1979 Merc M115 wont stay running

Hello, First post here. I have a 1979 and 1/2 Merc M115 straight 6. I think prior to 1979 it was called the 1150. It has been running fine, until last week. It started up fine to get it off the trailer, but when I pushed up the throttle once on the lake it sputtered and died. Since that time it will not stay running. It will fire and run for about a second, then die. I have checked the #2 and #3 plugs and they both have spark (assuming the others do as well). And I have tried pumping the ball while trying to start it to rule out the fuel pump, and that doesn't help either. I removed the bottom carb to see if any trash had gotten into it, but it was pretty clean. Any ideas what could be going on here? I'm kind of afraid it might be one of the power packs, but hoping someone has a better idea

Thanks in advance!
john

You need to check for spark on all 6. If one switch box is dead it won't run.

Jeff

fastjeff said:

You need to check for spark on all 6. If one switch box is dead it won't run.

Jeff

Click to expand...

Thanks for the reply! OK, I checked on all 6, and all 6 have spark, but #5 is weaker than the rest.

racerone said recently that you should see 7/16 in spark, if #5 has that then I wouldn't worry about it a lot.