CcanDo

Does anyone know of a manufacture that offers a 40# Steel Fhywheel made from an alloy other than 1018 ? 4340 or similar is preferred.

Thanks !

ezstriper

why would want a 40# flywheel in a boat ??? useless the only reason drag cars use them is when the H/P to weight is lower and it helps keep the rpms up on the launch....on a boat no reason at all...anyway any std trans flywheel with the correct # of teeth will work fine...Rob

CcanDo

We are probably wrong...40# does seem heavy.

However, the plan is to build a new set of engines. While the first one is on the dyno we will compare a 29,35 and 40# flywheel against each other. I fully expect the 40# flywheel to work for our application.

We believe Mercury and other best engine builders use 29# flywheels.

CcanDo

ttt

BenPerfected

Cat,
I wonder if the weight of the flywheel even makes much difference in most marine applications. As the drive line is still fully connected when the prop leaves the water, wouldn't this resistant/drag have a similar effect as a heavy flywheel on the free-rev? I believe that Keith Eickert used mosty 13-15 lbs alum flywheels. If this makes any sense, maybe lighter is better?

CIG3

I agree with BenPerfected. The Eickert aluminum flywheel will give you better acceleration and deceleration, plus less weight on the back of the crank.

ezstriper

I also think the lighter flywheel may work better in a boat, I used to run a super gas car years go with a clutch turbo and played with flywheels, my car was to heavy for the aluminum, but the rev factor was much quicker...just did not leave the starting line good..the heavier the flywheel the more inersha(how ever that is spelled) keeps the rpms from dragging down, on a dyno don't see where you would see much diff, tha only way it would effect a boat is if you were leaving the water and dragging the engine down on re-entry....Rob

Chris Sunkin

Not a big fan of aluminum flywheels- mostly from the durability perspective. The added mass of a steel flywheel will soften some of your occasional throttle mistakes- and if you're not Bob Saccenti, you're making them .

Flywheel has more to do with the matchup to your reciprocating mass than it does on acceleration. If you have a mega-inch motor with a very heavy crank, you probably need a little less flywheel that you do with a 454. In a drag car, you may be attempting to bring a car 4 to 6,000 RPM upwards with each gear. In an offshore boat, once moving you're running at a steady state. Now if you have a KE supercat motor and you're racing, acceleration out of the turns then becomes more of an issue and the tradeoff has a benefit.

On inertia- that's the term for mass at rest- "inert". You're thinking of momentum, or more accurately in the case of a flywheel, the term stored energy is more applicable. But what you're saying is correct- the flywheel stores energy and when you close the throttle, that energy is released, allowing the motor to lose RPM more slowly. Essentially it's a mass-based rpm regulator.

BenPerfected

Chris,
Your flywheel position seems logical...but how does anyone really know the difference in a race or pleasure boat? Can the results be measured? The engine acceleration due solely to the difference in alum vs. steel flywheels is likely so slight (my guess) that Bob Saccenti or anybody else couldn't likely catch the difference. In boat racing, is the acceleration really better out of the turns with a light flywheel? Unless back to back testing was done somewhere like Lake X, you wouldn't know. Even then, it would be difficult to measure. It seems unlikely that a few lbs of flywheel weight pushing a 7000-11,000 lbs. OS boat wouldn't have much impact...kind of like 5-10 HP doesn't.
To me, the best reason to use light alum flywheels, alum engine mounts, etc. is primarily because between them it removes 100+ lbs. of ER weight vs. steel.
Why does Mercury use steel flywheels? Is it because steel is less expensive and most of their customers don't care?
Cat, I give you a lot of credit for your constant pursuit of knowledge and perfection!

Chris Sunkin

If you were to swap back & forth between a 28 and a 40, you'd notice a significant difference in throttle response. The shorter the stroke and the lighter the rciprocating assembly, the more pronounced it would be. But we're talking fine diferences for highly experienced boaters. A guy with a Scarab 30 with Merc 330's isn't going to see a thing. In something like a Supercat- you're talking a pair of very powerful (800+) engines in a light cat and you are talking about what is essentially formula racing. If you can get a fraction of a second quicker acceleration out of each corner, that could mean a place or two higher finish. Again, for a pleasure boater, not a big deal- and for many, nothing even noticeable. In what Merc does- alot of Mercruiser's decisions are driven by the fact that they offer a dependable, comprehensive warranty on their product and justify their premium expense based on delivering reliable quality. Dependability i a pimary issue. If you want performance at the limits of technology, there are many better sources.