89 Johnson 40 will only idle

[kayladog1]

My motor has been acting up intermittently by not reving up. It will start and idle fine, but try to throttle up and it starts missing & bucking. Sometimes it will do this for a while then suddenly rev up ok. Doesn't matter if hot or cold. Its a 1989 Johnson 40 hp VRO Model CJ40ELCEC.<br /><br />Changing plugs makes no differrence. If you pull off a plug wire it seems to run smoother on 1 cylinder. On 2 cylinders it seems to buck like mad like its firing at the wrong time. Has spark to both plugs. Tested it in the dark. No arc between wires. How can I tell if its the powerpack acting up? Or maybe it the carbs. It really stinks & smokes when you apply throttle, but I can't tell if its missing or getting too much gas

 

[Waterbugtoo]

Re: 89 Johnson 40 will only idle

Is it firing at the right time? Power pack could possibly be double firing. That wouldnt be good. The quickest way to check would be marking the edge of the flywheel at TDC of each cylinder with whiteout. Start motor and speed up to the point it acts up, check each cylinder with a timing light. Does the mark show up where it is suppose to at the pointer for each cylinder? Does either cylinder fire at any point other than at close proximity to timing pointer?<br /><br />

 

[rickdb1boat]

Re: 89 Johnson 40 will only idle

Check to be sure the timing plate is moving freely. Sometimes they stick and won't advance the timing as throttle is applied.

 

[Walker]

Re: 89 Johnson 40 will only idle

Also clean all you coil grounds.

 

[Offshore Fishing]

Re: 89 Johnson 40 will only idle

Don;t forget the three rules......<br /><br />Spark, Compression, Fuel,<br /><br />Be sure to check all connections for the coils including the harness plugs (terminals) It happened to me.<br /><br />Compression Guage, Borrow Beg or Buy<br /><br />If all checks out above Clean the Carb(s)kits are cheep just don't spray the outside surface, Dirty carbs has kept me off the water before. pay close attention to the float and valve, spring and seat... Good Luck

 

[rickdb1boat]

Re: 89 Johnson 40 will only idle

Imagine That has good advice on the Carbs, if that turns out to be a problem. Definitly check the connections, also.

 

[KennyKenCan]

Re: 89 Johnson 40 will only idle

One other thing to check, make sure the plug leads from the coils are going to the correct spark plug. Something that simple can make for a bad day.