Just found out the hours on my ECU are 151. Hour meter says over 400 which seems more in line with a 1995 freshwater boat. Can the hours be reset in the ECU with a reflash or are they permanent. I was allways under the impression that they could not be changed.

No they cannot. They are rom memory which is non-erasable. The hours do not add up when key is just on either. They operate off of a speed signal from the distributor, which is sent to the ecm. Your gauge hour meters are probably wired to ignition on witch is not the most accurate. Gauge hour meters should be wired up to a oil psi switch for the most accurate reading.

unless the ECU was changed.

or you left the key on your iginition on while docked and so forth.

I believe mine were changed. I had Gen 5 engines rebuilt by Tyler Crockett and he put whipplesa on them, They showed ony 50 hrs on them afterthe first season. They had to be reset. From what I hear only a few people in the US have the ability/security codes to re-program them.

Like Puder said they could be switched.

The hours "follow" the ECU. If the ECUs have been swapped out then the hourlog in them doesn't mean a thing.

Spoke with Dustin today and he told me that absolutley the hours logged on an ECU are unchangeable but sometimes they are inaccurate at the rate they record time giving false readings.