WELCOME TO RIVER DAVES PLACE

FLYWHEEL QUESTION.

BDOUCET

Member
Joined
Nov 21, 2021
Messages
13
Reaction score
27
I'm building a new, internally balanced BB Chevy for the boat pictured in my profile pic. I will need a new flywheel and balancer. Is it better to have a heavy steel flywheel are a lighter aluminum unit? I know the lighter parts will accelerate quicker, just not sure about gain are loss in speed. Engine will make around 640 HP. Thanks
 

obnoxious001

Engine building character
Joined
Dec 28, 2007
Messages
6,464
Reaction score
3,815
For a larger boat that you will be "cruising", regardless of cruising speed, the heavier flywheel will do what it's designed to do,, keep momentum up, so that if you let off the throttle for a moment it should be a smoother transition to slow down and also come back to speed. That was the thought process with the water ski race engines that I have built, dating back to when I was building for GT Performance. I can't see your boat clearly, but an outdrive boat nearly always (or always) runs a heavy flywheel with a drive plate on it.
 

FreeBird236

Well-Known Member
Joined
Apr 21, 2012
Messages
13,419
Reaction score
12,041
For a larger boat that you will be "cruising", regardless of cruising speed, the heavier flywheel will do what it's designed to do,, keep momentum up, so that if you let off the throttle for a moment it should be a smoother transition to slow down and also come back to speed. That was the thought process with the water ski race engines that I have built, dating back to when I was building for GT Performance. I can't see your boat clearly, but an outdrive boat nearly always (or always) runs a heavy flywheel with a drive plate on it.
Hey obnoxious, I was wondering if this would hold true for a jet. Way back in the 70's I switched from a steel flywheel to a flex plate, couldn't tell if it was actually faster, seemed like it might have been a little quicker, definitely revved quicker on the trailer.
 
Last edited:

obnoxious001

Engine building character
Joined
Dec 28, 2007
Messages
6,464
Reaction score
3,815
Hey obnoxious, I was wondering if this would hold true for a jet. Way back in the 70's I switched from a steel flywheel to a flex plate, couldn't tell if it was actually faster, seemed like it might have been a little quicker, definitely revved quicker on the trailer.
Most jets that I have seen run a flexplate. Maybe because they are not dragging a prop in the water that acts like a brake.
 

rivermobster

Club Banned
Joined
Dec 28, 2009
Messages
56,090
Reaction score
53,029
Hey obnoxious, I was wondering if this would hold true for a jet. Way back in the 70's I switched from a steel flywheel to a flex plate, couldn't tell if it was actually faster, seemed like it might have been a little quicker, definitely revved quicker on the trailer.

That is the whole point of a lighter flywheel, so the engine can accelate quicker.

Never really thought about how less mass would affect a boat though. I would guess the lighter, the better?

Not sure how about that theory though. Just a guess.
 

obnoxious001

Engine building character
Joined
Dec 28, 2007
Messages
6,464
Reaction score
3,815
That is the whole point of a lighter flywheel, so the engine can accelate quicker.

Never really thought about how less mass would affect a boat though. I would guess the lighter, the better?

Not sure how about that theory though. Just a guess.
Nope, you don't need a lake boat or ski boat to stop on a dime, much smoother with a bit of weight on it.
 
Top