1979 Mercury 115hp ???runs great not in water,

I am having a problem with my outboard, it starts up fine and runs fine in neutral. the other day i was out trying to get up on plain and i could not i opened it up full throttle, and it would go a little bit then act like it is flooding out then it would kind of pull out back and forth like that. so when i got it out of the water i started it back up and put it in gear and everything was fine...i've had one suggestion that it could be one of the sparkplugs fouling out, and thats why it works fine out of the water, but in the water it has so much of a load on it that its fouling out...ANY Suggestions to my problem????

Re: 1979 Mercury 115hp ???runs great not in water,

I would guess the it is one of the power packs . had the same problem with my 115 turned out to be the second stage in the one pack would not advance to get high rpm when under load in the water.

Re: 1979 Mercury 115hp ???runs great not in water,

No load an outboard may seem to run just fine on the hose, once in the water a dead cyl will not allow the motor to perform much at all.

You need to test spark on each cyl using an adjustable gap spark tester set to 7/16 inch. You need to see a hot blue-white arc, any less and the motor will not perform well under load. Any cyl(s) witih no spark will need further testing to determine which component is at fault.

Do NOT assume any parts is at fault and start replacing any parts without thoughly testing to prove the fault, there is NO RETURN on electrical partss, and some can get $$$$$.

CDIElectronics has an excellent Ignition Troubleshooting Guide available for free download on their Support pages.

Repost your findings and any further questions.

Re: 1979 Mercury 115hp ???runs great not in water,

Have you checked the compression? If not, this is the time to do it. Numbers should be 100PSI + and fairly even