454 MAG MPI Starting Issues
 

Yesterday I had some issues starting the boat that I haven't experienced before. At the launch I had to crank the engine for 5-10 seconds to get it to start. Normally it fires right up. I idled out of the channel, turned the boat off for a few minutes and it did the same thing when restarting, but was up to temperature this time. We went for a short cruise and headed to the sand bar for the day. When it was time to go home, probably 4 hours later, it wouldn't start again and I had to give it throttle to get the engine to start. Once running it acted completely normal. When it does start it seems to idle high, maybe 1000 rpm for 10-15 seconds before it settles down to it's normal idle.

I've read some posts that make it sound like it may be the IAC valve, but those sounded like cold start issues. Would the IAC cause this issues during hot starts as well?

Engine is a 454 Mag MPI, Serial #OL632389

I'm not sure if it is at all related, but I did just put a new fuel sender in since the last time I ran the boat.

Thanks!

After researching a bit more, it looks like the fuel pressure regulator and associated vacuum lines are another place I need to check. Hopefully I'll be able to get in the the boat this weekend to try and diagnose some more. Anything else I should be looking at that may cause these symptoms?

Thanks

When cranking see if the tach comes up to around 300 rpm or so.
Fuel pressure should be 43 psi