Help!! 1971 Mercury 115 hp outboard having trouble running

[83Baja16ss]

Hey everyone, I recently swapped my 85 hp evinrude out for more power in a 115 hp inline 6 mercury outboard from 1971.
I started it saturday it ran perfect, couldnt let go of the key fast enough to start once it was warmed up for a minute. I let it run for 8 mins or so pisser did not get very warm, but I was satisfied with how it was running, quick revs on the throttle were super responsive, not a misfire at all.
Took it out on sunday for maiden voyage warmed it up for a minute and it ran great, got it up on plane and it had tons of power very smooth 3/4 throttle or so and then it started loosing power, misfiring and just plane no throttle response like the cable want opening the carbs and then stalled. I limped it into shore and took it out a hour later, it idled well again and when I applied quick throttle it would have full power for a second but when the revs got around 3000rpm or so misfires.
I hit the choke when it was missing and it would almost stall so I dont think it is fuel related but just looking for some input from you merc power tower gurus ohh it has great compression and new plugs, distributer looks old wires look good but old, and ground wire from distributer to block is heavily deteriorated(replacing this today) anyway any ideas to send me in the right direction? Thanks

 

[83Baja16ss]

Re: Help!! 1971 Mercury 115 hp outboard having trouble running

so today i started it up with the cover removed it ran well just like before, noticed a fine mist from a fuel pump hose that goes to the block, that bad ground wire that I'm going to replace, pulled the distributer cap found a bit of corrosion, plug wires will not come out of the cap so I'm just going to replace those and the cap and rotor, also noticed the terminals on the stator are rusty, Im thinking about replacing that and the belt for the distributer is a little loose. are there any other things I should check/ replace while I'm in here? Any input on my situation would be greatly appreciated!

 

[hoosiercaver1]

Re: Help!! 1971 Mercury 115 hp outboard having trouble running

U may know, but in case u didn't the spark plug wires actually thread into the distributor cap. They don't just pull out like most do on other motors. Just tryin to save u some trouble. I have a 1970 115 that I'm workin on too. I hope we get these runnin like dream!

 

[83Baja16ss]

Re: Help!! 1971 Mercury 115 hp outboard having trouble running

Hahaha I did not know this hence why I could not pull the wires out of the cap! Thanks a lot def saves me some trouble! Good luck with yours hope they are running soon next step buy a manual haha

 

[hoosiercaver1]

Re: Help!! 1971 Mercury 115 hp outboard having trouble running

No problem, luckily my buddy used to have an old mercury so he warned me before I messed up the cap. U don't want to mess up the cap because I think the aftermarket ones are 100$ plus. Hopefully if u get ur wiring in order and it will run good. I know I had to redo alot of my fuel lines cause they were so old the started leaking. U might want to look into that if u r goin through and fixing stuff.

 

[Chris1956]

Re: Help!! 1971 Mercury 115 hp outboard having trouble running

Distributor rotor is not replaceble and real fragile, so don't break it. Clean up the dist. cap contacts with fine sandpaper. Check plug wires for cracks. They can be had for about $6 ea, if you look around. Replace dist ground wire and fuel line that leaks. Rebuild fuel pump. Carbs should have banjo filters under covers on carb cover. Replace these.

Usually wiring harness is real bad at this point in it's life. Check it over for lost insulation.

 

[83Baja16ss]

Re: Help!! 1971 Mercury 115 hp outboard having trouble running

Thanks so much guys this information really does help, I am going to clean the cap and rotor up tonight and order a set of plug wires and a stator since my connections are flaky rust and I'll do the the ignition timing belt while im in there. Did not know about the banjo filters either, I will inspect those as well, and my wiring harness has seen better days, I am slowly replacing the wiring as I go, I'm going to really go at it this winter. thanks again!