Yanmar 6LPA-STP2 Constant Alarm – Suspect Dash Bulbs, But Open to Other Ideas

[Buddy28TE]

Hi all, I’m troubleshooting a persistent alarm issue on my 2002 Albin 28TE with a Yanmar 6LPA-STP2 diesel.

What’s happening:
• Initially, the alarm would chirp intermittently about 4–5 minutes after getting on plane, then stop.
• A mechanic came aboard to help diagnose the issue. He disconnected something in the alarm circuit, then reconnected it — and ever since, the alarm goes into a constant active state as soon as I turn the ignition on (even before engine start).
• I’ve noticed that only one of the seven indicator lights on the dash (oil pressure, coolant temp, turbo, etc.) lights up when I turn on the ignition. The others remain off.
• I’ve ordered BA7S 12V 2W bulbs to replace all the dash indicators, since I now suspect that multiple burned-out bulbs may be breaking the warning circuits and triggering the alarm.
• All engine gauges are reading within normal ranges (oil pressure, coolant temp, voltage, etc.), both before and after the alarm triggers.

Voltage behavior:
• After the boat has been unplugged from shore power and sits for 20–30 minutes with the engine off, voltage drops to under 10V before startup.
• After engine start, voltage climbs to 13.50–13.85V, but it never exceeds 14V.

Looking for input on:
• Could this be a wiring issue, dash logic fault, or alternator problem, in addition to or instead of bad bulbs?
• Is the sub-10V reading before startup a sign of a weak battery or parasitic drain?
• Has anyone else had a burned-out dash bulb cause a constant alarm or strange sensor behavior?

I still feel the bulbs are the most likely culprit, but would really appreciate any insight or similar experiences. Thanks!

–Shawn

[catalina_mike]

There is also a low coolant level alarm as I remember. Your alternator may not be reaching full voltage because of the load charging the battery. your battery is suspect if it drops voltage that fast. Verify with a voltmeter at the battery. Also try running on the house battery and see if the symptoms continue.