78' merc inline 6 115

[Dassault]

Hello,
I have a 78' mercury inline 6 115. This boat runs great with new plugs, a true monster. However, after only a few hours of running, such as two 2 hour trips, the plugs begin to foul and the boat stuters and fouls when trying to plane out, obviously not allowing me to plane. I have decided that it may be a ignition issue, maybe? Maybe there is a weak spark, so i have begun to clean the cap and rotor, removing the corosion that could be the problem. However, could this also be a fuel problem? Maybe a float adjustment, if so how would i go about adjusting the float levels? I have tried ever mixture setting known to man, running 50:1 gas to oil. Over the past few months I have rebuilt the carbs, fuel pump, replaced bulb, new plugs and fuel lines. Any ideas?

 

[Laddies]

Re: 78' merc inline 6 115

A dirty cap and rotor usally cause a missfire as does a worn carbon in the center of the capm, usally a fouling problem is a rich mixture, inlets, low floats or a bad fuelpump diaphram

 

[tashasdaddy]

Re: 78' merc inline 6 115

your carbs need work and you probably need a linc n sinc. do you have the engine specific mercury manual for yu engine. if not get one. oldmercs.com

 

[Dassault]

Re: 78' merc inline 6 115

What is a linc and sinc exactly? Yes I have a manual. The carbs are completely rebuilt, with the exceotion of the needles which showed minimal, if any, wear. I wouldn't think that i need to adjust anything if i haven't touched anything but the carbs and fuel system.

 

[Plainsman]

Re: 78' merc inline 6 115

linc and sync sets up the carbs and the timing to work together. This is from clams:

http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=36;gtid=1114512

 

[Clams Canino]

Re: 78' merc inline 6 115

If you do a lot of trolling.... then your idle mixtures are prolly set too rich. The thing should NEVER foul plugs cruising at 4000 unless there is a pretty obvious problem with the carbs or fuel pump.

-W

 

[Dassault]

Re: 78' merc inline 6 115

The plugs don't foul out 4500 rpms only when idling for a moment or so. Then, bogs down and fouls, then planes, then clears out, stop and idle and same scenario all over again.

 

[Dassault]

Re: 78' merc inline 6 115

Sorry if im not clear, it only does this after idling for a moment or so, i use the boat to ski. Once I get up on plane it clears out and runs like pretty well. But thats hard with a skier so it has to be running almost perfect to ski, which it usually does. Two weeks ago it ran like new when i put new plugs in, now its hesitating and fouling again.

 

[tashasdaddy]

Re: 78' merc inline 6 115

clams the in line expert,,to rich at idle, the link n sinc. really helped my 71 inline 1350.

 

[Dassault]

Re: 78' merc inline 6 115

what about float level adjustment? Is that a common adjustment on these mercs, that seems like it could be a problem, to much fuel going into the carbs. I still can't bring myself to believe that i need to adjust my linc's, but who knows guess i'll give it a shot this weekend, but any info on float adjustment would be appreciatied.
Thanks for all the info,
Dassault