Yes! my 300XS is here in europe

[red 5]

Originally Posted by sterling

Sure ,thats right ,but any hotter than 1250 degrees and your burning a piston ,that is on the edge ,and outboard manufacturers never are so close.
They need to be proper tuned for the temperature and elevation where you do your boating.
Also the weight of the boat ,propellor ,speed etc play a rule here.

Thats why it is a general rule (10 % of its rated HP in gallons an hour)
It could be off on some racing engine,s that run extremely lean.

sterling

Yes totally agree ( It's all swings and roundabouts).

[red 5]

Originally Posted by Wacky Racer

The sticker on my saddle and the manual says 6400 max rpm

So who's right Mercury Racing web site or rpm on motor ?!!!!!
I'd like to know. does that mean I can rev my 300x to 7100.
Ill look on sticker. Cheers to all

[Lars T]

Merc test of the 250XS and 300XS


Bass and Walleye boats dynoed the 250XS to 275 and powerboat also tested a couple to 280hp..

[red 5]

Originally Posted by Lars T

Merc test of the 250XS and 300XS


Bass and Walleye boats dynoed the 250XS to 275 and powerboat also tested a couple to 280hp..

So If you have the same cc 3032 and the same gear ratio 1.75 and you can get it to 7000 rpm you have about 380 hp.

[Matt]

Not necessarily. Port timing, injector duty cycle might be limiters.

[Lars T]

Originally Posted by red 5

So If you have the same cc 3032 and the same gear ratio 1.75 and you can get it to 7000 rpm you have about 380 hp.

Have absolutely no idea - just putting down the numbers..

[sterling]

Originally Posted by red 5

So If you have the same cc 3032 and the same gear ratio 1.75 and you can get it to 7000 rpm you have about 380 hp.

If the rpm,s go up more ,and the engine does not drop any further in torque ,you will have more horsepower.
If the torque is falling down rapidly (what mostly is the case),and rpm goes up ,horsepower will drop .
Gear ratio is not involved in here,as measuring on a dyno at the propellorshaft,the ratio in the gearbox has to be in the calcalation for horsepower,so ratio makes no difference ,if calculated properly.

Most dyno,s that have an elecronic load cell,can accelerate while measuring torque ,and engine rpm,that is all it need for calculate horsepower.
Suppose a ratio 1,75:1 ,and 7000 rpm (engine speed),if measured at the propshaft,the dyno will see only 4000 rpm,but in the dynosoftware you have to fill in the ratio(either reduction ,or step up)so actual HP measurement can be done.

sterling

[JamesM]

Todays lesson:

Torque x Revs = Power

Or more accurately:

Torque (Nm) x Angular Velocity (rad/s) = Power(Watts)


For Torque:

Ft Lbs x 1.3557 = Newton meters (Nm)


For Angular Velocity

RPM / 60 x 6.2832 = radians per second (rad/s)


For Power:

Watts / 1000 x 1.3410 = Horsepower


So:

200 Ft lbs x 1.3557 = 271.14 Nm
6000 RPM / 60 x 6.2832 = 628.32 rad/s

271.14 Nm x 628.32 rad/s = 170362.68 Watts

170362.68 Watts / 1000 x 1.3410 = 228 Horsepower

In short 200flb of torque at 6000RPM makes 228 Horsepower

Easy!!!