I have a 1991 454 Mag with Thunderbolt IV Ignition. I called Merc and the tech said there was not a Rev Limiter built into my ignition. My question is whether I can just add a MSD Soft Touch Rev Limiter to my existing ignition or do I have to buy the complete MSD ignition? If I can purchase the Rev Limiter only, is it an easy install. Thanks

You have to use PN 5468. I have the wiring diagram somewhere, I'll scan them when I find them.

YES. I am using one with the T-Bolt IV and it works fine. However, the one I have was nasty to set the limit on. Hopefully, they have improved things in that area. Sorry, I can't get to any pt.#'s till more snow and ice goes away and I uncover for the upcoming season. --- Jer

Setting up a friends boat with the same problem. We want to increase his rev limit to 5000. Any new info on this set up. ie part numbers and results? How easy is the hook up??
thanks

The MSD BOX I purchased had the rev limiter built in to the box. All you had to do was swap out a little plug type module with whatever RPM you wanted. Each plug had the MAX RPM printed on it. MSD sells a RPM kit with about 6 different RPMS. For example 5000 RPM - 5700 RPM. Basically for whatever RPM you wanted

Autozone now stocks rev limiter chips for msd in various rpm ranges.

Can you still use the stock merc distributor? Do you have to do anything to the merc distributor so that the original rev limit won't inter fear?