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1985 115hp merc skipping at full throttle

S

sullybe

Contributing Member
I have a 1986 Merc 116hp l6 that runs good at idle and 3/4 speed but when I go full throttle it starts to skip, I thought it might be a fuel problem so I ran it off a 6 gal tank it nothing changed. It was running fine the week before. It still starts right up and runs OK until I go over 3/4 throttle. Any help is appreciated.

Thanks Dan
 
I have the 2002 model 115 hp 4 cylinder (2+2 carb setup). It was struggling (coughing like) when I gave it full throttle above 2500 RPMs. I found the #3 carb main jet was partially blocked. I sprayed it w/a shot of "Deep Creep" (Seafoam in a can) and it opened it. I tested it in the river on the trailer and it no longer coughs--throttle response in forward is immediate. The downside of the trailer test in the river; the prop apparently kicked up a stone and nicked a quarter size chip/crack in one of the blades. But, I was lucky to find two reman. duplicate props the local dealer was closing out for $30 each.
 
Hi Guyjg, I don't have any coughing or backfire thru carbs, I run Seafoam in every tank of fuel so I am pretty sure the carbs are in good shape. Thanks for the input.
Dan
 
Put a timing light on all cylinders ( one at a time ) and wind it up in the lake / river.-------------Observe and take notes on how each one behaves.----------------Will help you pinpoint whether ignition or something else. ------------If ignition it will help determine wheter it might be Stator / trigger / coil or one of the CDI boxes.
 
Thanks for the information, I tend to run my engine heavy on the 2 stroke oil so I am going to start with easiest and change the plugs, I have had them in for a couple of years now so they are due any how. The hard part is getting out to the boat with this storm Irene comming.

Dan
 
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