Ive always had msd 6m-2 boxes wired in with my stock 500hp distributors and now i have did away with the stock distributors and added msd distributors wired in to the 6m-2 boxes but there is a single gray wire off the boxes for tach will i need to hook that up now that i dont have stock distributors and if so how do i know what wire from the merc harness.

Thanks

There should be a brown wire connected to the negative side of your coil. This wire runs to your tach. Disconnect it from the coil and connect to the gray wire from the MSD box. This should have been done before when you originally installed the MSD boxes. It may have been hooked to the distributor I don't know but it's the solid brown wire you want to connected to the gray wires only.

my coils have only ever just had the orange and black wire from the boxes no other wires and tachs worked fine. the only wires not hooked up now that was with stock set up ie the 2 that went to the stock dist. Also wondering what is the module looking box under the macatharode on the back side of the plate bolted to the rear of the head. was that a rev limiter or is the limiter in the stock dist.

anybody know

nobody has changed to msd from stock that knows where the tach wire is or do i have to run a new one back from tachs.

I connected my tach lead from the engine harness directly to the gray wire from MSD box. Do that and it should work fine. I even used the MSD weathertight plug.

how do i know what wire is tach lead in harness.

I dont have my wire diagram right now so I cant tell you color. You can always check back of tachs to locate correct color. Ill try to post it later. Gotta work on boat later.

Maybe someone can chime in if they know the color of wire.

where would it of hooked to with stock set up, so i know where to look for it.

Hey check this out should be alset
http://www.jegs.com/InstallationInst...1/121-6460.pdf
-Mike