I have the 7.4mpi and have the same soot problem heard the msd ignition does help, I fill up at the dock usually but sometimes on land. 89at the dock, 93on land. Never noticed a difference with either fuel and alot of the stations up here get there fuel from Green Bay, I just clean it off real quick when ever I have the boat on the trailer. Although our soot problem is minor if you compare it to my dads diesels.:rolleyes:

In the Marine field usualy you can not hear detonation because of the water cooled exhaust, but when I put some Ft lauderdale petrol in my boat,I juiced it once or twice and heard a slight detonation, wow, this has never happened before.
cheap ass swamp gas I bought in Florida.
This was so called 93 Octane also. Yeah right!!.
My boat never labored before untill I hit the big
pond we call the Ocean, wow, I could loose 5 knots in a swell cruiseing to the Bahamas. But the trip back was cool and fast & intense. :cool: :D :eek: