Promax vs 260 vs prostock

[90 5.0]

I've seen various dyno charts for stock promax. They usually fall between 240-249 hp on the limiter.

Does anyone have a dyno chart for a pm with raised limiter compairing 260@ 8k vs a pm @ 8k etc

what about a stock 260 dyno and one with 26cc heads.

Pm with drag electronics with 26cc heads

prostock legal powerhead with 32 or 26cc??

thanks!!!

[texasvector]

Subscribed.

[tux974]

^^x2^^

[16ft superboat]

^^x3^^

[Dave Strong]

X4

Dave

[Go Time]

336404

This sheet is from a stock Promax with SVS and Brucato ECU with dyno tune.

[tux974]

336404

This sheet is from a stock Promax with SVS and Brucato ECU with dyno tune.

Now get Lee to play with a 260 and post up needed details.....;):D
Stock 38CC heads correct?

[Go Time]

Yep, stock heads and 23 degrees WOT

[texasvector]

I see the torque falling off...but when does the HP fall off higher than 7500?

I would guess the prostock motor's torque would peak lower. But when u turning a 22" who cares;).

I'd love to get my hands on a prostock tune for a brucato....gonna have to sneak one off some bodies boat at the race this year. Ninja skills!

[Go Time]

I have my limiter set at 7600 rpm

[Dave Strong]

I have a Merc Racing brochure somewhere that had HP and torque graphs. All the 2.5's showed peak torque arounf 5-5300rpm, 280, Pro Max, and Drag.

Dave

[whipper]

So what is the difference in a promax prostock compared to stock? Fuel delivery? Numbers look great!! Mine revs with Tonys box to 7500+ with 33cc heads. But at around 7300 seems to be the sweet spot as confirmed buy the chart it would seem.

[texasvector]

I know the prostock 200 motors are running high psi curves with custom tunes....some run 56lbs some turn down to 50 lbs

I would think pmax would benefit the same doing this

I know my laser front 260 woke up when I went to a 56lb curve

[90 5.0]

I know the prostock 200 motors are running high psi curves with custom tunes....some run 56lbs some turn down to 50 lbs I would think pmax would benefit the same doing this I know my laser front 260 woke up when I went to a 56lb curve ive seen a "prostocked" pm run once, it was pretty mean for a unported pm. defintitley made a big change. interesting that you put a laser injection on a 260, most i see are horns on pm's LOL. But for 660, i'm wondering if a promax with drag electronics would be faster than a 260. No doubt in 1320 the 260 would get it, btu in 660 i'm not sure...

[texasvector]

Well..it was a 245...took carbs off and put efi

[Dave Strong]

336491

Well here they are, my mistake didn't show a 225 PM but all the motors peak torque at 5000rpm.

Dave :)

[dwilfong]

remember torque peeks at VE and that is controlled by the eng stroke. so all eng with the same stroke will all peek the same place. Then RPMS take over and produce the HP. how much torque you produce will determine how much it drops after the peek as the RPMS rise.
If you are running a light boat the max torque is not as critical and the RPMs become the work.
The trick is to make good torque at the peek and still be able to rev the eng. Most timing # that are geared to high RPM do not build max torque.
Check the max torque # and RPM of max hp# on different eng and you will see the correlation.
Look at the % of torque drop after the peek. thy are the same I bet. so if you have more to start it will carry more higher in the RPM range. This is what builds HP......Torque..........................

[Dave Strong]

Porting and exhaust chest cut will raise the HP and what rpm it makes peak Hp.

Dave

[Go Time]

Am I the only one willing to share??? There have got to be a few others with dyno sheets on their motors.... lots of views but short on the data :cool:

The curve that Clay developed had changes in the mid range that may have push the torque peak a little higher (closer to 5500). We did a bunch of runs to just 6000 to concentrate on the mid range part of the curve.
Mark

[16ft superboat]

336404

This sheet is from a stock Promax with SVS and Brucato ECU with dyno tune.

Was this at the prop or crank?

[Go Time]

Land & Sea Propshaft Dyno.

[90 5.0]

Bumping,

Still no one with a prostock dyno they want to share?

I found an old land and sea chart with their mods vs hp on a sales brocure.

they claimed 305@9100 with a 2.4 200 "competition" prep but their was no description on how they did it, ie what compression porting or not etc?

Are prostock motors making over 300 @ 9500???

[mrcrsr]

i dynoed a 260 i had built awhile ago, had 31 cc heads,on pump gas with aces, port angles changed slitely, exhaust chest opened, and some other mods, on monty's dyno it made 326 prop hp, and was already making 300 by 6k rpm

[90 5.0]

i dynoed a 260 i had built awhile ago, had 31 cc heads,on pump gas with aces, port angles changed slitely, exhaust chest opened, and some other mods, on monty's dyno it made 326 prop hp, and was already making 300 by 6k rpm

Those are great numbers!

I'm trying to compare motors with stock porting only though..

[Go Time]

Was the 260 using a horn or SVS intake? That's pretty stout...a friend has a 260 that dynode at 299 (pump gas) and thought that was pretty strong (which it is)...but 326 is way strong,

[mrcrsr]

Horn that I back cut inside, I did a bunch of other little things in that motor as well

[Dave Strong]

Horn that I back cut inside, I did a bunch of other little things in that motor as well

Little things add up. ;)


Dave:)

[mrcrsr]

Incidentally, back when I had my virage, I was building 2 260's for a 24 skater, and the customer had Brucato pcu's and svs. He paid me to pull my powerhead and put one of his on. I ran his engine with the pcu and svs, and then put my modified reed plate, spacer, horn and 849849a5 computer on it. My horn setup was faster by 1.5 mph, and speeds over 110,but I had no way to guage acceleration. Incidentally I did tune his pcu setup doing piston readings and used the software to dial it in