SabrToothSqrl

I have twin Merc 350s, and using the LED / switch trick (same as the CodeMate).
I was able to identify and correct 2 Diagnostic Trouble Codes on the same engine.
DTCs that had I not looked for, I'd have never found. Because... there is no check engine light...

Which, got me thinking.
Why not just wire in the LED permanently? (not the switch, that's just for troubleshooting).
Would there be any harm in wiring in the 12v LED to the engine and just leaving it there?

I usually start my engines with the hatch open, so a lit LED after start would quickly indicate an engine issue.
(Light goes off if everything is normal).

I've read that some boat makers wire this to a light in the dash.
I'm not going to take the time/hassle, but figure this is the same thing really...
I'd just zip tie or attach the LED to the engine somewhere visible.

Good idea? Bad idea?
S/N: 0M047350

thanks

BUP

2008 California and 2010 the rest of the USA --- most marine engines under 500 hp have check engines lites (MIL) at the dash --- for the CAT engines. Before the CAT engines and even currently --- Some boats for many years have an over heat warning lite at the dash. Some even have low voltage warning lites that connect in with certain battery switches. Some of the faults will never be picked up with a lite as you found out with the winky blinky plus what I said.

for the past 18 years Merc smartcraft displays faults on its smartcraft gauge but all that started and is linked into PCM and ECM 555, and PCM 09 and 012 controllers. .

SabrToothSqrl

I'm going to wire it up, make it all nice and water proof.
I only have 1 LED so far, so I'll order another to get matching before I install.
Then I'll have check engine lights on my 2001 boat engines.
It won't catch everything, but otherwise you could have a DTC for years and not know...

https://www.ebay.com/itm/6mm-6-12V-C...19.m1438.l2649

I'll wire these in behind the connector, with waterproof heatshrink connections.
Mount the LED to the side of one of the brackets or similar.
I'll be able to see them from the cockpit if the hatch is up.
Lights go on at run, then turn off once the engine is started if everything is normal.
Light remains on = issue and test for DTCs.

Someday I'll have that fancy stuff.
Checked out a SEA-RAY L650 over the weekend at a boat show... really, really liked it.