THE RESULTS ARE IN!

[bryan275]

Well...

The Procharger has been installed for a while now and I have some test results.

Bone stock my boat ran 66-68 mph on the speedo. I confirmed it to run 4 mph fast with gps later. I tested with 1/2 tank of fuel, no water on board, 2 people, gear including a full cooler;) , and the stock 23 mirage plus prop. The air temp was 77 and the water temp was cold with light chop.

Now at 3.5lbs of boost, I have a gps best of 72.3 mph. The speedo reads an optimistic 76 mph. I consistantly run 71.3 to 71.8 mph all day long in the same conditions (except for mid 80's air temp and warmer water). I am now running with a stock 28 Bravo I four blade at only 4550-4600 rpm.

I really need to lab finish the prop to get the rpms back up to 4850-4900 and pick up some more speed. I think I can get 75mph after lab finishing based on these calculations:

Stock -- (23 pitch X 4900 = 112700) / (1.5 ratio X 1056 = 1584) = 71 mph Theoretical Speed
(71 mph theo - 64 mph actual) / 64 actual = 11% Slip

Procharged -- (28 X 4550 = 127400) / 1584 = 80 mph Theo.
(80 mph theo - 72 mph actual) / 72 = 11% Slip

Lab finished -- (28 X 4850 = 135800) / 1584 = 86 mph Theo.
86 mph with 11% slip = 76 mph actual!:evil

I have run into some more unforseen problems that have delayed getting these results sooner, but I'll save these details for another post!

Bryan

[TeamBajaMarine]

Bryan,
Please tell us about your motor, what model, HP and what you did to your motor prior to procharging.

[bryan275]

Sorry Blake, I took for granted that everybody already knew!

2003 Baja 275 - 496HO 425HP Stock- Bravo X - Latham Full Hydraulic steering - Removed Corsa Mufflers Prior to all testing.

There is one thing I would like to mention to all that may be dissapointed with the intial speed numbers on the stock motor. I found out -after- the procharger install that my "computer" may need to be recalibrated due to "MINOR" adjustments needed to fuel delivery timing causing the engine to run overly rich especially at speed. Mercruiser sent us a new computer and it helped. You can imagine that with the engine running too rich at stock and then bumping fuel pressure up to 62lbs what happened!:eek

I'm not sure how much effect it would have had, especially since Mercruiser said it was only "minor adjustments". Getting technical info from them, especially concerning the programming, is like pulling teeth!

I will say that old computer vs. new = cleaner transom & smoother idle with the procharger.

Bryan

[Steve Chalupka]

B -
I know you sent me a private email, however, I'll answer it here. My 28" Bravo I is not labbed. Not a smart move where I boat (lots of shallow water here on the Chain of Lakes,IL). I tried a 30", but sacrificed some minor holeshot performance. The 28" I now have on runs around 5000 -5100. Right where I want to be. The 28" makes for a better "all around" prop. Good for the entire season, especially when the temps climb. The reason I attain speed of between 78-80 mph is because my motor, prior to the installation of the Procharger was professionally built, balanced and blueprinted.
A couple of weekends ago I ran (no kidding - you can ask all the passengers on the boat) a solid 74 mph. This was with 4 adults, 2 children and approx 30 gals of gas! I couldn't even believe it. When my mechanic and I took my boat out a few weeks ago we noticed that my speedo ran within 1-2 mph of the hand held gps unit we had on board. I'm happy!
Over the winter I'm putting on a windscreen, external steering and possibly new manifolds.

[bryan275]

Cool Steve!

I'm sure that all the work you put into that motor helps a lot. I'm glad to hear your numbers, it's hard to compare results I get with other engine applications, or hulls. This winter I have some projects planned for the boat in the powerplant dept. It's kinda like a rash, it spreads when you scratch it!:lol

I'd like to meet you sometime maybe in Chicago on Lake Michigan!

[DCH1]

Thanks for the results. This stuff is of great interest to me, and I assume others also.

DCH

[Baja Daze]

Great Results! Thanks for the update. This is perfect information; very interesting.

[rayboss]

Bryan,i too am a 03 baja 275 owner of 5 weeks only have 15 hrs on GET LOW .have a 496 mag 375 hp,great to see all you have done,in the near future i plan on up grades also have not decided on what to do but your project has inspired me.I live in jacksonville florida run off shore alot.i plan on getting my prop done soon,my son runs a speed shop and has several outlaw\series cars,he wants to go crazy w/ it,,,,i dont know,,i will let you know what we do.,,,,,,archie

[DaveH]

Nice uptick in speed. I had the computer done on mine as well. I have just passed the 12 hour mark on my boat (finally some good weather) so I will begin doing some speed tests the next time I am up to the lake. I will have to tread easy until 20 hours but should be able to do the tests since top speed will only be held for a minute or so.
I should be able to compare to your stock numbers and to be honest, am hoping for ~66 once fully broken in. I am not sure where the rev limiter is set (5100 or 5150) but I know
that 4800-5000 should be about right. I have not been above the 4500 mark yet and only for very short time frames, but have seen 65 on the speedo at that rev. with moderate load
(similar to your test). I will GPS when I do the speed trials (I do know that the speedo is "generous" by at least 3 MPH. Hope to lab a prop next. I want to go Whipple, as you know, but could have a challenge with the wife on that one.
Looks like Steve has his dialed in sweet. I think you will definitely cross the 75 barrier after some minor changes. Did you choose the 28 based on Steve's input or some other recommendation? Seems like a huge jump from a 23 (could have sworn I had a 25, will recheck). Were your numbers pre or post the computer change with the ProCharger??

