Originally Posted by dbkski

The early 90's EFI engines used a different flame arrestor, such as you pictured, and will not work on your 1998 502. If you have the
serpentine belt set-up like my 1999 502 then you need the style below. The two styles of flame arrestor mount differently.

http://www.knfilters.com/search/prod...x?prod=59-4542

I got my assembly from Dana Marine years ago. I did some testing and lost 9 RPM's at 5000 RPM's using the K & N filter.
I bought the assembly for better filtration since we have a lot of bugs and cottonwood trees around my area.

Originally Posted by dbkski

What?????

As stated earlier my engine is a stock 1999 Mercury 502 Mag MPI. I tested with the stock flame arrestor, none, and the K & N.
Using the stock one actually allowed for the highest RPM's but since the numbers were so low I consider it insignificant.