AWELSH

I recently had my 496Mag upgraded. The "package" included reworked heads, new cam, new computer, new pushrods, new fuel pump, CMI exhaust and a few other revisions. The dyno sheet I was provided with ranged from 3500 to 5400 RPM. The table below is a short list of several RPM torque and HP numbers.

RPM Torque HP
3500 515 345.9
4000 561 427.7
4500 560 479.5
4800 560 511
5000 556 530
5200 549 542
5400 540 555

My boat is a Checkmate Convincor 270. With the stock 496Mag (375HP) and a 23 pitch Hydromotive Quad 4 prop I could hit 60 mph at 4800 rpm. With the upgraded engine package I can hit 72 mph at about 5400 rpm with the same prop. The engine builder told me to try a 24 pitch Bravo 1 blade (I haven't done that yet). He also said WOT should be anywhere from 5200 to 5400 rpm. I like the 12 mph increase but I don't understand why I wouldn't be able to spin a 26 or 28 pitch bravo blade with the amount of horsepower the dyno sheet indicates. Am I missing something? Aren't these HP/Torque numbers comparable to an HP500? Don't HP500's typically spin 26 or 28 pitch props at a minimum? Please let me know what you think.
AWELSH

Need-the-Speed

Holy Chit! 555 That is better than the Whipple pack. How much did all these goodies cost? Who? How long did it take?

HOUSTONPROP

You really got some bang for your buck.

I have a stock 24 Bravo-one you can try.

also if you go to a 26 it will drop the rpm down to 5,000 OR 5,100 IN THE SAME PROP.

IF YOU DID RUN A 26 PITCH YOU WOULD MORE THAN LIKLEY NEED TO LAB FINISH IT .

The bravo one and hydro are totaly two diffrent props ,Give me a call tue or Monday after noon,Darin 281-580-7767

fountain27ho496

I know hes been working on it. How much?
Are these gps speeds? I'm at a best of 67
gps with a 26 bravo, mag ho. I need a 28
I'm hitting the limiter now. I seem to be the
only 496 spinning a 26, anyone have any ideas
why. Most seem to be 23-24. 12 mph w/o
a blower, good job! John

AWELSH

Darin, thanks for the offer. I was hoping someone could tell me why I can't spin a 28 pitch prop when the motor is putting out 555 hp at 5400 rpm.

AWELSH

fountain27ho496 that is what I mean. You have a 496HO and can spin more prop than I can. Is the boat itself a factor? These are GPS speedo speeds. Tyler did the upgrade.

JIMKID Motorsports

hi guys that upgrade is awsome but what you have to remember about spinning bigger props is the slip rate and that is differnt on all boats that is the prop is slipping not actually pushing all the water you maybe spinning a 26 on a stock 496 but its slipping giving the rpms not the true eficiency my 2 cents wourth

HOUSTONPROP

lamens terms>a 28 pitch prop will pull the motor down into the 4,800 rpm or 4,900 range ,the motor just cant build anymore hp at this rpm there for it stops building torque which produces speed so the 28 pitch prop is holding it back,the higher speed you want you need to build more torque. I am sure some here can explain this in more detail/Darin

Steve 1

Thats real impressive.good luck and safe boating.

AWELSH

I don't post alot, I mostly read threads. That is how I decided on Tyler Crockett for my engine work. You don't need to post alot to gather alot of information from people much more experienced in boating than I am.

I still don't understand why I can't significantly increase the pitch of my prop if I'm currently putting out 555hp at 5400 rpm?? Is my X dimension to low? Basicly I've gained about 170hp but can only turn my stock prop another 600 rpm's. It doesn't make sense to me.

As far as pricing goes I think people should contact Tyler for that. He said he will be putting a big article on the 496 upgrade packages in Hot Boat Magazine very soon.

Thank You
AWELSH