2.5L - EFI - 375hp

cegerer · cegerer's Garage

OK, it's not a Porsche flat 6. The F1 boats are in town this weekend and these things are running 2.5L Mercury V6 motors with fuel injection (normally aspirated) on gasoline, and crank out 375 horsepower!! Incredible. That's nearly double the output of my 2.5 motor! -- Curt

TimT · 06-21-2003, 06:16 PM

Very cool,

I notice 2 injectors per cylinder!! are they running proprietary EFI or Motec or EFI units?

Neilk · 06-21-2003, 06:22 PM

Are they 2 or 4 stroke engines? How durable are they and how bad are their emissions?

My parents have a 30ft Grady White with two Johnson 225s. It's disgusting how much those engines pollute the air. At every cold start, they put out more smoke than a Motor Meistered flat-6.

jluetjen · jluetjen's Garage

I'm pretty sure judging by the picture that those are 2-cycle motor. Note the carb at the front (bottom) of the motor and the lack of any cams or valve covers at the top.

2-cycles will generally give almost twice the HP of a 4-cycle motor of the same capacity and engine speed. Why? Basically because they have 2-power strokes for every 1 in a 4-cycle motor, and they don't have a compression stroke. But all is not perfect - as mentioned they are VERY dirty and have a very tight torque curve compared to a 4-cycle. When 2-cycles are are "on the pipes" (ie at that point in the rev curve when the intake and exhaust pipes are all in harmony), they are REALLY good. But when they are "off the pipes" they are much worse then an "off-cam" 4-cycle motor.

The peakyness of a 2-cycle engine isn't such a big deal in a boat as compared to a car. Lots of the DSR or CSR racers in the SCCA use 2-cycle motors, but they often resort to a CVT belt system or centrifical clutch set-up to keep the engine close to the peak output rev range. But the majority of the winners are using 4-cycle motors of either piston or rotory design due to I suspect the increased flexibility.

The truely astounding thing about those F1 boats is their cornering. I guess when they dig in their sponsons when cornering they are really violent. We're not talking about wimpy 1-3 G turns, but I guess more like 5G turns.