I/O Enchanter Prop and RPM's

[SneakyPete]

Hey all,
I just picked up a 25p Mirage, and I am starting to modify the 350. My desktop Dyno says I should be near 440hp (6k rpms), and 440tq (4500rpms). I imagine the HP numbers area little inflated, but I imagine the tq and rpms are close. What rpms's should I be shooting for top speed? Is 4500rpm's the magic number? I don't want to be runnning this thing at much more than 5000-5500rpm. Should I keep going up in pitch until I can't get too far past 4500rpm?

 

[xsive]

What have you got for a drive on that unit? The alpha 1's and it's predecesors didn't handle anything more than 350hp real well.

Your RPM's are going to be dependant on what you modify your motor to. A dyno sheet is a big help, but if you aren't dynoing I guess it's cam specs and seat of your pants. (Trying props)

 

[bowtie]

They say for max mph you want to turn the motor to where it makes peak HP. So if in reality your motor made it's peak hp at 6000, that is what you would want to turn for max mph. That said, unless you actually dyno the motor you will not know exactly where your peak is going to fall and I would tend to be a little conservative on the guesstimate. Plus the fewer rpms you turn the motor, the longer it should last. You are familiar with my set-up, the camshaft supposedly makes power from 2000-6200 rpms (according to the cam card), and when it was dyno'd the first time they actually spun it to 6000 rpms and it continued to make more power, however after the new ECU was hooked up and they dyno'd it again they only took it up to 5500 rpms. It made more power at 5500 with the new ECU than it did at 6000 rpms with the old one, but it was still climbing when they stopped the pull. With that said, I turn my motor 5400 at WOT with all but one of my props (have turned 5600 rpms with too much trim, but no more mph)and that props turns 5200 rpms. I am planning to install a fresh set of springs before next season and then I may try some props that will allow the motor to turn a few more RPMS. The set that are on the motor now are over 10 years old, and if they were trully set up to what it states on the build sheet, they were set up incorrectly and most likely do not have adequate spring pressure to control the valves at much higher rpm levels (according to the build sheet they were set up at 1.750, but they should have been set up at 1.688). Anyway, the props I have rune are the following:
Turbo 3 blade 24" pitch Turns 5400 @ 71.8 mph
Hydro 3 blade 23" pitch (I think) 5400 @ 70.8 mph (about 300 extra lbs than with the other props)
Hydro QIV 22" pitch (labbed) 5400 @69.8 mph
REV 4 22" pitch (stock) 5200 @ 66.4 mph

My boat has the Alpha SS which is supposedly about 2" shorter than a standard Alpha, with the prop centerline about 5" below the pad with a 1.5/1 ratio.
I would go ahead and try the 25" Mirage, but my guess is it will be too tall and you will want to go down on the pitch to get the rpms back up.

 

[SneakyPete]

bowtie,
Look into those comp cams beehive springs. The magazine I have, Power and Performance, raved about them, they tried them in Vortec heads and also on a BBC. With the BBC, they were having valve float issues at 5600, with the Beehive springs installed, they were able to spin in to 6500rpm. Also, Horsepower TV on Spike raved about them. They are much smaller at the top, allowing the use a much smaller retainer, which is much lighter. Also, you can you use TI retainers for even more weight savings. The beehives go for $160-180, the steel retainers are $60, and the TI retainers are $280. I am putting the beehives and steel retainers on the Vorted heads I just ordered. If you can't find that magazine, let me know and I will photocopy the articles and send them to you.

 

[bowtie]

I am very familiar with them... They were originally designed for the new LS series GM motors of which I have one in a 2000 WS6 Trans Am. I have read claims about them in one or more of the hot rod mags and know of several people that run them. I do not doubt that they are good spring, but they are still relatively new. They are also not recommended for anything over .600 lift even though they should be able to handle .650. I know they work relatively well on the LS series motors, but the serious builders with serious intentions still opt for the dual springs over the behives. Also, the valvetrain on the LS series motors are lighter than the old small block stuff and much lighter than the big block stuff. I am by no means knocking them, I would just prefer to go with something more traditional until I have seen more sucess with those. Besides a good set of dual springs will cost considerably less and you will still have to buy a set of retainers with either option. One other thing to consider with a dual spring is that if one of them breaks, even though the motor may run like crap, the other spring may prevent the valve from being eaten by the motor, which is always bad news. Also, I already have a set of some 1.460 crane duals which would will swap right in place of my 1.465 springs which are in the boat now.

 

[88 Enchanter]

What kind of prop were you running with the stock 350 260HP Mercrusier, I am running a Quicksilver 19p on my stock I/O (aftermarket intake and carb) and am turning close to 5,400 RPMS at about 64mph. I have a 23p clever that I have yet to try, but am curious to see what everyone else is turning and what kind of speeds they are getting (Checkmatefever,Sneakypete,CVX16CVX) Fill me in on your setups, I'm curious!

 

[daren34]

props

hey 88


sounds a little high

try a mirage and see if that will bring down the r's a bit
the guicksilver is 13.5" dia and the mirage is 15" dia

a 19 mirage will probably bring it down about 200 or 300
ansd you might see a higher top speed

it should also soften the wakes a bit

daren

 

[CheckmateFever]

What kind of prop were you running with the stock 350 260HP Mercrusier, I am running a Quicksilver 19p on my stock I/O (aftermarket intake and carb) and am turning close to 5,400 RPMS at about 64mph. I have a 23p clever that I have yet to try, but am curious to see what everyone else is turning and what kind of speeds they are getting (Checkmatefever,Sneakypete,CVX16CVX) Fill me in on your setups, I'm curious!

I'm running a 23p SS prop on mine, according to the tach about 4200 rpms, i might be able to trim it farther but i don't want to hurt the drive, i bring up it to about 3900 then trim it out till i hit 4200 and i don't dare go any more trim, no limit switch and i think i'm probably over triming as it is. I don't have a GPS or a working speedo for that matter so i dunno what the speed is, low 60's i was guessing, thats what my buddies boat ran and i could keep up side by side with him. Keep in mind i don't have thru-hull exuast so thats going to kill my RPM's over everyone else. This prop thing has me very curious too, i read the big prop artical in Hot Boat this much, but i'm still not sure what to get for boat. I've seen countless pics of Enchanters with cleavers on them, and they claim "70 mph" which may be possible, i dunno, but i've heard that cleavers suffer everywhere else but top end, bad for cruising.

 

[88 Enchanter]

Had the boat out again with myself and two of my buddies and ran it like I normally do, but I guess at 65ish mph I wasn't getting as accurate of reading as I thought I was. I had one of my buddies watch the tach as I ran it up to speed and he said it was right around 5,150 so a lot better than 5,400. My question is then, what prop would be best to get some more MPH out of it, but not lose too much bottom end. Am I ok running those kind of numbers with my setup or do I need to have any concerns. I do have a 23p clever that I want to try, does anyone have any guesses what it will do for me in comparison to my 19p I am running now?

 

[SneakyPete]

There is a 21p Mirage I have found. Do you think this would be a good size to buy? I am turning 4200rpm @65 gps right now. It has spun 4800 rpm with a 23p cleaver (@60mph). Some one recomended trying a Tempest, tho, any ideas?
I have also found a 23p Tempest Plus and 21p Mirage Plus. Any idea on how the Tempets plus or Mirage plus would perform. Whats the difference between the Mirage, Mirage Plus, and Tempest Plus?