I have recently upgraded my 330 hp 454 with new heads, cam, intake and carb. the cam i'm using required me to speed up my idle to about 950 rpm's, but the factory 1997 Merc. dist. has the timing/ adv. control built in and wants to keep idle at 800 rpm instead. I replaced the dist. with a car HEI unit I had and it works ok, but is there something better with advance curves designed for marine use? The thing seems to be happiest with 30 degrees of total advance.
If anything it may be a little sluggish getting on plane but really comes on from about 2500 on.

These are great marine dist. Buy them from Triad marine.

http://www.performancedistributors.com/

I agree with Boatman, The D.U.I. distributor's are great! Nice wire sets too.

If the engine doesn't come alive until 2500 RPM, you may have "over cammed" it for your application.
In my Olds 442 I have an Edelbrock Performer RPM that is so flat under 2500 that I needed a stall converter to get it to launch correctly.
In a marine application you really need a cam that starts pulling off-idle.