Stock Flywheel (steel)

[RSM]

What maximum RPM are the steel flywheels safe to run at ? thanks

[STV_Keith]

I have turned mine 7100rpm with no problems.

[CompKing]

My 90 2.4 BP came with a steal flywheel and I ran it 7500+ with no problem.

[Rusrog]

a danger of the flywheel coming apart that is the problem. I think it is the weight of the flywheel causing crankshaft failure. That being said.... I turned mine 8100 without failure.

Good luck,

Russ Rogers
Ft Worth TX.

[Jay Smith]

The HEAVY steel flywheels are safe to turn upas far as intergrity but the havoc they cause to the upper and upper middle main bearing will tell its toll very quickly !

[P Nichols]

Jay, Would it be bad if I were to run a little heavier fly wheel for top end runs only...or should I play it safe and stay light???

Thanks, Paul

[Jay Smith]

Paul ,
We have a saying at JSRE "Light Is Mite". The lighter the flywheel the less power the motor is expending turning the rotating mass and can expend that power turning what we want and that is the prop. Any reduced mass is adventatious to the overall power curve in acceleration.....

[P Nichols]

Thanks Jay, In that case...I'll stay light.

Paul

[Jay Smith]

Hows it doing Paul? Find the electrical Gremlin?

[P Nichols]

Jay, It was the vacuum hose on the ECU...it came off. I must have been running REALLY rich...how many MPH do you think I should gain with the hose on...LOL??? Now I need a new cut down 1.87 pinion gear before I can make another run...do you know where I can find one or do I need to call Dave Stecbauer?

Paul

[xtreme53]

Originally posted by Jay Smith
Paul ,
We have a saying at JSRE "Light Is Mite". The lighter the flywheel the less power the motor is expending turning the rotating mass and can expend that power turning what we want and that is the prop. Any reduced mass is adventatious to the overall power curve in acceleration.....

What would you recommend in an offshore application Light or Heavy.
Would the crank not be put under more strain as the boat leaves the water and the rpm raises then on re-entry there would be less revolving mass to keep the RPM up as the prop grabs the water.

[Jay Smith]

I have torn down offshore race motors that started a race in new condition and after one race the top and the upper middle main bearings were shot so bad the blocks were unusable and the cranks after X raying showed cracks and were also discarded.With the off shore motors completley leaving the water and allowing the motor to spin up and hit the limiter with no load then as the motor enters the water and is loaded again would play havoic on the harmonics of the motor from the pinion gear to the top of the rotating assyembly ( flywheel) The more there is a potiential harmonic problem as a bad fit on the crank or worn crank saddles that the lower and upper middle main races fit the more weight is needed to dampen harmonics. The heavier something is in the center of the axis of rotation ( say a flywheel ) the more stable it becomes and is usefull in dampening harmonics. Not to say its faster its just more harmonic resistent.
On the other hand if one has a motor that stays stuck to the water ( Drag Racing ) the motor expends extra power spinning that rotating mass weight during full acceleration and that expended energy could have been used in turning a higher pitch prop the same RPM or the same pitch MORE rpms ! Results lower E.T.'s or more MPH..........

Just my thoughts,

[Jay Smith]

The weight of the flywheel is directly proportional to the the side load that is put on the crankshaft and the bearings . The Mercury motors have miminal bearing strength in their design and the cranks tend to flex , backward upon acceleration and forward during decelleration. Because the blocks are aluminum and of a soft material the saddles become sloppy allowing the crank to move farther and farther out of the center of the axis of rotation or flex and soon the block is mishaped ( egged ) and the crank finally be comes fatigued and will fail or the bearings will give up as it is being run at the bottom staight , being held in place with the block, and flexing at top because of the flywheel gyrating in the not round saddles !

Hell I know what I'm trying to say hope the rest of ya'll know too .....

LOL........

[skydog]

Good info Jay!!
Thankyou Skydog

[xtreme53]

Jay
I have a brand new F1 that I intend to use for waterski racing.
Should I run with the stock flywheel or have it lightend.
The races that I intend to use this motor at will be resonably flat, but the boat will still leave the water occasionaly.
I also have a finger ported XR2 2.0lt carbed motor that has a heavy weight flywheel, I use this offshore but intend to replace the flywheel with a lightweight version.
Will this help the motor to pick up rpm quicker, and could it help with hole-shot and acceleration out of corners.

[Jay Smith]

Our JSRE F/1- Drag Race ultra light flywheels will surley help in acceleration and from pin to pin out of the corners. The offshore thing with the motor leaving the water I would weigh the dampening of the harmonics effects with the heavier flywheel verses the protection of the bearings and block saddles with the lighter. I know thats kinda vaigue but its kinda like saying do I wanna be eaten by a Grizzley Bear or a Great White Shark the end results are the same just one may happen a bit quicker.............