1988 Merc 115 HP dropping a cylinder

[walterV]

Hi, I have a problem with my mercury 115 HP in line six, running wide open at 4100 rpm's for several minutes then I hear and see the rpm's run up to 5000 rpm's.<br /> The speed shows about 40 at 4100 rpm's with throddle wide open, and speed about 46 at 5000 rpm's. It idles great at 1100 rpm's and runs great. I had the carbs rebuilt, fuel pump and water pump rebuilt. A friend told me it sounded like one of the control boxes was dropping a cylinder and then picking it back up. Do you think this could be the problem? If so how do i check to see which one of the two control boxes it is?<br /> Thanks, Walter

 

[emckelvy]

Re: 1988 Merc 115 HP dropping a cylinder

Might be that, also might be a cracked coil. ADI's are infamous for eating stator windings, and cracked coils. I have loads of cracked coils in my garage! lol<br /><br />Try running it on the flusher at night and look for sparking/arcing. You may want to pull each coil and inspect for cracks.

 

[walterV]

Re: 1988 Merc 115 HP dropping a cylinder

Thanks Ed Mc,<br /> I will check that tonight. If i find a cracked coil, do i replace the cracked one or all 6 of them?<br /> Walter

 

[walterV]

Re: 1988 Merc 115 HP dropping a cylinder

Ed Mc,<br /> What is ADI's?<br /> I pulled the coils and checked for cracks and found none. I didn't see any sparking or arcing. What do i do now?<br /> Walter