Continuous alarm and 30 second shutdown (plus)

[dgyank70]

Hello all.
First my engine info:
Engine Info (transom ID)
August 2008, serial #A177296
Mercruiser v6 4.3l with TKS (tks is disabled / bypassed due to prior issues)

Short story:
This morning I had a continuous buzzer on startup.
Stopped and doublechecked my gear oil reservoir sensor was still disconnected (leak hasn't been fixed)- it was.
Noticed what seems to be fresh engine oil (dark) in the bilge, so I checked the engine oil.
That seemed low to me, dipstick was looking dry.
I ran it just a few hundred yards, at slowest rpm, 30 seconds at a time, to my neighbor's dock.
Added 1-2.5 quarts or so (came out of a larger jug I happened to have).
Still had buzzer continuous, boat actually stops after about 30 seconds, repeatedly, as though a protective shutdown. (Coincidentally, also seems to make me prime the throttle to restart it- is that how it shuts down, kills the fuel, making that necessary?).

Questions / hypotheses / troubleshooting guesses:

1. Is it possible I still didn't add enough marine oil to make the buzzer stop?
2. Is it possible the 'error' needs to be reset (i.e., maybe disconnect the battery, like when a car sometimes has an error code 'stuck' in its memory even when the problem is fixed)?
3. Is there anything besides temp, marine oil, or lube oil that would make a continuous buzzer and/or shut the engine down?

-my gauges have largely been inoperable for a while (either sending unit or gauge or both are bad)
-however, it's 100% clear that there was not a (true) high temp problem (started immediately, with cold engine, at low rpm, in cool lake water- engine not warm)
-the oil in the bilge is suspicious- haven't had an (engine) oil problem historically; but perhaps it finally leaked out enough, or perhaps the last marine shop didn't quite properly put the oil filter / oilpan cap on cleanly, and it's shaken loose just enough?

Next steps:
I need to get my gauges functional again anyway, so my next steps would seem to be to dig into the sending units / sensors and/or the gauges themselves, to see if they help clarify what's happening (like a bad temp sensor).
(Please see my future post on gauges to help me figure out how to get those back online, as it might help answer things if they were working (like if the temp were falsely being reported as hot by a bad sending unit, or the same with the oil, etc).)
Is there anything else? Should I bother with trying to disconnect the battery for a bit?
I'm basically looking for feedback on diagnostics / further info about when / why the engine would shut down, if I'm missing anything on that front. As an example, I'm sure I could also just have an ECM / ECU problem suddenly appear, but that doesn't seem likely.

I recently put my boat back in the water after being in the shop last season (mostly for gauges not working, and for a gear oil leak).

Longer Story
~4 weeks in the water, ~15 hours running.
First trip from the marina:
Below 2k rpm, things ok.
Around 2k rpm, buzzer would go off intermittently (not solid), and engine would stumble, fall down.
Note the orangeish wire- there were also a couple black looking ones that seem like the marine shop didn't reconnect. Our thought is perhaps the orange was grounding out / sending a bad signal, causing the buzzer and stumbling...
After ensuring it wasn't bumping against the engine, the motor ran just fine for probably 6-10 hours over the span of a couple weeks, no issues.
So we don't know exactly what was happening at that time, but it seemed like perhaps that was a sensor tripping the alarm buzzer and also somehow affecting the engine operation.


Ran the boat sporadically for the past couple weeks, and then this week, ran the boat a good 6-10 hours over three days, including last night for a couple hours.
Dragged tube riders, etc. The most exercise it's gotten for quite a while.

This morning, I went to take it to the marina, and found the buzzer running continuously after starting.
I checked the historical issue of gear oil reservoir sensor-still unplugged, the marine shop never did fix that leak, so I've disconnected the sensor for quite a while now.

As far as I know, the reasons for buzzer are
-temperature
-oil pressure (or level)
-gear oil reservoir
So I think I'm down to 2.
The gauges have been inoperable for quite a while (not sure if it's the gauges or sending units- will have another post on that in a second), so neither oil nor temp are telling me anything.
That said, it seems impossible that I have a true temp problem- the engine was cold and barely ran, and there was no heat when I opened the engine compartment...
It's possible I have / had a real oil pressure or level problem, as I 'believe' the oil in the bilge is a new issue. However, having added a quart or two, and the dipstick now reading properly, I would think the buzzer would have stopped.

 

[alldodge]

The over Temp switch is on the thermostat housing. This switch will have 2 wires and unplug it to see if buzzer stops. Most the alarm signals go thru the TB-V ignition module.

The orange wire came from the TKS Temp switch that is no longer used

 

[dgyank70]

Thank you very much!!!
Just to be clear- you mean because I disabled the TKS, correct?

 

[alldodge]

Thank you very much!!!
Just to be clear- you mean because I disabled the TKS, correct?

Not really but to clarify
Your correct that oil pressure, water temp and drive lube will sound the alarm

The TKS module also had a Temp switch but was not part of the alarm, it just kept power to the TKS module once it warmed up. TKS has been disabled so the disconnected orange wire is not an issue

I did not see where you disconnected the water temp switch so it may be that is what's keeping alarm ON, unplug it and see.

