php

it seems that the bravo I has a 15 1/4 in. diameter. will that fit? i will measure it when i get home to double check...

i have been recommended today by a prop shop to try the bravo I 15 1/4 by 24, which they claim will fit no problem at all...what a headache...rrrrr.

A smaller dia. prop should be able to carry your boat. The bravo can run on the alpha. Do the prop shop you are referring to, have a test program? The Revolution 4 is a 14.625 dia. prop. On a 20 footer that should be enough. If your drive is deep, a Mirage or LaserII should be the fastest. I ran an 20 Outlaw last year with a 23" mirage, and that worked well. Boat had a 454. Don't remember if it was a 310 hp or a 385 hp. Measure your x-dim. that will make it easier for us.

Hope this helps.

Yup,

23 Mirage, or Mirage Plus would be my first try.

i will get some dimensions when i get home. i honestly believe that a 23p will be too small given the number of rpm's i can carry at wot. literally, i can turn that motor over till the cows come home if i wanted, which is what i don't want to do...the guy i bought it from did some serious work to the motor, so i know it will do what it needs to. i just don't want to blow that alpha drive out turning too many rpm's.

i have looked into the mirage plus props but will have to go with a 25p given they only increment by 2. i am afraid that might be too much pitch....the place i contacted is a professional place where they do custom work on propellers, etc.

Ratio?

See if you can get your hands on test props. I tested 4 props before buying. Guessing will get pricey

Thanks guys im going with the bravo 1 15.25 x 24 the diameter will fit and i know having the four blades will help with lift. Thanks for all your help. For all that believe a 23 is the best bet, it is only 2 inches up from what i have now and i need to knock off about 1000 rpms. Im not running the typical outlaw 20 motor either.

Remember that the Bravo 24" is not a true 24", more like a 22"-23". Is your wot rpm's 5000 now, or is that what you want after dropping a 1000 rpm's off? 4000 rpm's is not much for that engine. The merc 350 and 377 likes to be @ 5000-5100 for wot.

Good luck with the B1. Keep us posted.

Was the motor dynoed when he built it? If so, look at the powerband to see where max HP is made and prop to that. I would not go with the Bravo One. Its diameter is more than you need to carry the bow of that boat and you'll be trying to spin more prop than you need... which will rob top end.

The smaller V-hulls like yours really like three blades for top end speed. They may slip or even blow out a little coming on plane, but I'd welcome that if you're running 350HP through an Alpha.

I think the Mirage suggestions were spot on. If the 23 is too small, try a 25, or a 27, or a 29, or whatever it takes. That's going to be your best bet for top end and not trashing your drive.

I contacted the guy who built it and he said it is actually pushing about 400 horsepower..it has roller assembly, cam, summit racing aluminum heads, msd ignition, high compression pistons, etc. At this point i am torn between the bravo 1 24p or the mirage plus 25p. I agree on the diameter being a bit large on the bravo 1 and usually use my trim tabs to plane and reset from there when cruising.

According to the mercury racing website, they rate the mirage plus at 50+ mph and the bravo 1 at 60+. Honestly, i feel this setup on the motor i have will easily do 65+ while lowering rpms. With that said, would a 25p mirage cause too much slippage........?

What about a revolution 4 14 5/8 x 25...? That would give me the lift and possibly lower rpms while increasing top end a bit...

Stop in your tracks and call Brett @ BBlades. Not only will he eventually nail it down, he's the only guy I know renting props to keep you from buying and trying an endless array of possibilities.

Otherwise, you're throwing darts at a wall; in the dark; using the wrong hand; standing outside where there may not even be a wall; and the wind just started blowing...

And make sure you have an accurate means of monitoring RPM. Gauges suck for what you're doing.

One prop I would suggest is a 24p Turbo 3 blade. When I had my 272 with a 502 efi I ran a mirage 23p and it ran 65 mph. I went to the 24 turbo and picked up 2 mph. The turbo was a little slower to get on plane but not much. I did have a bravo drive so I don't know it would work on an alpha.


If you are concerned about the alpha drive I can hook you up with a complete Bravo transom assy. if you decide to go to a bravo setup.

I will make a few more phone calls monday. I appreciate all of your insights an information...just damn frustrating. At bblades, do you happen to have a ballpark on the cost of renting a prop and do they ship it, etc...?

SDFever is right, get Bblades to help with the test props.

If you want to run 4 blades, go with the rev 4. You don't need that big a dia. on that short hull. It WILL slow you down big time. If you could push 70+ mph, the mirage 25 will be bang on, unless you need 5200+ rpms.

I have ordered the standard mirage plus 23. I am expecting it in next week and will post numbers with it. This week, I am going to GPS the 13.5 x 21 pos Laser II I have on there now and see what the difference in gain is.

