What is a good plug to use on a '98 7.4 MPI. I believe it recommends to use MR43LTS but I am getting a fair amount of black on the transom. I was wondering if I could use the MR43T, R43TS or the Champion RV15YC4's.

Thanks,
JBH

I have run mainly 87 but I have put a tank of 89 in and it did the same thing.

My only concern is that all the info I can find is that the 7.4 MPI uses a completely different plug than the 454 MAg and 502 MAG MPI. I would like to try the R43TS to see if it helps but I don't want to damage anything since this is a different plug type compared to the R43LTS.

use a 44 lts something warmer to help burn the black unburned fuel /add a MSD 6AL?

bobby,

What would the 6AL do other than give a stronger spark. I know with this unit it has multipal sparks but is that it? If I add this will I have to do anything to the computer?

sixpak;

I added an MSD 6M-2 last season. It cleaned up my transom alot. No more soot!! You don't have to change anything else due to adding an MSD.

Yep like check mate said just buy a 6 AL and Blaster 2 coil from summit and it goes on and really will help .. The multe spark I think is what really cleans up the idle and in some cases will give some ,some top end mainly it helps driving and the transom
Also open the plug gap to 40 k with the MSD ,,
I use them (6al) they are exopy filled and work great in a boat and save money over the 6M --look at there web site alot of good
info

The black on the transom is unburned fuel I think this will help