I replaced my worn Merc distributor this year with a Marine D.U.I. and I picked up about 200 rpms. I can't say for sure if it was because the old distributor had some play in the shaft or if the D.U.I. just works better. I am pleased though. Nice clean setup and the price is right.

Mac dad, do you have stock motors and what ignition module were you running from merc.

Also is there a way to adjust for diffrent deck and manifold heights on the dui distrbutors to get the proper lash on the distributor gear.

I think there is enough evidence here to say MSD boxes are problems. When I was into cars, folks had the same problems. Besides, the multi-spark only works at low RPM. I would not get into anything that used an MSD box. If a system is roubust, you shouldn't have to carry a "spare". I'll get assulted, but factory or modified factory (changed timing) work best for me.

I wonder why there are two MSD boxes on the dash to get through a three hour race??? Anyone watching all the Nextel Cup races this year will have seen more than one or two go South