MPI Starting

I have 2 Merc MPI boats. One is a 2004 6.2 and the other with a 2006 5.7. Neither engine likes to start without the throttle being at "high idle" position. Other than that they both run perfect. No IAC codes.

Is this pretty normal or is something out of adjustment?

Neither is normal
Check voltages on the red/purple wire at the key when cranking

Bad Chokes ? Some water in both gasoline tanks and fuel systems ?

I’m no expert, but my old boat had a Merc TBI with electric fuel pump.
I discovered that the key needed to be on for about 5 seconds before cranking to allow the fuel pressure to come up.

alldodge said:

Neither is normal
Check voltages on the red/purple wire at the key when cranking

Click to expand...

I'll check that.

cyclops222 said:

Bad Chokes ? Some water in both gasoline tanks and fuel systems ?

Click to expand...

They are both fuel injected. No water in tanks.

FunInDuhSun said:

I’m no expert, but my old boat had a Merc TBI with electric fuel pump.
I discovered that the key needed to be on for about 5 seconds before cranking to allow the fuel pressure to come up.

Click to expand...

Maybe that has something to do with it.

Its just something I noticed the past several years with my 2004 6.2. I bought a 2006 last year and it starts the same way. They will both start without giving it throttle but most of they time they have a long crank time and sputter and die. When I click the throttle to the first click they will start fine.

I have a 3rd boat I keep at our vacation house that has a 4.3L fuel injected Volvo. That seems to start a lot better without opening the throttle.

check fuel pressure. you could have a leaking injector that is filling the intake manifold with fuel. the excessive fuel would be cleared by having the throttle open.

All of you EFI engine people could be having high and low Fuel Pressure Bled down over time. Opening the throttle a LOT will help pressure build up faster. As injectors age. They bleed off pressure faster.
1 of the reasons I like carbs & full float systems. Takes a couple of weeks to lower fuel level.
The Evinrudes do have a a solenoid that squirts liquid fuel into the carburetor throat. Starts cold in less than a second in hot weather.

Jesse and others.
Sounds like the idle setup is too lean and too slow. Move / have it adjusted it up that 1 click. And enjoy the boat.
All engines should always be adjusted to start instantly. Hot or cold. They rotate at least 500 rpm at idle cranking speed.

My 2004 Mag 350 MPI starts with no throttle. I've had it for 7 years and it's always been that way. Except, when I had a bad IAC and one other time recently I've never figured out but its never repeated either.

cyclops222 said:

Bad Chokes ? Some water in both gasoline tanks and fuel systems ?

Click to expand...

where is the choke on an mpi?

My Volvo Penta 5.7 MPI also (MEFI 4?) requires some throttle when starting otherwise it’s sputters and dies when first starting cold. Warm starts give no problems at all. I think I figured out if I leave the key on for a little bit, it gives the IAC stepper motor time to move from the hot, running position to the cold start position. I also just realized that I usually turn the battery switch fully off between outings, so it may be that the ECM doesn’t know where things are when power is removed from it between outings. The fuel pressure doesn’t drop at all while the engine is off for even a few days. I think this is telling me I probably need to replace the IAC valve because it’s not moving fast enough. I also noticed if I’m running fast and return the throttle to idle too fast it will sputter and die sometimes as well. The fuel pressure is 50 to 60 psi depending on manifold vacuum, which appears to be normal. The last boat I had used a throttle body injection MerCruiser and it just ran and started and stopped without issue. It seems that perhaps the MPI engines are a bit more persnickety.