I've got a 2003 Yamaha 115 Jet with a Tiller
It's always ran good until recently. After sitting for a half season, it now won't run above idle without misfiring. Seems to only be running on two cylinders once it starts up and settles in. I've inspected/corrected all of the likely causes.
Disconnecting bottom plug wires when engine is running changes nothing. All cylinders are getting good compression, spark AND fuel. Seems like the timing is off when trying to rev engine.
Cleaned carbs.
Replaced all fuel lines and filters.
New plugs.
New Fuel Pump
New head, water jacket and thermostat gaskets.
New thermostats.
Compression 135 +/- on all cylinders.
When switching the key almost off, it will smooth out momentarily. I thought it might be a short in the key box so I disconnected the ignition after starting to isolate and no change in performance.
When hitting EITHER of the trim switchs (on the tiller or the engine) to the "down" direction, the engine runs normally while the switch is held in the down position.
I reversed the wires out of the trim solenoids to the trim motor and it has the same effect on the engine. Trim button down (engine up now) still smooths out the engine while the switch "down" is engaged.
Is there likely a short somewhere that would cause the engine to run correctly only when the trim button is engaged in one direction only, a problem with the trim solenoid, or the ECU?
Thanks in advance!
It's always ran good until recently. After sitting for a half season, it now won't run above idle without misfiring. Seems to only be running on two cylinders once it starts up and settles in. I've inspected/corrected all of the likely causes.
Disconnecting bottom plug wires when engine is running changes nothing. All cylinders are getting good compression, spark AND fuel. Seems like the timing is off when trying to rev engine.
Cleaned carbs.
Replaced all fuel lines and filters.
New plugs.
New Fuel Pump
New head, water jacket and thermostat gaskets.
New thermostats.
Compression 135 +/- on all cylinders.
When switching the key almost off, it will smooth out momentarily. I thought it might be a short in the key box so I disconnected the ignition after starting to isolate and no change in performance.
When hitting EITHER of the trim switchs (on the tiller or the engine) to the "down" direction, the engine runs normally while the switch is held in the down position.
I reversed the wires out of the trim solenoids to the trim motor and it has the same effect on the engine. Trim button down (engine up now) still smooths out the engine while the switch "down" is engaged.
Is there likely a short somewhere that would cause the engine to run correctly only when the trim button is engaged in one direction only, a problem with the trim solenoid, or the ECU?
Thanks in advance!
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