I have a 15 hp johnson outboard. It turns over good, but is not firing on either cylinder.What should I try?

Question

The motor was given to me. The person who gave it to me knows nothing of the condition, and got the motor from an aunt whose husband had passed away. The moter has been well taken care of and is very clean under the cowl. I hooked a battery and gas to it, it turns over really good. I changed the plugs and checked the fuses. It does not seem to be firing. I would appreciate anyone who could tell me what to try next.

Answer 1

Remove the sparks plugs and ground them to the engine, roll it over and see if there is spark. (white or bright blue - not yellow). If none or weak (yellow) then you need to check under the flywheel, points, or if a later model, the trigger coil.

Be sure if there is a red switch (later model) on the front handle that the plastic spacer is in, (lifting the switch to break contact) otherwise the switch is in short mode (stop mode - grounding spark to motor).

If good spark, put a small amount of fresh gasoline in each cylinder, while the spark plugs are out, replace plugs and try to start,  if it fires, and or runs, then stops, you need the carb cleaned, if it continues to run, problem solved.

NOTE: make sure you have water hooked to the bottom end water intakes, either with ear-muffs, or with the bottom in a tub of water a couple inches above the fin, or you will most likely have to replace the water pump impeller.

Answer 2

make sure you have spark.

spark checker you can get at automotive parts store.

their cheap..8 bucks or so.

if you don't have spark,..you now need to check your ignition system. You can do this with a volt meter.

if you have spark...and it still isn't starting,...then it's a fuel issue. check to see if fuel is getting into carb.

Disconnect fuel line after the fuel pump. Crank engine and see if fuel is pumping.

If it's not you could have a clogged fuel pump or something.

Okay,..good luck and you better give me my best answer kudos as I had to bother my marine mechanic hubby to get this answer!!!  LOL.   Good luck  :~]]

Answer 3

If by "Not firing"  you mean that there is no spark on both cylinders,  high probability is the points are corroded shut.  The points are under the flywheel.  Pull the flywheel and check them.  If they are stuck shut, you can gently pry them open - then clean the surfaces with a small file and set the gap.  Then replace the fly-wheel and it should be generating a spark.   I would also change the fluid in the lower unit and  you should be all set to go.

Answer 4

If the motor has been setting for a while the carb is probably gummed up. You can usually smell the old fuel if this is the case. I dont know what year your motor is but a spark issue is normally caused by the points on older models or the power pack on the ones that are equipped with one. Check the spark first, but I have cleaned dozens of carbs from outboards that just sat around too long. If you get it running be sure to check the lower unit oil before heading to the water. Any milky looking oil is sign of water leaking into the unit and should be resealed.