Edward R. Cozzi

Damn! Just use the one MerCruiser sends with the engine and take advantage of the information they already paid to figure out. If you insist on trying another combination, simply install a different flywheel and take it out for a ride and see for yourself if it works or not. If you're looking to have an engine that over-revs faster than any human can feather the throttles when the prop becomes unloaded, then go for it.

BenPerfected

Here is an idea. In a twin application, put an 8-15 lbs alum flywheel in one engine and a 30+ lbs steel flywheel on the other. Run at maybe a steady 5000 RPM and jump a wake, chop the throttles back as the props break loose and measure the RPM peak/curve (how?) on both. My bet is you won't bother to pull and re-rig either engine based on the difference.

Edward R. Cozzi

I'm going to fill you guys in on some flywheel history...

The flywheel was originally invented by Isidor and Marybelle Trundle, (yes, they also invented the hideaway bed), in the early 1700s. Their first design was hollow and they kept filling it up with a mixture of corn flakes and farina to experiment with different weights and consistencies. Mrs. Trundle was a lousy cook and Isidor was always looking for places to hide food rather than consume it. Isidor stumbled on a near perfect combination with some left-over meat loaf from earlier in the week. The engine revved-up smoothly and when the propeller left the water in Lake A, (where they tested their inventions), the engine reacted favorably. The rest, as they say, is history.

BenPerfected

Ed,
I had heard that Isidor ending up spending most of his time hideing the sausage and he ended up losing focus on most of his other activitivies.

Chris Sunkin

A heavier flywheel will greatly extend crank life.

P.S. Don't fuc& with Cozzi. Just listen & say thanks.

turbo2256b

iTrader: (1)

For drag racing flywheel weight woud depend on how much energy would need to bee stored for the best launch. Mostly depending on the size of the engine vs the weight of the vehicle. There are also increased mass flywheels. Due to the way they are machinedd a 30 lbs flywheel could have the inertia of a 40 lbs one.

Not shure why a boat would need the stored energy other than re-enteing the water to reduce shock load and help maintain rpm on impact. As Chris stated a heaveier flywheel increases engine life it smooths out the pules between the cylinders firing.

Edward R. Cozzi

Actually there is some truth to that.

Mrs. Trundle was suspected of fooling around with a Great-great Grandfather of Carl Kiekhaefer...

Chris Sunkin

About 15 years ago, I was helping a friend with an engine project. He was a fairly well-known pro-stock engine builder. He had a theory about some things that were going on inside an engine- basically that on launch, the tires went through extremely brief periods of slip and stick which, if isolated and slowed way down, amounted to the engine loading and unloading at a fairly high frequency. His theory was that induction systems could be tuned around this frequency for a more stable inlet charge flow. In his experiments, he discovered that flywheel weight could make it go away, or at least lessen it to the point it wasn't a factor. Problem was, it took over 70 lbs to get it there. He did discover significantly less rotating assembly fatigue with the larger flywheels. Everything from rods and rod bolts to cranks to main bearing caps benefit from flywheel mass. The downside is a drag engine with a 70 lb flywheel is a real stone. I don't know how he ever made out on his intake tuning experiment- he got sick & left the biz shortly thereafter.

mrhorsepower1

There is really no ideal weight of a flywheel. Here again flywheel weight is directly related to many variables. Horsepower,weight of the boat/ vehicle,inertia, ect.... play a roll in selecting the proper weight flywheel. We have run many light weight aluminum flywheels in race boat applications were the boats are fairly light, higher HP , and we are looking to accelerate the engine. In a heavier boat such as an Apache and non-step hull design with Supercharged engines I like around a 25-28 lb. wheel. The weight of the flywheel will in rougher water help keep the mass of the boat accelerating. In this type of application we have gone from a 40 lb. wheel to this weight above and picked up 100-200 rpm do to the reduction of rotating mass. Yes, in Drag race applications weight and horsepower also relate to flywheel weight.

Edward R. Cozzi

FINALLY, Dean! Where the heck were you when I needed you?

Hope you're having a Great Thanksgiving!

Ed