- General Q & A
(https://www.offshoreonly.com/forums/general-q-20/)
- - 2004 496 HO Common failures?
(https://www.offshoreonly.com/forums/general-q/380523-2004-496-ho-common-failures.html)
87MirageIntruder
09-14-2023 03:07 PM
Originally Posted by BadDog
(Post 4879877)
Regarding the IAC taking out the ECM IIRC there were some threads about adding a fuse to the IAC to prevent this. I believe it was as simple as just putting a 1 (maybe less or more) amp fuse inline with the IAC power. Can anyone expand on this or was it limited to a certain package or all IAC equipment engines?
Marine Design Corp makes the IAC survival harness kits. These will fit the 496 also.
From their website:The Marine Design Corporation IAC Survival Kit is designed specifically for Mercury Racing 600SCi, 662SCi and 700SCi engines. Our kit eliminates costly PCM damage that can occur when an IAC fails, which can be a common occurrence. The kit was developed for twin engine applications and includes two plug-and-play IAC harnesses that are fused to prevent a direct short to the PCM. Also included are two Tier 1 OEM IAC units with gaskets, spare fuses and a canvas storage pouch. Replacement IACs and fuses are also available.
The IAC Harnesses only kit will fit the above engines as well as the 496MAG, 496MAG HO, 525EFI, 850SCi, 1075/1200SCi
BadDog
09-15-2023 05:15 AM
So whatever failure mode the listed engines have other Merc MPI models will not have a risk of the ECM failure due to IAC? I wonder what specifically the difference is that would cause the IAC to, presumably, draw too much current and damage the ECM.
87MirageIntruder
09-15-2023 09:45 AM
I'm not certain on that, but I do know the engines that run the PCM555 Motorola setup are very prone to damage from a failing IAC valve.
