ECM Question

[gerrpicc]

1997 7.4 MPIs
Had engines scanned recently to retrieve total hours for each engine. The hour meters show around 1300 but the scan shows around 240 for each engine. Could removing all batteries during winter layup to replace with new in the spring have caused the ECMs to be erased?
Thanks

 

[scoflaw]

No

 

[gerrpicc]

No

Thank you for the reply.
So next question is can the total hours even be reset?

 

[Thornton69]

Do your hour meters count with key on and engines off?

 

[gerrpicc]

Do your hour meters count with key on and engines off?

Not sure. I'll have to check but even if they do that wouldn't account for over a thousand hours difference.

 

[scoflaw]

Your hour meter will run with key on, mine is several hundred hours off in a 21 year old boat.
Maybe your ecm got replaced along the way. Your 24 year old boat only has a couple hundred hours?

 

[gerrpicc]

Your hour meter will run with key on, mine is several hundred hours off in a 21 year old boat.
Maybe your ecm got replaced along the way. Your 24 year old boat only has a couple hundred hours?

Hour meters show just over 1300 with a difference of about 5 hours from P to S
ECMs show 257 and 239.
I can see there being a difference due to key left on but over a thousand hours?
Can't think of a reason why the ECMs would both be replaced and motors are sequential and original by serial # and are period correct.

 

[gerrpicc]

OK, spoke with Mercruiser Customer support tech who advises that the ECMs only count total hours up to 999 and then start at 0 again. This would explain the roughly 1,000 hrs difference between hours on the ECMs and hour on the tachs/meters. That's a shocker and the yard that scanned the ECMs said they had never heard of that. Any comments?