2000 merc 5.0l alpha one gen two

[thirstymate]

Engine sn 0L686854
Transom an 0L867686
Drive Sn 0L790665

Short version of the long back story;
Bough the boat (2000 Glastron Gx205) a week ago. Not running, as is... 68 hours.
I worked near 5 years as an Avionics tech, now while I'm not the best, I know my way around schematics and testing equipment. While looking at the boat, it was easy to discern from the wiring diagrams I was able to find that the parts that were being thrown at it to get it running were symptoms and not the cause. The bad ECU was the cause. Got an ECU and the boat runs.

The root of the problem that I can discern is the storage tactics for the last 2 years, which was a tarp... In Maine. The mildew on the seats was extensive and the havoc that was set to the electrical systems remains in question. Either the mercruiser systems have a 20 year shelf life, or do not under any circumstances store a boat under a tarp where the temperature and humidity fluctuate rapidly.
So, smoked the ECU which is now resolved.i found an mefi3 for a 5.0L of the same year. Got lucky. Utilizing the technique from the cars I had in the 90's pre obdII, and this website, I was able to pull a code 23 and code 34. Tested the IAT sensor, which was just wide open, aka dead, and without a clear way to test the MAP/MAT sensor I just ordered one as well. So for the extent of this post, those codes are resolved. This brings me to the last odd ball. The warning horn. Key on engine off, I get one beep followers by two short beeps. Then the beep sequence of one beep every (approx, I haven't timed it) 10 seconds starts. Running or not it continues. The only mention of anything remotely like this I can find is a description of an "intermittent beep" from a low drive oil level. This boat has the drive oil monitor system in it with the aux reservoir. I just want to make sure I'm not missing something, that this math adds up. Is anyone aware of a scenario that would cause this audio warning pattern? I do have a Seloc manual, but I am a bit at odds with it as it's useful information seems to be a bit misplaced ( ECU pinout in the fuel section? ) And more pertinent information like oil quantity and quality seems to be non existent. But it has helped none the less.

If nothing else, thanks for posting what you folks have in regards to other issues, it has helped a bit in deciphering this puzzle.

 

[thirstymate]

Wow. I just realized I've been utilizing these pages to fix my boats for 12 years and this is my first post. Well, thanks folks, that's quite a few boats.

 

[dubs283]

two beeps every ten seconds indicates a "non-severe" fault

is the gear lube monitor full?

sometimes the float gets stuck and will trigger the alarm, you can disconnect one of the two wires coming from it with the key off, then turn key to the "run" position to see if it goes away

otherwise there is another fault code that is active, best option to find it is to use a proper diagnostic tool/software

 

[alldodge]

get one beep followers by two short beeps. Then the beep sequence of one beep every (approx, I haven't timed it) 10 seconds starts.

The one beep is a soft alarm. Most alarms are constant or 2 beeps

There are a bunch for 2 beeps, but even a soft alarm should show a code
Check the 5V reference (like at the MAP) to see if its a bit off from 5V

 

[thirstymate]

So I timed the beeps this morning. Key on engine off it's 1 beep every 4 seconds.
I'm thinking I need to get the codes cleared from the ECU and start over since the ECU is not native to the boat and may have stored codes in it. I tried the 100% throttle in maintenance mode and that didn't seem to have an effect.

I did check the monitor, it's full. I disconnected both sides to it, but not just one... Not sure I understand there would be a difference. The monitor switch was open as was the oil level sensor. I can't find if those are open or closed to activate.
I'll replace the iat and map sensor when I return from my work trip on Friday.

 

[alldodge]

The lube bottle, is open (has lube) or closed (has no lube) and it just grounds one side.

Don't throw parts at it, get it scanned, or use the paper clip and LED to figure it out

 

[dubs283]

I did check the monitor, it's full. I disconnected both sides to it, but not just one... Not sure I understand there would be a difference. The monitor switch was open as was the oil level sensor. I can't find if those are open or closed to activate.
I'll replace the iat and map sensor when I return from my work trip on Friday.

as AD stated the lube monitor is normally open, as is the oil pressure switch and the temp switch. all three switches close when the threshold is breached and complete the warning horn circuit to ground, thus the horn sounds

seeing as how you haven't replaced the IAT which you noted does have a fault it is likely that (or something else) is the source of the alarm. until the ecm reads any sensor as normal it will continue to trigger the active fault alarm. unplugging the sensor in question will not alleviate the fault, the ecm will read the circuit as open or short to ground depending on the sensor and the fault will remain active

 

[thirstymate]

as AD stated the lube monitor is normally open, as is the oil pressure switch and the temp switch. all three switches close when the threshold is breached and complete the warning horn circuit to ground, thus the horn sounds

seeing as how you haven't replaced the IAT which you noted does have a fault it is likely that (or something else) is the source of the alarm. until the ecm reads any sensor as normal it will continue to trigger the active fault alarm. unplugging the sensor in question will not alleviate the fault, the ecm will read the circuit as open or short to ground depending on the sensor and the fault will remain active

Thank you. The parts will be here on Tuesday and I'll get them in. I had assumed as much. I figure if I still have the alert after replacing the sensors that have caused codes, then I will have to get it scanned to see what may be causing it. I'll report back.

Also, alldodge, I'm not throwing parts at it. I believe I mentioned above that indeed I did read the ecm codes, and those codes provided me with sensor faults. Those are the sensors I'm replacing. Maybe you have this post confused with another.

 

[thirstymate]

Update:
The codes I pulled from the ECU were good. And apparently the only issues. With just the ignition on I get two brief beeps and nothing else after that. Running on not. Which I can only assume is exactly what it should be doing.
One thing to add, instead of getting an LED etc, I simply rigging my volt meter (set to audible continuity) and counted the beeps. Worked great.
Thanks gents, I appreciate the responses and the time. This forum has helped on multiple occasions over the years. I'm sure I'll be back at some point but hopefully after the summer and not for odd beep patterns. Enjoy the summer.