Friend of a friend is a former Merc engineer and it surprised him. He was suspect of quicksilvers validation and thought a flat plane crank might shake the sensors apart before 100hrs.

Yep. That is a huge flat plane V8. I think Ferrari stays below 4 liters. Ford tried a 5 liter, and it did not go well.

I think some of Yamaha's latest 4-stroke outboards are direct injected.

The flat plane crank what was got us excited.

A Mercury inboard engine is no big deal.

Marcus,

The latest Corvette ZR1 has a twin turbo 5.5L flat plane engine in it.

Thanks. Brad.

Yes. Of course. Forgot about that one.

Ford 5.2 and GM at 5.5 now.

youd want a titanium con rod and light piston to help.

I remember reading an article abt the Yamaha R1 (1000cc motorcycle) flat-plane crank eng a while back. Seems like the only real advantage was the uneven power delivery and how that would give the rear wheel a chance to re-gain traction accelerating out of a corner. Is there any performance advantage in a boat?

All traditional 4 cylinders are flat plane cranks and usually have balance shafts. Motorcycles recently started switching to cross plane cranks like a 90* V8 for more even power to the tire for traction reasons.

You can rev a flat-plane V8 higher, because the exhaust pulses don’t stumble on each other on the way out. It also helps that the crank is lighter, as it is not used as counterweights to the pistons.

(That exhaust issue is what causes the characteristic cross-plane V8 rumble)