I have a 1985 Mercury 90 HP inline 6 cylinder, I have had this boat a little over 4 years, carbs cleaned and new water pump in the spring of 08 no problems since, until now, last week I went to the lake and was driving slow through some stumps and all of a sudden I lost 2 or 3 plugs sounded awful, anyway I went on and fished a while, and I started it up and it was fine for a little while, and it fouled out again, then I got to open water and got to give it some gas and it finally got ok, then I stoped and fished again and started going and it fouled again, it got better before I got to the ramp.
I got home and bought some plugs, went to the lake this weekend and it was fine, then it happened again when I was going slow, after I started going faster it got better, and really runs good at high speed when not fowled out!!!

Now I am not a boat mechanic, and am really dumb on boat motors, but it just seems to fowl out the plugs, and acts to me like it is not getting enough fire at low RPM's!!!

Can anyone help me out???

sounds more electrical to me like the coils or power pack ask opti

are there a way to check the coil or the power pack???

sounds like switch box, breaking down, thats like a power pack on a johnson or evinrude. Also there is a stator and a trigger involved. Unfortunately it takes a DVA meter to fined out. You will probibly have to have a tech check it out.

Thanks, I appreciate it guys!!!

What kind of money would it take to have this checked out???

I went out again today, and it started doing it again, it seems to do this after it is warmed up, and you are going pretty slow, it runs good fast, but after it starts cutting out, it takes a little while before it starts running right again, but cold it seems to be fine!!!

that definately sounds electrical in my opinion

call cedar valley college in lancaster they have a outbord program and maybe they can check it out ask for duncan paul

Do you know of anyplace closer to Denton, I try to not even go to Dallas, and laLancaster is way on the other side of it!!!

Call Marc...he is in Fort Worth. Honest and the best Merc mechanic around. He has been in business 30+ years.

Gunter Marine
2243 Jacksboro Hwy
Fort Worth, TX
(817) 626-5693‎

Larry,

I know a guy just west of Denton that can fix you up.

Call me.

CW

That inline 6 has the same ignition system as the V-6 engines. It is a possibility that the stator is breaking down and now supplying enough power to ignite the plugs correctly, But, my 1st look would be at the air/fuel mixture screws and the linkage between the three carbs. Also take the cowling off and see if one of the carbs, is lightly flooding. That will do the same thing as what your talking about. Flood out at low rpm, run big time at high rpm.............Worth a check before a drive.

Thanks to all of you, I will look at my carbs, I had a cracked float one time and it kind of did that too, and used a whole lotta gas! But this time is different, it may be flooding too though!!!