so, K&N filters are now CG approved spark arrestors?

Not all of them. Just the ones that are "marine flame arrestors". They have been available for over a decade and carry the proper identification as such.

Correct.

Here is the FA section: http://www.knfilters.com/marine/boats.aspx

Thing that stinks even with their round FA's, you cannot purchase just the element when the time comes you want to replace them. You have to buy the complete assembly.

People think K&N's are lifetime. Well, they are not. They shrink over time ! Yes, seen this happen many times in my professional and personal life's. Doh !

And yes, I would use a 14" x 4" element on the motor in question. If you want to go larger, that is fine.

I have not seen positive dyno runs with the Velocity Stack assemblies.

The 9X4 assembly has a 2.75" element height and I have a mid to upper 300hp small block motor in very light weight boat that loses almost 2mph with this assembly. The Demon carb installed does have a choke tower.

Anyone have numbers on the metal flame arrestors? One better ten the other. Just looking for the best options.

That velocity stack w 3x9 element was the hp killer in our dyno testing, we also clamped the element and lid on full size base to see IF it was the velocity stack or elent, it was the element that killed hp, too small of area

Not too off topic. What's available with a dominator base?

A decent amt.

If the arrestor doesn't come out and say it's for a Dominator (4500 style) carb, look for 7-5/16” flange diameter.

Good to know thanks. I'd like to get one of the nice radiused k/n bases and put an arrestor style top screen on it

The ones on my 500efi's look like they are collapsing/shrinking and was wondering about that. Maybe if that was restricting air flow. I guess its time for new ones. The 525's seem to be bigger will they would on my 500's?

Yes, the K&N's shrink over time....and yes it is restricting some airflow.

I have one here that has shrunk more than anyone can believe, until I show them.