I could really use some help, mine...

[DestinEd]

I could really use some help, mine is a 2005 Sundeck 200 with Merc 5.0: MPI and we enjoy the boat and don't really need anything more.  But, there is one problem that is incredibly annoying that I can't seem to trace down.  I have 2 Chevy 350s sitting in the garage and they start at the first turn of the key.  The boat normally starts a bit hard for a fuel injected engine and about 2 or 3 times a year it won't start at all and seems flooded to me.  It sits on a boat lift near Destin FL.

Here is the common scenario: it hasn't been started for 2-3 weeks and tries to start after cranking 2 or 3 seconds then sputters and dies.  From there it is almost certainly not going to start but continues to sputter when I try.  Once running it never has a problem or if it has recently ran its fine.  Plugs get replaced every year so I don't really think that is the problem.  Last summer I put a fuel pressure gauge on it but got strange readings although the engine was running at the time.  Could this be an injector problem?  What am I missing please?

[DestinEd]

FYI, the whole boat only has about 250 hours on it so I think the compression is not likely to be the problem.

[wingless]

It sounds like you are on the correct path. It sounds like a fuel issue. Bad compression would not get better.

Refer to the engine FSM. It will specify the fuel pressure, plus it frequently also specifies the fuel pressure bleed down w/ the engine off.

On mine, the fuel pressure is solid, running or static. On mine, there is a vacuum-controlled fuel pressure regulator, connected to a very poorly designed vacuum system. (I discovered that system needs thorough annual cleaning to maintain proper operation.)

Have the fuel filters been replaced?

Nothing wrong w/ getting fuel injectors tested and cleaned. I was having performance issues, sent all 16 out to a pro for cleaning and testing, he found several bad, plus poor operation on most / all.

After that injector service, plus other problem resolutions, my engines have been solid performers.

[DestinEd]

OK wingless, I think it makes sense to do the fuel system overhaul starting with the fuel filters and having the injectors serviced. Another detail, there are times when it seems to miss getting up to full throttle - if I add SeaFoam to the fuel the problem goes away for a while. I wonder if that stuff is helping the injectors limp along?

BTW, how do you monitor your engine FSM? I don't have a way to do that but could purchase a monitor if needed.

[wingless]

FSM is a generic acronym for Factory Service Manual. Each group of similar engines has a specific FSM w/ factory documentation for repairing / servicing / maintaining those engines.

The Engine Control Module (ECM) controls the engine, based on all the sensors, including the throttle position sensor, to provide proper operation.

There are diagnostic tools to interrogate / control the ECM. I use the Mercruiser Digital Diagnostic Terminal (DDT).


https://live.staticflickr.com/4357/36075822920_55df4c9044_c.jpg

[kilbrew]

Check your electric fuel valve. I've got the same setup and mine went at the end of last season. Had similar symptoms.

[DestinEd]

Kilbrew, I'm not familiar with the electric fuel valve. Was yours very intermittent like I've described? I'm looking into it, but thanks for the tip.

[cash]

I have the same boat so far no problems, less than 200 hours

[DestinEd]

After reading about it, it seems that you can bypass this valve. I guess that is the place to start. Is that a valid test?

[DestinEd]

Went out to test it today and now I have a starter problem, when I was cranking it all of a sudden it stopped and now nothing. I'll get back to this fuel issue after I fix the starter...