Re: Merc 7.4L (454) MPI Fuel Pressure
Fireman,
What's your particular issue?
I had an issue with my Mag MPI (454) where it was down on power.
I didn't know it for a while as the previous owner had "adjusted" the tach to read higher RPM that actual. Once I put a GPS on it, I knew I had an issue.
I have a 1998 MPI, which I believe is MEFI-1. The self diagnostics are very limited. I do have the scan tool (now), but the boat showed no diagnostic errors.
To find it, the boat had to be run on a hose - either the injector clips are hard to get to, so you'll basically need to pull the plug wires one at a time. Each plug wire should result in a drop in RPM.
Reading the plugs can tell you also...
It's very odd (in my experience) for an injector to die.. I'm new to the marine stuff. The shop that ended up working on my boat replaced the injector (around $200 for a single injector) - I really don't know if it was dirty or dead, I still need to get back there and ask.
There's a guy on the web that does great work with injectors, inexpensive, and he'll replace the pintle caps and rubber gaskets for under $20/each: ("www.witchhunter.com")
I'm curious about this also because I'm still chasing another 6-7mph top end on my boat. It's running 61-62 on GPS, rather than the 68.5 that was tested in original reviews. I might not have any issues at all, but to figure it out for sure, I'm considering putting it on a dyno. The bad news is that the dyno run costs around $300, $400 with air/fuel readings... Pretty expensive...
email me directly if you'd like:
d_ginther@hotmail.com