Hi all, after a year of trouble-free use, last week I encountered a problem with the 1994 Mercury 3.0L Offshore 225hp 2-stroke (carbureted) on my boat. Twenty minutes into a trip, an alarm came on which I assumed was low oil (light flashing and beep once every 2 seconds). We didn't resolve it out on the water, so I got a tow back to my slip. The next morning, the alarm persisted and I also found I couldn't get the engine started. Today, a few days later, I managed to start the engine, but it seems to be idling rough. The alarm, though, is still continuing.
Other key points:
-- The alarm comes on 15 seconds after either (a) starting the engine, or (b) just turning the key to "on" without starting the engine.
-- It's a beep and flashing light once every 2 seconds, and just keeps going indefinitely. By comparison, the shop manual for my engine says there are two kinds of alarms: (a) overheating (light and sound continuously), or (b) low oil/fuel-water separator fault, which is supposed to be a flash and beep once per second. The manual says this repeats four times, and then takes a break for two minutes. My alarm doesn't take a break -- it's a flash and beep once every *two* seconds, continuing indefinitely until I turn the key off.
-- The 2-stroke oil system appears to be in order. The remote tank under the console is full and is sealed properly. The oil reservoir in the engine is full. I've tested the sensor on the reservoir, and it responds correctly (it shows an open circuit -- i.e. infinite impedance). I've also tried temporarily disconnecting this sensor, but this doesn't stop the alarm. Although I understand some engines also have a motion sensor on the oil pump's drive shaft, my engine doesn't appear to have this. (Plus, as noted, the alarm comes on if the key is just turned to "on" without starting the engine.)
-- The fuel-water separator system also appears normal. My spin-on fuel filter is mounted outside of the outboard underneath the aft end of the starboard gunnel. There is no sensor on this filter. Just to rule out an issue with water in the fuel, I changed out the spin-on filter today and drained the carbs. The fluid that I poured out of the old filter didn't have any obvious separated-out water in it. The gas in our area doesn't contain ethanol.
-- I also generally checked the wiring in the engine, snugging up connectors and checking continuity at ground connections, etc. I noticed that there are two wires (one is tan-colored with a light line, the other is light-colored with a black or dark line) coming out of the harness from the electronic control module (ECM) that are disconnected and just laying on the bottom of the engine housing. I'm wondering if these would normally go to a fuel filter sensor? However, there are insulators on the ends of each of them that would prevent them from shorting out (like the oil reservoir sensor, the fuel filter sensor signals a fault when it is grounded out).
I'm not sure what to try next. If I had an extra ECM and/or alarm module I might try swapping these out, but they are expensive (and, in the case of the ECM, the local Merc dealer says it is no longer available). Any suggestions would be great.
Other key points:
-- The alarm comes on 15 seconds after either (a) starting the engine, or (b) just turning the key to "on" without starting the engine.
-- It's a beep and flashing light once every 2 seconds, and just keeps going indefinitely. By comparison, the shop manual for my engine says there are two kinds of alarms: (a) overheating (light and sound continuously), or (b) low oil/fuel-water separator fault, which is supposed to be a flash and beep once per second. The manual says this repeats four times, and then takes a break for two minutes. My alarm doesn't take a break -- it's a flash and beep once every *two* seconds, continuing indefinitely until I turn the key off.
-- The 2-stroke oil system appears to be in order. The remote tank under the console is full and is sealed properly. The oil reservoir in the engine is full. I've tested the sensor on the reservoir, and it responds correctly (it shows an open circuit -- i.e. infinite impedance). I've also tried temporarily disconnecting this sensor, but this doesn't stop the alarm. Although I understand some engines also have a motion sensor on the oil pump's drive shaft, my engine doesn't appear to have this. (Plus, as noted, the alarm comes on if the key is just turned to "on" without starting the engine.)
-- The fuel-water separator system also appears normal. My spin-on fuel filter is mounted outside of the outboard underneath the aft end of the starboard gunnel. There is no sensor on this filter. Just to rule out an issue with water in the fuel, I changed out the spin-on filter today and drained the carbs. The fluid that I poured out of the old filter didn't have any obvious separated-out water in it. The gas in our area doesn't contain ethanol.
-- I also generally checked the wiring in the engine, snugging up connectors and checking continuity at ground connections, etc. I noticed that there are two wires (one is tan-colored with a light line, the other is light-colored with a black or dark line) coming out of the harness from the electronic control module (ECM) that are disconnected and just laying on the bottom of the engine housing. I'm wondering if these would normally go to a fuel filter sensor? However, there are insulators on the ends of each of them that would prevent them from shorting out (like the oil reservoir sensor, the fuel filter sensor signals a fault when it is grounded out).
I'm not sure what to try next. If I had an extra ECM and/or alarm module I might try swapping these out, but they are expensive (and, in the case of the ECM, the local Merc dealer says it is no longer available). Any suggestions would be great.