TEXASRPM

I will look more into it but for now.

http://www.sterndrives.com/496maghoengine.html

http://www.perfprotech.com/store/art...fications.aspx

HaxbySpeed

Yes

Knot 4 Me

Bob Llyod of Full Throttle Marine has dyno'd a 496 MAG HO at 387.8 HP at the prop at 5,000 RPM. You can find dyno sheets at his site: www.fullthrottlemarine.com

jeffswav

Wrong, the 496 HO is propshaft HP. At least thats what merc publishes......

TW720HVY

iTrader: (1)

Thanks for the input and I understand what you are saying. But wouldn't the extension box and 2" shorty also add to the equation of the top speed as well?

http://www.go-fast.com/boat_speed_predictions.htm

osur866

IMO and experience with running a -2" on a straight bottem V, your -2" isn't really going to help until you get into speeds around 70 an above, like mentioned above it could actually be hurting you if your loosing the ability to carry the bow, the added wetted surface could be a henderence, my .02

TEXASRPM

That is an interesting article.

However, 425 - 388 = 37 HP difference.

504 PSHP - 388PSHP = 116HP DIFFERENCE

Based on the revised 116 HP increase from stock.
8 MPH INCREASE ASSUMING 15 HP PER MPH

7 MPH INCREASE ASSUMING 17 HP PER MPH

6 MPH INCREASE ASSUMING 20 HP PER MPH

Knowing that hull design, beam width, and weight has great effect on top speed and in determining HP PER MPH?

IMO whether 79 or 116 extra PSHP , 66 to 68 would be a realistic top speed number for the 26 Outlaw with that addtional HP

Also, were the speeds recorded by GPS, Radar or DreamOmeter?

I think a Outlaw 26 would have trouble breaking 70 with 504 HP?

I see that BobL runs a Land and Sea Dynometer prop dyno. What type of dyno does Mercury run to verify there prop shaft hp ratings?

Thanks

TW720HVY

iTrader: (1)

The speeds I am posting are GPS.

I understand that the Nordic is a stepped hull and ours is not. It is also a 28 foot boat but we probably have the same amount of hull in the water. Their average was 63 (just on the concept of the step this number should blow ours away but it doesn't) just about 1.5- 2 MPH faster than ours with a 496HO. But with the Raylar kit (525) it picked up 9MPH and was comparable to the blue 525. And with my 575 kit/upgrade (560HP) I picked up 5MPH so far and I should be content with that because it is an Outlaw. I understand I have to adjust the A/F ratio and fuel pressure I get that. 525 (473) getting 72MPH is realistic and ours getting above 70MPH is not. This is where I am a little confused.

Then I was under the impression the E-box and shorty would also improve speeds and now some are saying they will not.

Something is wrong.

Who and what do I believe at this point?

jeffswav

Rick, I am not trying to stir you up here. But remember when we talked several month ago and I recomended doing one thing at a time, that way you know were your speed came from. Everything I have done I have seen results, raising my x dim up 3" gave me about 3-4MPH, and thats with no xbox. I do think you could go up higher, I would have used the 3" raised box since you needed new exhaust anyway. I did my engine work first then later raised the x, some guys have done the xbox first then the engine later. With what you have done you have no idea what helped you. I do think you are on the right track with getting the O2 checked, just need to get the O2 bungs welded in, not sure why they chose to put EGT bungs in, O2 is way better for tuning. You have to have a perfect tune to get the best speed. Knowing what to shoot for is the hard part. I lost a litte speed this year, I started leaning it out in very small amounts and now I am almost back to normal. I was using 12.5 for my WOT target, I have it at 12.8 now and seems to be doing well for speed. I am thinking about leaning out to 12.9 and seing what that does. I just don't want to go BOOM !!!

Raylar

Just to give everyone here some more credible info:

Raylar has dyno tested on ours and other dynos probably more 496Mag and 496HO engines both stock and with our various upgrades, kits and engine packages than almost anybody on the planet.
A stock full y equipped 496Mag makes about 365-380HP at 4800 rpms at the crankshaft.
A stock fully equipped 496MAG HO makes 421-430 HP at 5000 rpms at the crankshaft.
This is on calibrated, SAE standard testing, with correction factors and specific fuel gravity calculation adjustments and these numbers are pretty much spot on - PERIOD!

Best Regards,
Ray @ Raylar