What to do

[gatrboy52]

I've been looking at a boat with a 97' 200 efi. It was rebuilt and at times will run ok until 4 k rpm then a alarm. At other times it won't hardly run at all. I did I all I knew to do but couldn't get anywhere. I took it to my mercury dealer and he's telling me the computer is wack and needs to be rebuilt or replaced. So I'm weighing my options. Are used computers hard to come by or should owner have this one rebuilt? Thanks for any insight

[JOE54]

seek another diagnostic opinion , but they can be repaired , unlikely thats your problem

[gatrboy52]

This is a long time trusted dealer. If his computer is telling him the computer is bad what else could another dealer do he can't

[JOE54]

were all other components DVA volt tested on the water when problem occurs as well as fuel psi test , hard to see it run fine to 4000 with ecu driver bad , which alarm are you hearing oil or overheat ???? respectfully i have replaced literaly hundreds of CUMMINS ECUs on MERCURY engine and none of the failed ones caused an alarm ,,,suggest you obtain a known good ECU and install for a test ,,,, any idea of computer diagnostics used to determine failed ECU ???? please report back with findings

[EuropeanAM]

^^^^ There is no computer that "is telling him the computer is bad". There are two ways of identifying:

1. DVA readings to confirm the output of a driver is out of range, or non-existent

2. Trying a known-good ECU to prove the problem ceased.

These ECU's can be (and should be) repaired if failing. A properly repaired ECU is far more likely to provide years of good service than any "used" (perhaps even new) one.

[gatrboy52]

Computer shows triggers A B C bad. timing is off as is linkage. He can't address alarm until engine is calibrated correctly.

[JOE54]

sounds good

[EuropeanAM]

Computer shows triggers A B C bad.

If you get the chance, see if he can tell you what type of computer that is.