Mercury 40hp sputters at high ok at idle

[pat]

" I have a 1984 40hp merc OB t

" I have a 1984 40hp merc OB that has had this issue for years. Starts great and runs fine at max speed for about 300 yards at which time the engine starts to sputter. I throttle back and run at idle for about a half mile and then all of a sudden I can throttle up and the engine works fine for the rest of the day. This happens all the time and has been repeatable for the last 5 years. I have changed out all of the fuel components, but some how think this is an electrical problem. Anyone have some thoughts ? "

 

[tonyob]

"Pat,

I have never come acr

"Pat,

I have never come across a problem exactly like yours, but have seen a few similar ones. I would guess that there is a problem with either the stator or trigger coils.

Tony"

 

[TWIN BRIDGE MARINA]

YOU HAVE AN INTERMITTENT SPAR

YOU HAVE AN INTERMITTENT SPARK PROBLEM. RUN THE ENGINE AT NIGHT TO SEE IF YOU CAN SEE SPARK JUMPING ANYWHERE. CHECK FOR LOOSE GROUND AT SWICH BOX AND COILS. WHEN IT RUNS ERRATIC REMOVE ONE SPARK PLUG WIRE AT A TIME TO SEE WHICH CYLINDER IS CAUSING THE PROBLEM. TEST THAT COIL AT A DEALER. LAST RESORT IS THE PROBLEM IS INTERNAL IN THE SWITCH BOX. CAN BE VERY AGGRAVATING. GOOD LUCK....BRIAN

 

[heinz]

" WAIT!!!!!!!! Sounds like you

" WAIT!!!!!!!! Sounds like you have same motor as me!!! Can you describe/post pics of it? I'm trying to get manual(s) and as much info as possible on it. Probs. I discovered this week(wouldn't start) were.....#2(lower) sparkplug wire was arcing on block(taped it up w/ electrical tape), look under ignition module(2 bolts hold it in), I found LOTS of corroded wires that I re spliced w/ new. I also installed in line fuel filter(cheapy) in fuel line before bulb and swapped out old gas/premix w/ new - what a difference, now she screams! I'm still planning on replacing ALL engine electric wiring. Where is Serial #???? Let me know any info, maint. hints etc. I'm a good mechanic but this is my first boat and experience w/ 2 strokes, Heinz "