have a 1979 115 evinrude that bogs down from time to time. thought it was fuel tank & line, relplaced both new. had carbs cleaned and rebuilt. engine put on dyno had full compression and great electric on all cyl. took it out for first time this year, had trouble starting, once it got going, same prob. brought it back to mech. now half comp. and low electric. was running perfect b4 dropping. new plugs, stator fine. can't figure it out??? has to be minor electrical because firing on all cyl. then 2, then all, then 3, all, etc. any suggestions would be greatly appreciated. thanks in advance!! keith