Dave

[DaveH]

One other thought. Would the lab finishing possibly reduce the slip value by a percent or two? Not sure if there is a gain in that area or not based on the additional cupping etc.

Dave

[DCH1]

DaveH:

I think you'll find that lab finishing does exactly that. But not the same amount in every circumstance!

DCH

[bryan275]

I'm not sure if lab finishing will reduce slip or not, hopefully Darrin will chime in on that one.

As far as the tests with the new computer, I tested the Procharger with both computers and the results I posted are with the new one. There was almost 2mph difference old program vs. new!

I chose the 28 pitch prop AFTER first trying a 26 pitch. The stock 26 ran at redline. I don't want a boat with a bunch of time on the rev limiter. Here's how I calculated it:
(26 pitch x 5000 rpm) / (1.5 gear x 1056) = 82 mph theo speed
82 mph x 11% slip = 73 mph actual with no room to improve due to rev limit.

I guess if I was always running heavy and wasn't going to lab finish the prop, I would run the 26 pitch.

[DCH1]

Bryan:

I agree with you. You're better off running 4500 to 4800 RPM WOT than 5100 RPM WOT for the long-term health of your motor. And your math is correct. You get 73 MPH with 11% slip and 1.5:1 gearing. The ultimate question is, can you improve much on your slip at 5000 RPM? It seems within the range of the possible for your powerplant in a deep vee hull.

I've heard guys say that they believe they get high single-digit slip values at WOT. I suppose that is possible also, but it hasn't been my experience. Then again, I have always run a deep vee type hull. Just for fun, I took the test results on my 342 as published by Boattest (yes, I know, the tests ALWAYS seem better that what WE get). Best slip was 12% at 65 MPH and 4500 RPM. Slip increased slightly at 5000 RPM to 13.5% and 71 MPH. Stock boat though, and your planing surface should be smaller at your higher HP as you'll be a bit more out of the water.

Why don't you give Daren a call and talk it out with him? He may not be reading this thread in the General Forum. I think he can do some things to either prop that will "tune in" your RPMs. My call would probably be the 28P, but Daren will know better.

And thanks again for the results. It is really good to see someone actually do this stuff and really sort it out.

DCH

[DaveH]

I agree with both of you that allowing a bit of headroom is a good idea though I know that there are kits out there that take advantage of slightly higher RPM (up to say 5400 or so) though they require the uptick to premium (91 oct)gas as well. I would have thought that a three blade would also give you a mile or two per hour over the four blade (though the holeshot might be slightly less). I got a kick out of DCH's assessment of Boattest being slightly more enthusiastic on top speeds. If you look at the test for the 275 I believe the top speed was somewhere around 61.7 with the 496HO. I was so shocked at this value that I wrote to them and asked if they were actually testing with the 496 Mag. They answered that different tests will yield different results or something to that effect. The weird thing is that Boating mag. came up with a top speed of 62.7 supposedly with the 496HO and Powerboat had 63.x supposedly wih a 496Mag so go figure. I sure am hoping for, and expect something >= to 64-66 top end with the HO and know for sure that I can get 61.5 gps without hitting WOT.
Ditto on the test results, these really help give a sense of "reality" to our top end expectations. One other question for Bryan, was there any chine walk issues at top speed or did you still feel like there was solid control of the boat?

Dave

[bryan275]

Thanks for the comments/compliments guys!

I have considered and am currently looking for a "modified" computer program or "kit" so to speak to compliment the Procharger, but to no avail. I am not aware of one yet. I am not comfortable raising my rev limiter much beyond the factory setting, due to the fact that my engines internals are bone stock.

Dave - I am already required to run 91 octane with the Procharger to avoid detonation. As far as the 3 Blade, you are probably correct about the top speed. The best thing about the 4 blade I have found is the handling. I have purposely tried to "blowout" that prop with hard lock to lock turns, high speed turns, and even swamping the back end, but can't!

As far as chine walk... it's there, but very minimal up to wot. (Keep in mind that I am only running at 72mph, not 75-80 yet!) Funny thing, on glass the boat seems to chine walk MORE than in slight chop and run slower. I think it is due to the fact that the chop tends to aerate the hull.

I have a theory on the boat test results. They are testing in high humidity, and each boat, engine, and test conditions are different. It's also interesting that they tested the 25 outlaw, (arguementively nearly the same running surface as the 275 and similar weight), at 66mph.

I agree that there is some confusion as to which engine was tested. I remember reading the Powerboat Magazine article as to say, "baja chose a realtively mild, 375hp motor that will be the most popular power choice according to the Baja rep."
Maybe they sent a HO to Boattest, but not to Powerboat Mag?!

A tpyo is also possible, considering that on Baja's OWN web page detailing the specs for the 275 they have the deadrise listed as "21 deg" not 24.:b