Gear ratio 1.5 WOT 6000+ HP 350+

As was asked earlier, was the motor dynoed? If so what rpm are you trying to prop it at? If you are truly trying to lower your rpm by 1000 rpm I think you may be jumping the gun on buying the 23 mirage plus.

Well, I have had 2 good questions...

Was the motor dynoed? I am under the impression it was not. Simply giving myself a rough estimate based on the major upgrades done to the motor alone.

Am I truly hitting 6000 rpms? Meaning is my tach 100% accurate? Well, they look like the same gauges from 15 years ago. Not to mention, I am turning an alpha 1, not a bravo 1, which is rated for the 270hp motors.

Balls out, I would go with a 25 and up, and turn it like crazy. However, I am trying not to do the bravo 1 upgrade this season, if you know what I mean.

Going up 1 inch in diameter in prop will reduce rpms and going up to a 25 pitch from a 21 will reduce them approximately 700 to 800 rpms. What a mind game.....

Keep in mind that RPM's isn't what breaks drives. Torque and more importantly rapid changes in torque (i.e. jumping a wake or throwing the juice to it out of the hole) is what breaks drives. If you prop your engine wrong you may be lugging it which is bad for the engine. You may also prop it to where you're running at the peak of the torque band all of the time. Also bad in my opinion. Once again, a dyno run would be best if you want to get the most out of the rig. Short of that, pick a WOT RPM that you think is right or you're willing to run at and test. Just buying props and trying them is a bad and expensive idea.

Ok guys, I understand what you guys are saying. Keep in mind I have purchased one prop. I am not going through one prop after the other. Several people have made several suggestions, and unfortunately, only a couple or maybe even one can be applied at a time. I need a good baseline given what I ran last year was crap. This is a 20 outlaw that is our family boat, not an MTI looking to run to Cuba in no time. Keep the suggestions coming....

If you don't like the outcome with the 23 M+, call us. My partner and I have 30 years experience in the prop world employed Mercury Marine and Mercury Racing and a combined 50 years experience including our staff.

We will save you the guess work and we loan props for $45. We have Mercury, Turbo and Hydromotive props to test for your hull.

Brett

prop follow up
 

Here is what I got with the 23 M+:

Cruising speed was awesome. I can hold 3000 rpms and obtain about 40mph, when the water isn't an ocean on the lake.

Top end is a whole different story. I am glad I went with the 23 not anything larger. It lowered my rpms to 4800 at wot, which is what I needed. At wot, I am running right at 58 on the GPS, which to be quite honest, is okay, given I only bought the boat for 7500 cash and will be upgrading to a 23+ footer in the next few seasons.

Overall, was looking to get a bit faster at top end, but will take the cruising rpms anyway.

Now, if I had some bad to the bone rig, as most of you guys do, then I would be concerned...I appreciate all of your guys' help on here. Great information led me to get what I am happy with. Thanks.

Why only spin at 4800rpms???? Get the prop labbed and spin it up to 5000-5100rpms. You'll pick up a couple mph.

I just put a 383 in my 18 donzi with 400+ HP.i HAD A 23P ALSO ran to high in the rpm but fast.So i bought a 25 labbed mirage plus which is great.Brought the rpm down into 5500rpm running high 70to low80.my alpha is a1;50 ratio with a drive shower on it no problems.i have the prop for sale if you are interested.I dont need it anymore for i put on a blackhawk drive and new props.

Did some timing adjustments and ran 67 memorial day weekend on Lake Livingston...23 mirage worked perfectly. Again, thanks for the advice.

Glad to hear things are coming together. Part of the reason the mirage plus reduced your rpms so much was the diameter over your other prop. If you lab the 23 you should get 2 mph and get your rpms more where they need to be. Just remember your cruise rpms will be higher as well. I dont think it will be any harder to get out of the water.

Yeah, it is a much bigger prop. I have started to fine tune my distributor by finding the sweet spot and found it last week. I realized it was a little advanced and now can get right at 5000 rpms at 67 with the wife going crazy....the 20 loves to chime and is a crazy ride at that speed. I blow out when taking off but man when I get on plane and trim up, it hooks up nicely.

The one thing that gets me on some of these postings, and maybe I am naive to a certain extent, is how someone with a big block cant turn a 23 and up prop and get some decent speed above 75 mph. I understand power to weight ratios and drive ratios....a lot of theoretical contributions in these forums and would love to see some real follow ups, not, "I have this and did 100 mph in a Baja type stuff." A 496 ci in 2 boats that have simar weights and simar hulls and similar drive ratios should realistically run the same with the same prop....????

Just a suggestion that has worked for me over the years on quite a few boats...call Bob Teague in Valencia Calif. Bob is a great guy who always has time to help.
Good luck.

I know now I have the right setup. Thanks for all the replies and info!