More timing at idle will help with big cams and a rough idle. Your cam is nothing radical that would require that much timing at idle.
20* at idle is more than enough timing for a 540 with a 741 cam. It should idle at 800rpms or less in gear easily.

I use MSD Starter Savers, automatic retard for starting. And Tilton high torque starters. Otherwise Jeff is right, you wouldn't like them locked out. I was losing a starter a week.

I tend to build a dist for your style of application with 14*to 16* total. This allows 34 to 36 max and 18 to 20* BTDC base.
Hold off any advance until 1500 to aid in cold running and then ramp up to full advance from 1500 to 2500. Absolutely "all in" by no more than 3000.

sounds pretty good. thanks for all the input guys.

I run mine locked because the idle is so much better. It was hard on starters and acteally broke the ring gear loose from the flywheel once, but i put the starter savers on and have not had any problems since.

You can lock out your distributor and use this product to get most of what Airpacker stated. I like the high rpm retard feature. Say you normally run 92-93 octance and your boating in a different area and only 87-89 octane is available. You pull out the 0 module "pill" and insert let's say a 4 pill. Presto--------you now have 32 degrees of full advance (if your total was 36 with the 0 pill).

The timing control provides for a nice controlled ramp-up on the timing advance as the rpm increases.
Disclaimer: Must be used with the MSD ignition control. I.E. the #6M box for an example.
http://www.msdignition.com/Products/..._Computer.aspx

At a minimum, what PatriYacht wrote-----use the MSD starter saver unit.

Do you have to have a MSD Dist. for the starter savers? Or can it work right off the box I would guess.

Rotax
For the timing controller does it require a Dist. for that?
Im about to buy a MSD box, just debating which one since some people have had bad luck with the MSD Marine units.

Yes on the distributor. I would recommend this MSD billet distributor as a short cut to what to use. However, I don't like the moveable slip collar.
http://www.msdignition.com/Products/...stributor.aspx

On the Starter Saver, it does also require you to use the MSD marine ignition control. I am not going to deny that several OSO members have had these go south. Still, IMHO the best at what it's does. Do a search on the NET, I believe there is a company that does service the #6 boxes and upgrades them. Here is the newest #6M box with rev control.
http://www.msdignition.com/product.a...ine%20ignition

ALWAYS BUY TWO of anything MSD and keep the spares on the boat.
When I used to use MSD stuff, I had a second 6ml box bolted right on beside the one in use. Unplug the dead one, plug in the other one. Order another new one. I don't like drifting.

Of course, the other issue I have with MSD distributors is that no matter what, they always seem to end up a ball of rust under the cap.