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View Full Version : Promax 300 & 300X overrated HP???



Toffen
04-24-2001, 04:42 PM
Hi!

I read the test of Promax 300 and Promax 300X in Bass & Walleye Boats and John Tigers comments regarding overrating; i.e Promax 300 pulling 280HP and Promax 300X pulling 290HP based on fuel consumption.

I had a Evinrude 225 Fich the summer of 1999 bolted to my Phantom 25. The top speed was 65 mph spinning a Raker 22 at 6.100 rpm with 1.86 reduction. In the autumn I replaced the Evinrude with a Promax 300 due to fauling. The top speed was done with new spark plugs. The new speed with the Promax 300 and a stock Raker 24 was 72 mph. The boat set up was just as before i.e setback, weight, conditions, etc.

I have read that normally you have to add 12-15 HP to gain 1 mph. To get 7 mph this should imply 84HP - 105HP. So if the Evinrude pulled 225 HP, the new Promax 300 should be underrated pulling 309HP - 330HP .....

Now my Phantom runs 76 mph at wot with a Chopper II 26 inch at 6.000 rpm. Since 1999 I have rebalanced the boat, blue printed the bottom, tweaked the props, etc. So more speed is possible without more HP!

Any thoughts about overrated Promax 300's???

Cheers, Toffen G - Norway

WillyT
04-24-2001, 05:09 PM
In the latest edition of that mag., a guy from Mercury sent in a letter that says that Tiger's use of fuel consumption to measure horsepower does not work on some of the newer, more sophisticated engines. Tiger answered back that it still works on EVERY engine he has ever tried (so who knows?) I found the Merc letter interesting since I had also sent the mag. a letter suggesting that they buy a dyno to test horepower in a more direct way (I think John Tiger is the best out there, but I also have my doubts about fuel consumption being an accurate method to measure horsepower on today's newest engines). In a separate letter, John Tiger told me that a 300X will push the 22' Cougar tunnel over 100 mph given a long enough lake and a driver that knows how to drive that boat (other mag. tests of that boat/motor combination did not get speeds nearly that high). If it will push that relatively large and heavy boat that fast, then it can't be "overrated" by much, if at all. From tests I have read, I truly suspect that the 300 had trouble really putting out that much at the prop. I think the 300X, however, puts out a little more than 300 (based only on different reports I have read).

jimmyb
04-24-2001, 07:31 PM
I can tell you that the current production 300x motors burn about 30-31 gallons per hour at WOT. The one that Tiger tested burned about 27 gal/hour. Unfortunately for the test in B&WB magazine, mercury sent one of the pre-production motors that ended up having a stumble during acceleration and (in hindsight) didnt put out the horsepower it should have.

as far as the Mr. Tiger's way of estimating horsepower, I my opinion, it is basically a rule of thumb. I personally think it accurate to about +/-10%, Mr. Tiger thinks it is more accurate.

I can tell you for a fact that the 300X is a potent motor, and if you look at the design of the front between the old 300 and the 300x, you will definately see improvement in the efficiency. I drove a 300X on a stroker bass boat, and it was one mean ride (which is saying a lot, coming from an Allison owner!)

Toffen
04-25-2001, 02:50 AM
Hi

Thanks for replies.

I got a mail from Matt Riddle at PerformancePlusMarine, and he told me that a Promax 300 pulled approx. 280HP. Initially the Promax 300 should have been labeled Promax 280, but since Merc at that time upgraded the 2.5 litre 260 HP til a Promax 280, they labeled the new 3.0 litre to Promax 300....!

However, according to Matt Riddle his phase 4 package (modified ECU/ECM, hotter heads, new exhaust tuner, new reed cake, etc) will burn both the old Promax 300 and the new Promax 300X. The phase 4 package will add 40HP on dyno. Have you any experiences with PerformancePlusMarine?

I presume the new Promax 300X is pulling 300-310HP, when the old is pulling approx. 280HP...

Cheers, Toffen G

Ray Neudecker
04-25-2001, 06:56 AM
i have known and done buisness with Matt and Performance Plus Marine longer than I want to admit.He is a very straight and knowledgable person. He stays on the leading edge of Mercury High Performance and has for many years.You will not go wrong in dealing with him. I wish I could say that about mire people in this industry.

jimmyb
04-25-2001, 07:09 AM
i am curious about the exhaust tuner... does he make a new one? or does he modify the existing one?

as far as his horsepower improvements, I would have to reserver opinions until i saw it on a propshaft dyno.

I can tell you that the 300x motor is definately on the + side of the 10%

Toffen
04-25-2001, 07:26 AM
Hi!

It is a new exhaust tuner. The hotter heads are milled stock Merc units. The reed and reedcake I am not shure about. The ECU/ECM is modified by Rapair/CDI. The SVS Brucato is added as well. According to PerformancePlusMarine they have dynoed a modified Promax 300 to 314HP... Any ideas and experiences??

Cheers,

Toffen G