If alarm still sounds then it could be part of the TB-V ignition system or a chafed wire for one of the switches mentioned previously above

 

[dgyank70]

In the time I posted, my neighbor found what he thinks are 2 engine oil (as opposed to gear lube, which we have disconnected) sending units...
One is a 1 wire near the distributor, the other is a 2 wire near the oil filter.
I believe it's the 1 wire which when disconnected, ends the buzzer...

So it seems that there may be 2 oil sensors- I had thought only one...
Any thoughts on that?
Thanks!

 

[dubs283]

One next to distributor is the oil pressure switch for the audio warning system. The two wire switch near the oil filter connection is to power the electric fuel pump

 

[dgyank70]

One next to distributor is the oil pressure switch for the audio warning system. The two wire switch near the oil filter connection is to power the electric fuel pump

Gotcha- that is to perhaps kill the fuel to shut the engine down then?
And I just realized I posted the wrong serial # for my engine.
It's actually
1A335597

 

[alldodge]

Gotcha- that is to perhaps kill the fuel to shut the engine down then?
And I just realized I posted the wrong serial # for my engine.
It's actually
1A335597

Thanks for updated SN, good thing it's still in same model area

The warning horn switch under the Dizzy has nothing to do with the fuel pump, it only sounds the alarm

The one down by the remote filter connect does active the FP and has nothing to do with the alarm

 

[dubs283]

that is to perhaps kill the fuel to shut the engine down

Not exactly. The engine ceases operation by disconnecting the primary side of the ignition circuit via the key switch

The electric fuel pump is first powered through the starting system with voltage applied to the pump (+) lead from the starter solenoid. Once the engine is running and the key switch disengaged from the start position the oil pressure switch (pump not audio warning) circuit allows voltage to be continuously supplied as long as oil pressure is present and the switch/associated circuitry is sound.

If oil pressure is not present and all sensor/switches and associated circuitry is sound the engine will not run for long and an audio warning horn will sound. With little/zero oil pressure the fuel pump/oil pressure switch will open and not allow voltage to operate the pump to pass through. Not to mention the engine mechanical damage that would occur from such low oil pressure

 

[dgyank70]

Not exactly. The engine ceases operation by disconnecting the primary side of the ignition circuit via the key switch

The electric fuel pump is first powered through the starting system with voltage applied to the pump (+) lead from the starter solenoid. Once the engine is running and the key switch disengaged from the start position the oil pressure switch (pump not audio warning) circuit allows voltage to be continuously supplied as long as oil pressure is present and the switch/associated circuitry is sound.

If oil pressure is not present and all sensor/switches and associated circuitry is sound the engine will not run for long and an audio warning horn will sound. With little/zero oil pressure the fuel pump/oil pressure switch will open and not allow voltage to operate the pump to pass through. Not to mention the engine mechanical damage that would occur from such low oil pressure

Thanks guys!
As an update, my neighbor put a manual pressure gauge onto the engine and got readings I think in the 30-60 range, which he thinks means the sensor may be bad...
I don't know the normal pressure or whether it changes under load, but he was pretty confident it meant I wasn't truly lacking oil or pressure thereof...

Thanks again for the help!!

 

[alldodge]

Your oil pressure is good

 

[dgyank70]

Sweet! So it is likely the sender giving a bad signal. On the hunt to find a replacement. Thanks again!

 

[dgyank70]

Sweet! So it is likely the sender giving a bad signal. On the hunt to find a replacement. Thanks again!

Hello all, just sharing a final recap, thanks for all the help.

Buzzer wouldn't turn off, engine would cut off after 30 seconds.
Seemed to see oil in the bilge, and dipstick was low (with no prior oil issues).
Added some oil to get to normal on dipstick.
Still exhibited the same behavior.
Disconnecting the wire from the oil pressure sensor stopped the alarm.
Removed the sensor, replaced with a manual pressure gauge- this showed oil pressure ~30-60.
Ordered a replacement sensor; in the meantime, took the old sensor to a local marina and they had a (used) replacement for it.
The marina said the original sensor tested ok (i.e., responded to pressure).
Put in the 'new' (used) sensor, connected alarm wire.
Boat back to normal, buzzer stops, engine doesn't, proper rpms and such.

Hypothesis to explain it all:
-like in my car coincidentally, the pressure switch itself became a source of oil leak
-it was aware of its own leak, and therefore did not interrupt the alarm circuit, so it would continue buzzing.
-the other oil sensor connected to the fuel filter was likely seeing the pressure issue and cut off the fuel, killing the engine.
-It seems likely that the heavy use of the boat on Wed pushed the oil out the sensor to the point that by Fri morning, it showed low oil at start / on cold startup.


Sound about right?

My go-forward is to now see if there is still a leak (i.e., was the oil sensor itself the true source of the leak or not?), but I feel confident that both sensors were doing their job (i.e., keeping the alarm on and killing the engine).

Thanks again all!

Going to work on replacing all the gauges and getting all of the reading correctly to help with this all going forward...