bajaboy217

Here is a little refresh.... I have a 01 baja 25 OL Bravo 1, when I bought the boat in 2010 it had a 7.4 mpi (310) hp with a 21p mirage+ and got gps speed of 55, I ran that for a litttle while and was not happy with the speed so then I put a 5psi procharger on it. With the procharger and a larger prop 24p bravo I was able to get my speed up to 64 gps. I ran the boat with the procharger for most of the 2011 season without a problem. At the end of the season I started having problems with the motor, it started to backfire and was making some cool noises on the top end, and my oil was turning a little milkey. At that point I was just glad the season was over and I had the winter to do a repower. At first my thought was to put a hp500 in it and call it good but after posting here on the board many people said you are better off going with a 454 or 502 mag mpi.
I purchased a 502 mag mpi off a friend of mine that was bored .30 over with srp pistons and a crane 731 cam and crane gold roller rockers, and a ecm tune. I put a set of emi thunder exhaust on it and bolted it in. I took it out to play last weekend and got a gps reading of 71.3 @ 5200 rpm before I ran out of room on the small lake I was testing on. I was also running with the same 24p bravo prop. With a little more room on the lake and some more trim I think I can get a bit more out of it. I was told that with the ecm tune the rev limiter was set to 5500-5600 rpm.... I have not confirmed that yet but a 5200 there was no sign of any rev limiter.
So far its looking and sounding good, can't wait to get back out there!!
As for the 7.4 mpi I haven't torn it down yet to see what went bad but thats on the to do list....

A.O. Razor

Congrats on the new motor Sounds like you're pretty well dialed in there. 7% slip, nice You can always throw a labbed 25" Mirage+ on and see what the big number is

bajaboy217

Razor, in a previous tread you mentioned a revolution 4 prop for bow lift do you think that would help me at all with my current setup? On my previous setup with the procharger I tried the 25p mirage+ it was faster than the 24p bravo but, I found it hard to keep it hooked up. With the bravo I had no problems .

Baja_man

7% slip is incredibly, you could try a few different props but i can say that trying to duplicate the 7% will not be easy. Was the bravo 1 labbed? If not, there should be something gain by labbing it. If you want to keep the props un labbed the Rev 4 does give some additional bow lift over a bravo 1.

bajaboy217

No, the bravo was not labbed.
How do you calculate the slip%? How does that work the lower the number the better?
Before I go messing with the props I want to take it out on a larger body of water where I have plenty of room to run and play with the trim so I can see if I can get anymore rpm and speed out of it.

blaquebaja

I also have a 25 OL keep all info coming. I have 454 bored 030 top speed with Ballistic 25p prop was 65mph. I`m in the process of building 540. what type steering do you have?

bajaboy217

Nice, that boat should be a little rocket with a 540!
As for the steering right now I am running bone stock, but because I am running a bit faster now I am thinking about adding one of imco's single ram systems to it. I dont want to spend the money to go full hydro because I dont plan on keeping the boat much longer. Imco's single ram system new is about $1400. At this point I think most people would agree that I need to do something with the steering.

A.O. Razor

It kinda depends on what you want. In stock form, the B1 lacks bow lift, BUT as a lab prop, the B1 it's superior to the Rev4 and will offer better top speed, cruise efficiency and it can be labbed for the needed bow lift. As mentioned, your slip is incredibly low, so that's pretty good for any stock prop. However if you feel you have a problem with bow lift and want to run a stock prop, yes for a 4 blade, the Rev4 is the answer. Normally I'd say you would gain speed, but seeing your slip is what it is, not as sure as I would normally be. Freeing up the bow, ie. reducing vetted surface is the key to speed. If you can borrow one in either 23" or 25", give it a try for sure. All this being said, I'm sure your boat will handle better and 75% sure it will be a bit faster with a Rev4. The first to try, is a 23". If you decide to lab your B1, TRY ANOTHER STOCK 24 B1 FIRST and see if you can duplicate the result. If yes, lab what you have, if not, read on. Stock props are like hulls and motors. Sometimes a really great one sees the light of day and imo, it's better to mess with a normal or "average" prop, so to speak. Don't forget that labbed props are not as durable at stock props when they are thinned in the blades.

The easies way to calculate your slip is just to use one of the online offerings. Merc Racing has one, so does Hering and Bam. I put in a pitch of 23.3, your speed, drive ratio and rpms, it is as simple as that. Oh, and Hering has one as an app. That's the one I used. Way cool app.

If you ever decide to try for 75+, a labbed M+ 27" would be the prop, but it won't be a nice all around prop. It will need a light load and be slow out of the hole, but a lot of fun

A.O. Razor

You will want to run full hydraulic on that baby. IMCO, Hardin (Mayfair), Latham, Zeiger ect. are all good brands, you won't go wrong with either. Once you go full hyd. nothing else is good enough. As someone said in another thread today, there is no cons to full hydraulic steering. You don't want to swap ends at 85.

Sweet project, good luck with it.