1993 Johnson 30hp misses at WOT

[rosentreter]

Hello, trying to narrow this down. At WOT my 1993 Johnson 30hp experiences an intermittent miss lasting a half second or so. Back off the throttle just a little and no miss. The miss might happen every 2 to 5 seconds. It is like somebody cut the power, no stumbling or trouble maintaining rpm. Motor behaves well in all respects.

Thinking stator related, if it were a coil pak it would not be a complete miss just a stumble.

Thanks for any feedback. Rich

 

[oldboat1]

Drop cylinder test at high rpm to see which one is missing.

 

[racerone]

Test run with the cowling off.--------Test run with a timing light to see if it is one or both cylinders that have the miss.

 

[flyingscott]

Check the wires coming out of the stator may have one that rubbed bare and is hitting.

 

[rosentreter]

I am pretty sure it is both cylinders because just one dropping out would cause a stumble and not a complete dead miss. I have seen motors with a missing cylinder run and not miss like mine. it goes rrrrrrrrrrrrrrr miss rrrrrrrrrrr. I will check the stator wires first. That would be a nice easy fix wouldn't it Thanks for the help guys.

 

[racerone]

I am not there to observe.----You are sure it is not jumping out of gear ??

 

[rosentreter]

100 % positive

 

[oldboat1]

Might be helpful to post a clip of it running and acting up.

 

[scatgo]

How did things work out?

 

[rosentreter]

I couldn't find any bad wires from the stator but I did not take the flywheel off either yet. I still think it is a short. Will take it out Saturday to salmon fish the Columbia and post a clip of what it does at WOT. Thanks.

 

[oldboat1]

Wow. In the river or out and over the bar? You might check your fuel tank for water before going out -- pull some fuel from the bottom of the tank and let it settle out overnight in a glass jar. See if it separates (water would be on the bottom).

 

[tblshur]

does it happen out of the hole on take off or just on plane? my boat has a black yellow striped wire from key switch to power packs yours may be different ignition see if motor stills misses caution have another means to kill motor choke or run another wire hope this helps:joyous:

 

[rosentreter]

It happens on plane.

My motor has a stator right? Is it called a charge coil in the parts diagram?

 

[oldboat1]

#45 in the diagram: http://ww2.iboats.com/Ignition/dm/cart_id.036319395--session_id.523588008--view_id.1548171

 

[racerone]

I think #45 is strictly for charging the battery.----#35 is charge coil for ignition system and #30 is sensor coil for the ignition system.

 

[oldboat1]

Both the stator and charge coil produce A/C current, converted to D/C by the rectifier and the ignition module (power pack). The power pack stores D/C in a capacitor. The sensor coil contributes to selection of the correct ignition coil by electronic switches in the pack -- which directs capacitor output to the selected ignition coil.

(Personally, I think there are little ghosts in there that make the system work, but that doesn't show up in the manual.)