Planetwarmer

Im curious as to why people choose a Merc 2.5 over another merc? What is the difference between these engines VS the other merc outboards? Some of the other outboards have a higher rated HP, why do racers prefer the 2.5s over the higher HP motors? I know the 2.5 is a lighter motor, why is this?

Thanks

merctwofive

The 2.5 is just a way nastier engine than any other. Period. The first time you nail the throttle there will be no comparison to the others. Instant brutal power, light weight, higher operating range for prop selection are the big differences IMO. I had twins on my last boat and would do it again, too bad the Gov't. killed these type of engines for the every day guys.

monstaaa

2 stroke, high rpm. in some modified versions as high as 12k rpm. the power to weight ratio is unparelleled. th acceleration as stated above is just brutal. i have rigged maybe 100 or more of these engines on single , twin and triple applications and never let down.

Too Stroked

The light flywheel on these motors also gives them extra snap. I agree - the accelleration is out of this world. Then there's the sound ...

RBT

375 lbs in offshore trim
can safely turn 8-8500 rpm for extended periods
The best engine builders (Power Performance) can exceed 400hp (requires race gas)and still have some reliability....... but get out your check book
A drag motor will turn 10 500-10 600, at 10800 the crank lets go. There is a horrible harmonic, sorry but 12k is unrealistic. Maybe on a tach, but reading the ECU for rpm tells otherwise. Add that the ECU is not capable, it breaks down at 11500. (the rev limiter has nothing to do with it, I program mine with a 13k limiter)
With a billet crank and h beam rods low 11k was being seen in UIM F1, but they now have a 9600 rpm limiter to help keep the motors from going palestinian.
Lightweight flywheels DO NOT help acceleration, only reduce the stress on the upper bearing, the gyroscopic effect at rpm is brutal.
If you think a 2.5 is mean, take a 300X, put a 300XS stroker crank in it, some cunningham rods and S3000 port timing and you have a real motor!

Planetwarmer

I took out a skater 28 with twin 2.5s and am in love. I was just curious as to why that seems to me the motor of choice over all others including the 300X (etc).

Are guys using the 300X in offshore races, or still the 2.5 for some reason?

JRider

iTrader: (1)

In stock form the 2.5 260 and 280 had warranties which made them attractive. As mentioned before, they are light. The 2.5 are easy to work on and there are a lot of parts out there for them.

Maritime_Eng

Anymore info on this combination? Who built it? What kind of HP did they produce? Besides porting and new crank and rods what else was done to this engine?

Thanks!

Too Stroked

[QUOTE=RBT;3197798]
Lightweight flywheels DO NOT help acceleration, only reduce the stress on the upper bearing, the gyroscopic effect at rpm is brutal. QUOTE]

Interesting. Doesn't the additional rotational mass (of a heavier flywheel) impeed a engine's ability to spin up quickly? "Snappy" is the best word I can apply to what a 2.5 EFI kick in the pants feels like. Yes, some of that is just raw horsepower, but some of that is the engine's ability to spin up quicker - isn't it?

4mulafastech

The 2.5's are great engines and nitrous oxide is also an option. I had twin 1993 2.5 carbed engines (245HP) on my Talon 22 and installed Nitrox systems by Hydro Dynamics (110HP each!). 710HP on a 1200 lb hull. Acceleration was unbelievable. Put over 280 hours on the engines. Only failure was a broken prop shaft (when on the bottle) which took out the upper crank bearing. Man, that was a fun rig!