Engine hours

[jdreher]

I have a 2002 Tige 21i TypeR with a MerCruiser 350 MAG MPI. I use a trickle charger all winter on it, with the battery connected to the boat. I read on another forum that this will add hours to the engine even with the key off. Does anyone know if this is true?

[boatwakes]

Negative, the engine computer does not register hours unless the engine is running. However, if you have an analog hour meter, leaving the key on will add hours.

[jdreher]

That is what I thought. The reason I asked is my hour gauge is digital and some of the LED's are out, I thought. I took it to a Mercruiser Repair shop and they hooked it up to their EMC and my boat has 1315 hours on it, according to their EMC. Last night I had just finished doing a 24 hour charge on the battery and turned my key to check my battery amperage and my hours meter was working perfectly fine, reading 784 hours. So why is there a difference in hours. I have used a trickle charger every day, for the 8 months it sits in the garage waiting for nice weather, for the past 14 years. Could the EMC be adding trickle hour usage to the hour meter gauge???

[lee]

ECM is correct, hour meter is wrong.

[boatwakes]

The engine control module logs its hours independent of the analog gauge and often times, especially with older gauges, the analog will crap out and need to be replaced. A prudent replacement would have the previous hours written on the back of the new gauge but again, the engine computer stores actual hours.

[jdreher]

I have read people buy new hour meters and wire it straight to a battery to have the new hour meter roll forward to what the old meter said before they install it. With that, if the current battery does not have a direct shut off, if my key is turned could that cause the EMC hours to be different from the hour meter?

[boatwakes]

Ok, lemme splain...
Hour meter dash gauge will operate and accumulate hours when ANY 12volt source is applied to it (key on, directly wired to the battery etc...), literally a useless item on the dashboard and never displays correct engine hours.

The engine control module, also called the ECM, only accumulates hours when the engine is running, even if the key is in the on position. The ECM does not accumulate hours if the key is on and the engine is NOT running. It requires an engine diagnostics computer to read but is ALWAYS the CORRECT engine run time hours logged on that particular computer.