donzi matt

iTrader: (1)

I recently made some motor changes to my 1993 Crownline 225 bow rider with a 350 mag and Alpha 1 gen 2 with a 1.47 ratio. I am estimating between 320-340 hp now. I raised my WOT RPM by about 600 RPM's to 5000, which is ideal, but it takes quite a while to get there. The boat still doesn't accelerate as well as I would like. It currently has a 3 blade stainless, with no markings to indicate size. Running through a prop calculator, and ASSUMING a 20% slip at WOT, it works out that it is a 21 pitch prop. I suspect it is a rebuilt propeller of some sort. This prop came on the boat but was not the original, but swapped on as part of the deal with the marina, so I know it is not what came from Crownline, but what achieved RPM that the marina had in stock. In short, it is sort of a mystery prop to me.

I am considering going to a 4 blade to help with the holeshot, but I am really hoping an optimized prop will not sacrifice top end. The boat feels like it runs wet, and I can't seem to trim it out enough to lift the bow with the current prop. I am hoping for some suggestions on what will work well. It is a pretty wide, heavy boat, and truth be told it would probably be more well suited with a big block and a bravo, but this is what I have to work with. Some suggestions would be great, as this is total black magic to me. Thanks in advance for any advice!

The specs right now are:

350 with vortec heads, comp xm-270-hr cam, holley 600 double pumper carb, silent choice open.
4900-5000 RPM
54mph GPS steady at that RPM, light chop

johnfharding

I would go with a 19 p. Rev4 in a four blade to start with. I think your boat is fairly heavy and the one I was in with the same set up I think was running a 21p Mirage. Good boat really nice and a Sharp looked all fire engine red with white interior. Try to find someone with a known prop model and pitch and post back with load , weather , conditions and some rpm and speed numbers and these guys will be able to help more . At this point we are all going to be shooting in the dark.

bobl

I've set up quite a few 225 Crownlines. With the Alpha drive the Rev 4 is a bit large in diameter. I'd run something like the Merc Vensura series in a 4 blade. The Vengence works good in a 3 blade. Also the Michigan Ballistic performs very well on that boat. Probably end up with a 19" pitch. Speed in the mid 50's sounds about right for your setup.

Bob Lloyd
Full Throttle Marine

A.O. Razor

Sorry for the hijack.

Bob

I've never seen the Vengance as a performance prop. What makes the Crownline and the Vengance work so well together? I've always seen, and used Mirages/M+ and LaserII's in similar 3 blade applications, but haven't had much luck with the Vengance(the few times I've tried). Why not the LaserII and M+ on the Crownline? Just curious.

Ps. I have been in a 19' and 21' boat with the Vensura. That is a nice four blade for sure. A surprisingly fast four blade.

bbladesprops

I just thought I'd through out some history.
Vensura was the original large hub Trophy (pre Plus).... Remember that? Boy do I.............. and the repercussions.

Then it was the ? Who can answer that question?

Now it is the Vensura.

I'll tell you more if you can get the second question correct.

The Vengeance is a nicely named QS thicker with HiPolish finish.
I kind of like the Rev4 too (depending on your goals). Down pitch to get your engine to the top of the R range for the engine. This will not hurt the drive and give the boat all around performance.

Brett

A.O. Razor

That was called the Offshore. Sometimes the Vensura is still called the Offshore series. What do I get

Racerryan

Hi guys: Just giving some background info on the setup we have on our hammer. Hopefully it will give you some help on selecting a prop.
'21, 3700lbs, 454mag mpi, 1.5 gear

original on boat 23" mirage plus 70mph on rev limiter (5150rpm I think) very good hole shot, bad cruise rpm.

bravo 1 24" stock, 68mph @ 4900rpm, good hole shot, very good cruise rpm and very smooth, never slipped.

bravo 1 24" labbed, 70mph @ 5100rpm, good hole shot, good cruise rpm and very smooth, some slip if trimmed up too much.

25" mirage plus, 70mph @ 4700rpm, slow hole shot, very very good cruise rpm, no slip.

25" mirage plus labbed, 72mph @ 4900rpm, not to bad hole shot, very good cruise rpm, some slip if trimmed up too much.

slip numbers were always between 6% and 9%. I do not think that your slip would be anywhere near 20%.

with the mirage plus props they also have the vent holes that help getting out of the water. I would start with a 19" mirage plus and take it from there. b blades can add or remove cup depending on whats happing with the boat. Good Luck!

donzi matt

iTrader: (1)

So I went and tried the Rev 4 19 pitch, and frankly I wasn't terribly impressed in my particular application. The prop bites hard for sure, but right out of the hole the boat lugs a bit till about 2000 RPM and then it pulls well. The holeshot was better, but not by much over my current 3 blade (which I confirmed is a Stiletto 21 pitch). I think a couple of things are at play here. One, the slip of my 3 blade gets the boat to build some revs out of the hole. And two, the hard bite of the Rev 4 keeps the motor from getting into the sweet spot of the cam, around 2000 up.

I didn't try with the vent plugs out, but I am not sure they would do me much good since I have through hull exhaust. I lost 2 mph also. I don't mind giving up 2 mph, but I want better acceleration if I do.

It wasn't all bad, the prop was very smooth, the midrange hit was awesome, and the boat cornered better than ever. I also pulled 4900-5000 RPM's with 2 people in the boat and 1/2 a tank of gas, so the pitch was right on. I was just hoping the boat would get out of the water better, and that is what I need to justify spending 500+ on a prop. At this point I think I am going to call Brett at BBlades and see what they think would work well as I am not sure an off the shelf prop is going to give me what I want.

Just to clarify some gray area, I am currently running a 21 pitch Stiletto. The boat pulls 54 mph GPS at 5000 RPM on a 1.47 ratio Alpha. This was with 1/3 tank of gas (20 gallons), one person, moderate chop, about 50 degrees ambient temperature with exhaust open. Running the numbers through a prop slip calculator, I am getting 20% slip.

johnfharding

With regard to the plugs, if you have captains call I would think some exhaust is likely to still be routing through the propeller even with the thru-hull turned on. So you might go ahead and open them up all the way and see if it helps get you into the sweet spot.

Smaller diameter 4 blade vensura prop like one of the previous posters mentioned might help the RPMS come up quicker, and keep some of the mid range punch. BBlades labbing the Rev 4's may make it easier to turn them up, but would probably add RPMS up top, and you don't need that.

Thinking outside of the prop.:-)
Just a couple questions on your engine. The cam shaft is as big as you can go which would sacrifice off idle grunt up to the 2000 rpm you were talking about. This combined with the heavy boat are working against you in this application. So outside of going down some on cam size which is probably not an option. Is the carb working o.k.? Just wondered as it might be causing some off idle laziness issues as well. I guess I'm thinking along the lines of maybe its running lean, or the accelerator pumps aren't shooting enought fuel so its bogging a bit. Also is the timing set to factory specs? Also from what I have read on dyno tests for the Vortec heads, the overall timing should be no more than 34 degrees total. Just some ideas.

bbladesprops

A.O. Razor,

Nice job! Call me and we'll send you a BBLADES t-shirt.

Brett