I'm helping a buddy on his first boat. He purchased a super clean 1994 Champion 187 from a gentleman who swore it ran great. The engine is a 1994 Yamaha Pro V 150. It does run great, but we are getting a low oil warning light on the dash anytime we try to get on plane. This boat is equipped with the Yamaha digital tach. When the problem occurs, the green circle, the yellow oil can, and the red circle all start flashing, the warning chime turns on and the engine goes into reduced power mode. Once back at idle, all resets and its normal. Rinse and repeat. We've also starting getting an intermittent chirp from the chime at idle that sounds like morse code. I've done quite a bit of testing, so bare with me, but I'll explain all what I know.
Both oil tanks are completely full when this happens. I've ohm tested both the remote tank and main tank sensors. They both ohm perfectly fine in each position and the system operates as designed. Oil pump turns off when the blue/white wire is grounded, oil pump turns on when the blue/green wire is ground and the warning lights come on along with the chime when the blue/red wire is grounded. We even tried two known good sensors. Still the same issue. When the oil pump is commanded to come on, it pumps oil into the reservoir at a good rate. Again, the oil reservoir never goes low and the automatic oil system is working as designed. I can even disconnect both sensors and the warning chime still comes on under the same conditions. The gauge doesn't flash, but that's only because the sensors are unplugged. I know the engine is not overheating. We installed a new water pump, thermostat and poppet valve. I also brought my infrared heat gun out and it's within temp. Plus, the overheat light is the only one not coming on the dash. I checked the temp sensors, just to verify operation, by connecting both wires together and the circuit works. The overheat light comes on the tach and the alarm chimes. I've back probed the main oil sensor and wiggle wires and I cannot recreate the problem in the driveway or at idle. It ONLY happens when under acceleration. Sometimes at 3000 rpms, sometimes 4500 rpm, sometimes 2000 rpm. Very random, which is why it's been so hard to diagnose. I thought that maybe the float on the main reservoir was getting stuck under acceleration, so I zip tied it into the full position and tried again. Same thing happened.
I have even grounded out the green/red wire going to the tachometer and that will cause all three of the same warning lights to flash on the gauge, but it does not turn the warning chime on. The only time I can recreate the issue in the driveway while testing is if the CDI box thinks the main oil reservoir is low. I can do this by either just pulling out the sensor and manually lowering the float to empty, or if I supply ground directly onto the blue/red wire going into the CDI box. I know that these engines have a tilt/trim sensor that plays into the circuit but I believe it's only function is to turn the pump off if the motor is trimmed up too high. I don't think it has any way of turning the warning lights on? I mean, of course, unless it was not allowing the remote pump to come on, but that isn't the case with ours. I know the manual pump override switch is part of that circuit as well, but I don't believe it would have any way to cause a false alarm either?
Is this just a bad CDI box that doesn't like the vibration of the engine?? Or am I missing something? Maybe the stator or rectifier overcharging? If so, I would think more than just the low oil system would be malfunctioning. I could believe it was a chaffed wire, if I was only getting a short on the wiring harness to the gauge. But for the gauge to flash, and the warning chime to come on, I would have to have a short to ground on both the two pin (green, green/red) harness and the main 10 pin harness that has the pink warning chime signal wire in it. Possible, yes, but very unlikely. Wiggling wires hasn't worked so far. I'm lost!!
Both oil tanks are completely full when this happens. I've ohm tested both the remote tank and main tank sensors. They both ohm perfectly fine in each position and the system operates as designed. Oil pump turns off when the blue/white wire is grounded, oil pump turns on when the blue/green wire is ground and the warning lights come on along with the chime when the blue/red wire is grounded. We even tried two known good sensors. Still the same issue. When the oil pump is commanded to come on, it pumps oil into the reservoir at a good rate. Again, the oil reservoir never goes low and the automatic oil system is working as designed. I can even disconnect both sensors and the warning chime still comes on under the same conditions. The gauge doesn't flash, but that's only because the sensors are unplugged. I know the engine is not overheating. We installed a new water pump, thermostat and poppet valve. I also brought my infrared heat gun out and it's within temp. Plus, the overheat light is the only one not coming on the dash. I checked the temp sensors, just to verify operation, by connecting both wires together and the circuit works. The overheat light comes on the tach and the alarm chimes. I've back probed the main oil sensor and wiggle wires and I cannot recreate the problem in the driveway or at idle. It ONLY happens when under acceleration. Sometimes at 3000 rpms, sometimes 4500 rpm, sometimes 2000 rpm. Very random, which is why it's been so hard to diagnose. I thought that maybe the float on the main reservoir was getting stuck under acceleration, so I zip tied it into the full position and tried again. Same thing happened.
I have even grounded out the green/red wire going to the tachometer and that will cause all three of the same warning lights to flash on the gauge, but it does not turn the warning chime on. The only time I can recreate the issue in the driveway while testing is if the CDI box thinks the main oil reservoir is low. I can do this by either just pulling out the sensor and manually lowering the float to empty, or if I supply ground directly onto the blue/red wire going into the CDI box. I know that these engines have a tilt/trim sensor that plays into the circuit but I believe it's only function is to turn the pump off if the motor is trimmed up too high. I don't think it has any way of turning the warning lights on? I mean, of course, unless it was not allowing the remote pump to come on, but that isn't the case with ours. I know the manual pump override switch is part of that circuit as well, but I don't believe it would have any way to cause a false alarm either?
Is this just a bad CDI box that doesn't like the vibration of the engine?? Or am I missing something? Maybe the stator or rectifier overcharging? If so, I would think more than just the low oil system would be malfunctioning. I could believe it was a chaffed wire, if I was only getting a short on the wiring harness to the gauge. But for the gauge to flash, and the warning chime to come on, I would have to have a short to ground on both the two pin (green, green/red) harness and the main 10 pin harness that has the pink warning chime signal wire in it. Possible, yes, but very unlikely. Wiggling wires hasn't worked so far. I'm lost!!
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