Replacing my 525SC clone with a 540 670hp engine. What type flywheel is best. I was originally thinking I could use flywheel from old engine. But it is a Merc 420 set up balanced by Derberry. and chances are externally balanced and 540 is Internal balanced.

What is best a steel or AL unit mated to a bravo. Which stresses the drive less? Anyone know the weight diference between the two? Any budget but durable brands to consider?

Can I get by reusing bravo coupler I used for 525SC? Or is it necessarry to go to HP coupler that CP Performance sells? Boat is lightweight 230 Velocity.

Unless this is a race boat there really is no advantage to an aluminum flywheel.

Tried to go to aluminum and the boat would flat out not idle in gear. Boats need the heavy flywheels.

How low did your engines idle? Just wondering.

I have them in my boat but they are crash boxes. I saw nothing going to them other than when you bolt them on the crank.

With aluminum, maybe 800 RPM in gear and 600 RPM in gear with steel? Hard to say for sure, as the old automotive Holley Dominators were also part of the idle problems. Today we can idle at 450 RPM in gear without jacking with the throttles or stalling around the dock. We also have a pretty aggressive solid roller valve train.