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2011 244ZT prop selection

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Well I tried a 23 pitch rev 4 and it wasn't really what I wanted. It ran 68 mph at 4800-4900 rpm. My labbed bravo ran 70-72 at 4800. I bought it already labbed. And my stock bravo ran 68-69 at 4500-4600 rpm. I think I'll get the stock bravo labbed to my exact boat, since I smacked bottom with my other labbed bravo.
 
I'm bringing this thread back for some prop talk. So I was doing some numbers and the slip percentage for that 23 pitch rev 4 was 4% slip which is crazy low. So in theory would a 25 pitch rev 4 bite as hard and have close to the same slip numbers. I know ill lose 200 rpm going to a bigger pitch.
 
25p Rev 4 is a big prop. If you were at 4800-4900 with the 23p, your rpm's will be too low. 2" of pitch is closer to 500 rpm drop.

Once a prop is labbed for your hull, nothing out of the box will compare to it. If you like the speed your labbed bravo gave, that is probably your best bet.

Powertech makes some interesting props I would like to try eventually. They are supposed to do better than merc props out of the box.

The OFX4 should be similar to bravo I only with more rake and cup. I think that would be good for you to try.
http://www.ptprop.com/index.php?pag...facturer_id=0&option=com_virtuemart&Itemid=46

The OFS4 is more like a Rev 4 with larger blades.
http://www.ptprop.com/index.php?pag...facturer_id=0&option=com_virtuemart&Itemid=46

Is your engine out of warranty yet? From what I have been hearing, the only difference between the Mag and HO versions on those is computer only. Camshaft part numbers are the same unlike the older 496 Mag/HO. I believe Dustin Whipple has the upgraded PCM programs figured out for these new ones and I believe his stage II tune for them nets around 450 hp on these newer gen motors. Search on OSO for it, there was discussion on it a while back. That would be a huge bang for buck and you would spin that 25p rev 4 afterwards.
 
Thanks for the reply. I will look into calling whipple today. I didn't think I would lose that much rpm. You have to admitt that those numbers on the 23 pitch rev 4 were pretty good when it comes to slip.
 
It is good Merc went back to the older platform and modernized it. They are very stout factory engines. Can't go wrong with mods from Whipple either.

Does your engine run the catalytic converters? If so you might want to look at ditching those once your warranty is up. If the non-CAT manifolds are similar to the 496 manifolds, they flow good from the factory and even better once the turbulators have been removed from between manifold and riser. There is no advantage to changing to aftermarket if you have those. Even the new Merc Racing 520 uses them instead of headers like the 525.
 
I have the cats. I was doing some research on ditching them and from what i read it was a big pain in the butt and that the boat got the best fuel economy with the cats and o2 sensors working properly. i just called whipple and am waiting on a call back from dustin. Im sure he will clear it up if the cats are good or bad. 50 more horse with the stage 1 upgrade and 85hp with the stage 2. i was thinking about doing the stage 1 to save the life of my motor rather then the stage 2 :banana:
 
you would still need O2 sensors in the exhaust if you removed cats. usually easily done with small block between riser and manifold that is tapped to accept them. Dustin wont steer you wrong, would know exactly what to do and what is best. IMO the only way stage II would hurt the longevity is if you used poor quality gas because it requires 91 octane. Stage I requires only 89 octane. It is still the same rotating components and it sounds both kits raise the rev limiter. I personally wouldn't worry about effecting longevity. Even with stage II, you are still under 1 hp per cubic inch displacement output. Your new chevy truck has a much higher hp/inch ratio and is still very reliable in the long run. Crazy cam profiles, sustained max rpm, reversion, and poor driving habits are what kills marine engines IMO. I doubt Whipple tunes them to the absolute ragged edge to make these numbers otherwise he would have issues when they failed.
 
Well I just got off the phone with Dustin at whipple. The stage two kit adds 85hp if I remove the cats. He said that he wil tune the PCM so that it knows I won't be running cats. I'm pretty crazy excited. 85hp is unreal. The mag and and the HO have the exact same internals, the difference is that the mag has a throttle limiter that needs removed on the cable and also the PCM is way detuned. It will raise the rev limiter to 5400rpm and I will need to run 93 octane. My question is how much RPM will 85 hp give me? I'm just curious about how fast I will be going.
 
That is awesome! Gotta love the new motors!

The 85 hp will at least cause you to jump up 2" in pitch....at least. Without changing pitch, you will probably bounce your current prop off of the rev limiter at 5400. You will need to re-prop to take full advantage of the added power. Looking at the dyno graphs Dustin gives for the 8.2 MAG Stage II kit:
whip82_2.jpg

The kit gives a very nice and flat HP curve from 4800 all the way to 5300 before it starts to drop off. The torque curve is also very stout and flat. I would say that your target RPM to prop for would be 5000-5200 rpm. That gives you a little leeway if you are light on fuel, gear, or get some perfect chop and the boat is feeling fast, you won't bounce off of the rev limiter when you gain a couple extra mph from cool air temp or perfect water conditions.
 
The throttle restriction isn't on the cable. It's actually an air flow restriction between the spark arrestor and intake. Here is a pic comparing the pieces from the mag and the HO. 9FA509EC-96D8-4F89-8D89-06851935F8C4_zpsw4vulecg.jpg
 
Just dont go boating in California with a modified emissions-controlled engine! Big fines/possible boat impoundment if found. Hopefully your area is not controlled by a bunch of smog nazi's that will give you trouble if they found you have modified an emissions-controlled engine.
 
Last edited:
fox88gt said:
Just dont go boating in California with a modified emissions-controlled engine! Big fines/possible boat impoundment if found. Hopefully your area is not controlled by a bunch of smog nazi's that will give you trouble if they found you have modified an emissions-controlled engine.
Click to expand...

It's pretty laid back where I boat. The boat commission are only looking to keep everyone safe and give your occasional BUI to those who are acting stupid.
 
fox88gt said:
Just dont go boating in California with a modified emissions-controlled engine! Big fines/possible boat impoundment if found. Hopefully your area is not controlled by a bunch of smog nazi's that will give you trouble if they found you have modified an emissions-controlled engine.
Click to expand...
More reasons I have no desire to visit Cali.....
 
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