slight misfire/ Ignition? Fuel?

[BigNiner19]

Trying to troubleshoot my problem with my late 80's early 90's Johnson 60 horse. Motor ran pretty good before I removed it for a cosmetic makeover. Ever since I installed it back on, it has been misfiring. I knew my battery cables were old and worn out. So I replaced the power and grounds already. I've got a solid connection there. I don't think the problem is fuel related...but I wont rule it out completely. There doesn't seem to be any specific cylinder of the 3 that are misfiring either. They all did pretty much the same thing while running and testing the spark. The motor sounded alright on the hose, and even sounds pretty normal in the water while in nuetral revving the motor up.

However, while in gear, there is a very noticeable loss in power...the boat cant really even get up on plane. You can hear it popping at real low speeds as well. I put in new plugs, and it did not fix anything. Anyone have some input? The coil? What would make it misfire like this? The motor fires up really good, so I know its getting good power from the battery.

Cory

 

[Silvertip]

Re: slight misfire/ Ignition? Fuel?

Once the engine is started the battery is not needed to continue running. It's purpose is only to operate the starter. That means the battery and its cables are not the issue. Try squeezing the primer bulb or pushing the key in to provide a little extra fuel. If the engine picks up its a fuel delivery problem. If it doesn't help, look at the ignition system. Just so you know, an engine with no load on it may sound normal even though its running on half its cylinders so reving the engine in neutral proves nothing other than its running. If you can't get on plane, the engine is down at least one cylinder.

 

[BigNiner19]

Re: slight misfire/ Ignition? Fuel?

Once the engine is started the battery is not needed to continue running. It's purpose is only to operate the starter. That means the battery and its cables are not the issue. Try squeezing the primer bulb or pushing the key in to provide a little extra fuel. If the engine picks up its a fuel delivery problem. If it doesn't help, look at the ignition system. Just so you know, an engine with no load on it may sound normal even though its running on half its cylinders so reving the engine in neutral proves nothing other than its running. If you can't get on plane, the engine is down at least one cylinder.

Yes I figured that having the motor under no load would make a difference. Im not sure if its down one cylinder or if its just all the cylinders misfiring. I understand that the battery cables probably were not the problem, but they were rotted anyway and needed replaced. I still believe it to be something ignition related however...Its getting enough fuel I would think, because it will run for a while..and even idle as well.

I can hear the motor popping and misfiring at idle, and slightly faster than idle speeds. When the motor is at full throttle, its really only going around 1/2 to 3/4 throttle speed of how its supposed to run. So obviously one or more cylinders are not firing properly. But I checked out each cylinder, and it doesn't appear to be one specific cylinder causing the problems. Not sure where to go next. I been reading my manual all evening.

 

[tashasdaddy]

Re: slight misfire/ Ignition? Fuel?

do a compression check on all cylinders, for a base line. then a spark check, jump 1/2 -7/16 inch. remove and clean all electrical connection. you can take an induction timing light, with you and clip on each plug wire, and watch the light for failures in spark.

 

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Re: slight misfire/ Ignition? Fuel?

You say it ran fine before taking it apart. What all did you do during this cosmetic makeover? WHat did you have apart and how long did it sit out of operation?

 

[BigNiner19]

Re: slight misfire/ Ignition? Fuel?

You say it ran fine before taking it apart. What all did you do during this cosmetic makeover? WHat did you have apart and how long did it sit out of operation?

It sat about a month. I removed the outboard entirely from the boat. Im pretty sure everything went back on the boat the same as it came off. I even marked things that I could have mixed up so that I would remember where they went.

 

[Silvertip]

Re: slight misfire/ Ignition? Fuel?

If you removed the spark plug wires, are you sure you have them back on the correct plugs? The popping you describe is an indication of a timing issue. If you didn't mess with any of the linkage and the engine ran ok prior to whatever it is you did, then the plug wire placement is suspect. Are you sure you didn't swap the control cables which would account for the engine not reving fully. Bumping, bending, or breaking a timing advance linkage can cause the issue as well.

 

[BigNiner19]

Re: slight misfire/ Ignition? Fuel?

If you removed the spark plug wires, are you sure you have them back on the correct plugs? The popping you describe is an indication of a timing issue. If you didn't mess with any of the linkage and the engine ran ok prior to whatever it is you did, then the plug wire placement is suspect. Are you sure you didn't swap the control cables which would account for the engine not reving fully. Bumping, bending, or breaking a timing advance linkage can cause the issue as well.

The control cables seem to be installed just fine. They open the throttle just as they should and hooked up nicely to my new throttle control. The wires are on just as they were prior to removing the motor.

A timing issue would sound right...I will continue to try and figure out what to loook for with a timing problem that could have my motor not running right? Any suggestions on trouble shooting this?