Reply To: Johnson FD-12 Won’t Run

[Bob Wight]

OK, so I found a bypass cover with a fuel pump port off a 1960 18hp and installed that along with a Sierra square fuel pump.   Motor will now stay running but sneezes and coughs at mid-range speed and no amount of fiddling with carb adjustments seems to make a difference.   I think the problem now might be the fact I re-used the old ignition coils.   They tested good on the meter and initially seemed to put out a good spark with the plugs in free air, but I think I may be losing good spark under full compression load while running.   Here’s a Youtube video:

https://www.youtube.com/watch?v=SFCkzKldlhM

I did manage to get one pretty good run after this one where the motor ran pretty smooth but then died out at the very end.     I pulled the plugs after testing today and you can see in the attached pic a big difference in the plugs with the bottom cylinder heavily oil fouled, so that makes me think I’m losing spark.   I tested the plugs in free air again after removing them and although they put out a spark, it’s not a hot blue spark, more yellowish-light blue.   And FWIW, these are brand new NGK plugs.

Comments welcome.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
1982 Evinrude 25hp

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."