[Brad97]

I almost forgot to ask about this, I have the 454mag in a Z222 and when I have been running the boat for more than 1/2 hour and stop for awhile it doesnt want to start, it's a mpi by the way. If I open up the throttle several times it barely starts but not always, this is not good for I do most of my boating on the Missiouri river which has a very strong current, it acts like the fuel is vaporizing any thoughts would be appreciated.

[ColoradoDiablo]

Hey Brad ,
Does it have the electric fuel pump with the fuel cooler? , Or is it the std mechanical pump?
Either way , first I'd check fuel filter and then fuel pressure.

[Brad97]

electric Larry if it sits for like a couple of hours it starts right up.

[ColoradoDiablo]

Brad check fuel pressure. It should be right at 43 psi. Leave the tester hooked up for about 10 min and see if it bleeds off very fast. Also pull the vacuum hose from the regulator and see if there is gas dripping out. If so , bad regulator. Check to see that the washer on the regulator fitting side is good also.
I'll do some more looking

[ColoradoDiablo]

Brad ,
Talking with one of my marine tech buddies........he suggests checking the regulator vacuum line for fuel also.
There was a technical sevice bulletin on the issue also. I'll see if I can find it.
There is also a Intake Air Sensor and a Throttle Position Sensor on your 454 mag.
Those plus the regulator aren't cheap.
I think if you can't remedy the situation with a fuel filter or checking the regulator , you need to take it to a Merc Tech so he can run a diagnostic on it. He can pull any codes from the ECM and pinpoint it. That will tell you for sure what is going on . and what needs to be replaced , if anything.

Just for giggles , when was the last time you gave her a tuneup?

[Brad97]

When I bought it back in May, Larry I was talking to a friend of mine who own's Quality Marine and he said this was a comon problem with Merc, I guess they make a secondary fuel pump you can install that cures the problem.