Hi all. Working on a ~1985 Mercury Black Max 175 that was in storage for 12 years. I’m told by the owner that it was completely overhauled shortly before going into storage, and he wants to keep everything as is as much as possible. I know deleting the oil injection and running premix is popular, but that’s not what he wants to do since everything was replaced, so please don’t just suggest that.
With that out of the way, I have the motor running fine except getting an oil alarm (beep beep beep, not constant tone) over 3000 RPM or so. Things we've done/tried/tested since pulling out of storage:
Engine starts and runs fine at all RPMs. It smokes a bit, smells like a 2 stroke, etc. It is getting oil. Below 3k RPM, it'll run all day with no alarm. Alarm starts quickly over 3k RPM. Once the alarm starts, it will not stop until the motor is shut off. The alarm will not sound when the oil pump rotation sensor is unplugged. But it is rotating and pumping oil at the rate it's supposed to and giving the proper 5V pulse. The magnet is encased in the coupler between the pump and drive shaft, there’s no way for it to fall out or be in backwards.
I have a DVA on the way to check the stator output since the warning module compares signal from that to the rotation sensor to make sure the pump is rotating with the engine. Was thinking maybe the high speed coils are not quite up to spec. Doing a simple impedance check, the stator is not within spec.
Any ideas what could be causing this? Am I on the right track with the stator potentially? Or what about a switchbox? Again, I want to find the actual answer here, not just delete and premix per owner's desire.
Thanks!
With that out of the way, I have the motor running fine except getting an oil alarm (beep beep beep, not constant tone) over 3000 RPM or so. Things we've done/tried/tested since pulling out of storage:
- Compression checks good, bore scoped cylinders
- New fuel lines and rebuilt fuel pump
- New plugs, coils, and spark plug wires
- New impeller/water pump and thermostat
- Oil reservoir cap checks good
- Oil pump flow rate checks good per service manual
- Checked oil pump drive gear and driven gear on crank with borescope
- Oil pump rotation sensor and oil cap checks good
- New warning module
- Swapped green wire from warning module to multiple cylinders
- Trigger impedance checks good
- Stator impedance is not within spec
Engine starts and runs fine at all RPMs. It smokes a bit, smells like a 2 stroke, etc. It is getting oil. Below 3k RPM, it'll run all day with no alarm. Alarm starts quickly over 3k RPM. Once the alarm starts, it will not stop until the motor is shut off. The alarm will not sound when the oil pump rotation sensor is unplugged. But it is rotating and pumping oil at the rate it's supposed to and giving the proper 5V pulse. The magnet is encased in the coupler between the pump and drive shaft, there’s no way for it to fall out or be in backwards.
I have a DVA on the way to check the stator output since the warning module compares signal from that to the rotation sensor to make sure the pump is rotating with the engine. Was thinking maybe the high speed coils are not quite up to spec. Doing a simple impedance check, the stator is not within spec.
Any ideas what could be causing this? Am I on the right track with the stator potentially? Or what about a switchbox? Again, I want to find the actual answer here, not just delete and premix per owner's desire.
Thanks!