250 PRO XS POWER CURVE

[firekracker50]

Are there places that do dyno tunes for mercurys?
I would be interested but i have never seen one.
I know plenty of great car and diesel tuners, but none for mercurys

[Savage]

Yes.

[EuropeanAM]

Cody- this is just my observation from what others have been through:

By the time you go through all of these modifications, etc... and pay someone to dyno test (and tune) your PARTICULAR engine (this isn't done in a day, BTW...), you will likely be (roughly) approaching what it would cost you to update to a larger engine, that's already properly setup for it's particular configuration.

Not knocking the work some of these folks are doing... just saying that the "four bolt upgrade" is sometimes a better option, in the end.

[firekracker50]

I understand what you are saying Don.
It seems like it was allot easier to "build" horsepower on the old promax motors.
Most days i truly wish i would have never gotten rid of any of my Promax motors.

[EuropeanAM]

They were (and still are) a lot of fun to work with.

The Optis are, however, more environmentally friendly (and fuel efficient).

[firekracker50]

They are more environmentally friendly, but at the cost of our wallets.
I increased from a 900# hull to a 1250# hull when switching from my last 300 ProMax to 225 ProXS. But i did not notice much of a fuel savings. No more than i would have expected to see going from a 300ProMax to a 225ProMax. I realize a 225ProMax is 2.5L instead of 3.0L but I would have expected greater fuel savings

[EuropeanAM]

They are more environmentally friendly, but at the cost of our wallets.
I increased from a 900# hull to a 1250# hull when switching from my last 300 ProMax to 225 ProXS. But i did not notice much of a fuel savings. No more than i would have expected to see going from a 300ProMax to a 225ProMax. I realize a 225ProMax is 2.5L instead of 3.0L but I would have expected greater fuel savings

Don't know that you should have expected much different from your results.

25+% hull weight added
+ 25+% Horsepower Decrease
_______________________
Lower HP Engine, Working Harder.

[firekracker50]

Yep, I completely agree Don.

Here are some numbers I've been tracking over the years.

Untitled.jpg

[Wheelman]

If this chart came from the engine I think it did, it's a 2005 era engine (and required 91+ octane fuel, higher compression, and a different PCM Calibration).

The current production models in the ProXS lineup will produce their PEAK Torque/Horsepower combination in the 5850-6050 RPM range, with an average PSHP output of approximately 263.

The only time HP and torque are ever equal at the same rpm is 5252, torque will always peak at a lower rpm than hp.

I never realized the 10% rule was started in the 80s because Yamaha rated their outboards at the propshaft or so I read on another post by Wayne.

[EuropeanAM]

The only time HP and torque are ever equal at the same rpm is 5252, torque will always peak at a lower rpm than hp.

I never realized the 10% rule was started in the 80s because Yamaha rated their outboards at the propshaft or so I read on another post by Wayne.

Sorry bud- we are not talking about "equal". We are talking about PEAK. I'm sending you a PM now.

[Wheelman]

Sorry bud- we are not talking about "equal". We are talking about PEAK. I'm sending you a PM now.

Torque and hp can't peak at the same rpm though, I'm guessing torque peaked around 4500 rpm given the fact the hp peaked around 6000rpm and other 3.0L graphs I've seen posted. Which would mean torque produced at the crank at 4500 rpm was 320 ftlbs based on the hp numbers posted, that translates to around 300 propshaft ftlbs which sounds about right no?

Edit: it's actually making slightly more torque at 4000rpm based on the hp numbers posted, I calculate it's making 324 ftlbs at the crank at that rpm. It's only making 305ftlbs@5000, 281ftlbs @5500 and 258ftlbs@6000, hope that helps make things clear.