Mercruiser 7.4L MPI slowing down
08-01-2019, 12:11 PM
#61
Registered
Check all hose clamps on exhaust for damage and tightness. Check all hoses , boots , y-pipe , and manifold gaskets for leakage. F/I engines run clean , so can be hard to find exhaust leaks. I've had to spray a little fogging oil in intake while running to create some smoke to make leaks visible. Good luck.
08-01-2019, 01:17 PM
#62
08-02-2019, 11:17 PM
#63
Check all hose clamps on exhaust for damage and tightness. Check all hoses , boots , y-pipe , and manifold gaskets for leakage. F/I engines run clean , so can be hard to find exhaust leaks. I've had to spray a little fogging oil in intake while running to create some smoke to make leaks visible. Good luck.
At this point the mechanic thinks the only thing that it could be is the ECM. I did ask about exhaust and ventilation and he said that he ran it again with hatchclosed until it occurred but this time when he opened the hatch it did not clear issue - apparently it was pretty warm outside (so if it was the air getting in there it would have cleared it so it appears to be a thermal issue.)
He spoke to Mercruiser also and they said it’s symptomatic of a bad ECM. Mercruiser doesn’t have that available but MEFIburn.com rebuilds them and my mechanic said he spoke to mefiburn and the rep told him to pour cold water over the ECM and he would know right away if that’s the issue. I have heard of using Freeze it on the ECM, but could water just short it out (water and electronics)? It sounds like the mechanic might not be able to test it over the weekend, is this something that I could try myself? I can see what the ECM looks like from the Mercury parts site with my engine SN, but it doesn’t show where ECM is. Is that easy to get to? I have no idea where it is. If I could find it I could test that myself to try and speed things up.
Thanks,
Scott
08-03-2019, 07:07 AM
#64
Registered
iTrader: (1)
He spoke to Mercruiser also and they said it’s symptomatic of a bad ECM. Mercruiser doesn’t have that available but MEFIburn.com rebuilds them and my mechanic said he spoke to mefiburn and the rep told him to pour cold water over the ECM and he would know right away if that’s the issue. I have heard of using Freeze it on the ECM, but could water just short it out (water and electronics)? It sounds like the mechanic might not be able to test it over the weekend, is this something that I could try myself? I can see what the ECM looks like from the Mercury parts site with my engine SN, but it doesn’t show where ECM is. Is that easy to get to? I have no idea where it is. If I could find it I could test that myself to try and speed things up.
08-03-2019, 06:16 PM
#66
Registered
Personally I cannot imagine pouring cold water onto anything in an engine compartment, especially when it is hot. You should be able to find the Freeze It spray, that is what I would use.
08-03-2019, 11:12 PM
#67
08-04-2019, 11:11 AM
#68
Registered
What's a Boat-In-A-Box?
Gotta try this Freeze-It stuff too. Same engines as you and I've been chasing a hot idle problem for years to no avail. Left with some ignition parts to swap, injectors to send for testing (last resort) and ECU. ECU was out at Mefiburn about a year ago though and bench tested OK.
Keith
Gotta try this Freeze-It stuff too. Same engines as you and I've been chasing a hot idle problem for years to no avail. Left with some ignition parts to swap, injectors to send for testing (last resort) and ECU. ECU was out at Mefiburn about a year ago though and bench tested OK.
Keith
08-04-2019, 02:14 PM
#69
What's a Boat-In-A-Box?
Gotta try this Freeze-It stuff too. Same engines as you and I've been chasing a hot idle problem for years to no avail. Left with some ignition parts to swap, injectors to send for testing (last resort) and ECU. ECU was out at Mefiburn about a year ago though and bench tested OK.
Keith
Gotta try this Freeze-It stuff too. Same engines as you and I've been chasing a hot idle problem for years to no avail. Left with some ignition parts to swap, injectors to send for testing (last resort) and ECU. ECU was out at Mefiburn about a year ago though and bench tested OK.
Keith
Who makes freeze-it? When I google it I get hair spray. Does it cool to -65 if so it’s probably the same as an autozone type of freeze spray. This is called freeze off:
https://m.autozone.com/greases-and-g...1-5oz/898352_0
is that the same type of spray?
08-04-2019, 06:44 PM
#70
Registered
This is called freeze off:
https://m.autozone.com/greases-and-g...1-5oz/898352_0
is that the same type of spray?
