Mercruiser 5.0L - Constant alarm at start

[Kneitzey]

Hi All,

I want to start by saying i've looked up and down this form (and others) at previous posts regarding the MerCruiser alarm system. This forum has provided me with a TON of valuable info in the past.

Specs
Boat: 2005 Bayliner 219 SD
Engine: 5.0L MerCruiser Carb
Engine Serial: 0W044469
Outdrive: Alpha 1 Gen 2


Summary of issue
It all started as random beeps of the alarm, typically when getting up to speed. Alarm would sound, few beeps then constant for 30sec-few minutes, then off for a few minutes. (no pattern) Backing down on throttle slightly would sometimes cause it to turn off but sometimes would also sound at low RPM. All gauges seem to be normal. Temp normal. Oil Pressure normal. Gear lube full.

- Impeller / water pump was replaced this summer
- Thermostat replaced
- Both temp sensors replaced that were located on thermostat housing
- Gear lube & sensor replaced
* The only sensor i have not yet replaced is the oil pressure sensor.

Today after reading multiple posts, I tried, as suggested, disconnecting each sensor one at a time until the alarm went off.

The constant alarm never turned off.

I thought for sure that the Oil pressure sensor was the culprit, however i'm baffled as to why the alarm remains constant when all sensors are disconnected. Could this be a bad ground? Bad alarm?

To clarify, the alarm initiates when the key is turned to "on" and remains constant even while running all the way to temp.

There are no signs of overheating, motor runs strong.

Hoping someone on here can point me in the right direction on what / how to troubleshoot next. I plan on replacing the Oil Pressure sensor next, but its a tight squeeze and figured I would troubleshoot first before replacing that one. Thought for sure disconnecting all sensors would point to the oil pressure sensor.

Thank you!

 

[achris]

Alarm tones can be also generated by the TB-V ignition module. If you have all the sensors disconnected and you still have the alarm, I would start looking for a shorted wire. The wire from the engine to the alarm module is Tan/Lt blue in colour. Look along the wire all the way from the engine, and including the engine harness, to the instrument panel to the small alarm siren itself. It could be abraded through and shorting out, causing the alarm to sound....

If that wields no result, then swapping the ignition module may be the solution.

Chris........

 

[badrano]

I found a PDF from section 4D of some manual that has the wiring diagrams for all the different merc engines. It shows the tan/lt blue wire from ICM with a note saying that the wire is not used and basically is cut and tapped off.

I just bought a boat with the 5.0L TKS and I put a post out about the alarm not working when the key is ON but engine not running. I read the posts about how to trouble shoot the alarm issue.

Looking at the diagram, maybe you have that tapped off wire somewhere touching ground.

 

[NicosNicolaou]

Hi All,

I want to start by saying i've looked up and down this form (and others) at previous posts regarding the MerCruiser alarm system. This forum has provided me with a TON of valuable info in the past.

Specs
Boat: 2005 Bayliner 219 SD
Engine: 5.0L MerCruiser Carb
Engine Serial: 0W044469
Outdrive: Alpha 1 Gen 2


Summary of issue
It all started as random beeps of the alarm, typically when getting up to speed. Alarm would sound, few beeps then constant for 30sec-few minutes, then off for a few minutes. (no pattern) Backing down on throttle slightly would sometimes cause it to turn off but sometimes would also sound at low RPM. All gauges seem to be normal. Temp normal. Oil Pressure normal. Gear lube full.

- Impeller / water pump was replaced this summer
- Thermostat replaced
- Both temp sensors replaced that were located on thermostat housing
- Gear lube & sensor replaced
* The only sensor i have not yet replaced is the oil pressure sensor.

Today after reading multiple posts, I tried, as suggested, disconnecting each sensor one at a time until the alarm went off.

The constant alarm never turned off.

I thought for sure that the Oil pressure sensor was the culprit, however i'm baffled as to why the alarm remains constant when all sensors are disconnected. Could this be a bad ground? Bad alarm?

To clarify, the alarm initiates when the key is turned to "on" and remains constant even while running all the way to temp.

There are no signs of overheating, motor runs strong.

Hoping someone on here can point me in the right direction on what / how to troubleshoot next. I plan on replacing the Oil Pressure sensor next, but its a tight squeeze and figured I would troubleshoot first before replacing that one. Thought for sure disconnecting all sensors would point to the oil pressure sensor.

Thank you!

Did you spot what was causing the issue?

 

[GA_Boater]

Did you spot what was causing the issue?

Two years ago the OP did a drive by, shot one post and skittered away. He's on wanted posters in the Post Office, but still in hiding,

Closed.