Lightning the flywheel worth it?

[damianfishy]

Hi all, I was wondering if lightning the flywheel is worth it or not on a jet boat with a v6 3l essex engine in it, I have facilities to lighten it but not sure if will affect engines performance through jet drive or making engine stall


Thanks

 

[JustJason]

Re: Lightning the flywheel worth it?

Jet drives are a little bit different than IO's or IB's. But with marine engines in general you want them to be able to idle as low as possible when in gear in order to give you maneuverability in tight quarters without the speed. If you lighten the flywheel to much the engine might not hold a proper low idle. You would be the one doing this, and it would be a lot of trial and error on your part. But personally I would not do it.

 

[Ned L]

Re: Lightning the flywheel worth it?

Raceboats typically will run just a ring gear (basically for the starter) so they don't have to put the hp into spinning the flywheel, but as has been said they don't worry about idling. For pleasure use you probably will NEVER see the difference.

 

[damianfishy]

Re: Lightning the flywheel worth it?

Thanks for all responses decided not to do it as it could cause problems thanks

 

[Walt T]

Re: Lightning the flywheel worth it?

The flywheel is there simply to keep the engine moving in between firing strokes. It's designed to be as light as possible and then it is balanced. That's why it's always a heavy mudda, it has to have the centrifugal force to overcome all that friction of 6 cylinders and their rings trying to stop the motor in the brief time between firing strokes. Diesels have massive flywheels to overcome the high compression they use. Once had one crack and break apart because the driver ignored the obvious noise, feel, and poor performance of the two clutch plates grinding on it. It took out the Road Ranger transmission bell housing and embedded itself in the floor board about 6" away from the drivers foot.

 

[JustJason]

Re: Lightning the flywheel worth it?

It's designed to be as light as possible and then it is balanced.

I can't say I agree with that. There are benefits to having a heavy flywheel. Flywheels store energy, and the heavier your flywheel the more energy it can store. Only racing flywheels, where an engine is at constant high rpm, and the vehicle almost never stops. Stored energy is not a concern, so they have lighter flywheels to allow the engines to spin up faster. But heavier flywheels help an engine maintain torque. And this is especially true when there is a tremendous load on an engine. (such as a marine engine). At low speeds, the engine will have a hard time idling, and therefore will need a higher idle speed. Which also means your going to have a faster boat speed. Which you don't always want especially when you are navigating channels or marinas. Or trying to back up 300 feet in a straight line in the wind and current. Conversely, if you are at cruise rpms, having a heavy flywheel will help keep the engine from bogging down when the boat travels over waves. And another way of saying that is it will help maintain both torque and RPM through a rapidly changing rpm.

Heavy flywheels have benefits. Especially on high load engines.

 

[Walt T]

Re: Lightning the flywheel worth it?

I agree. Too heavy though and you can get run on pretty easy. It has to allow the engine to stop too. Its an engineered weight I should have said. Light as possible would indeed be incorrect.