Gas fume smell

[4bw]

I am getting periodic gas fume smells on start up and when running. I changed the fuel filter, tightened every hose clamp on the fuel system, and cleaned the bilge to no avail. Any ideas?

2003 22v RE with Merc 350 mag mpi tow sport engine
Idle air valve was replaced last year, has new cap and rotor and plugs, all maintenance is done on proper schedule.

[boatwakes]

Do you think the fumes are from the exhaust like unburned fuel or actual raw gas smell?

[4bw]

Not sure on that, I have a FAE on the exhaust, but it may very well unburned fuel. What should I check if that is the case?

it is a very strong gas smell that comes and goes. I have noticed it occasionally for a while but once I started noticing it at start up that got my attention.

[boatwakes]

Has your fuel consumption increased recently but you're running the same amount of time? Is there a floating black particulate noticeable in the water upon any start up? Any exhaust smoke at cold start?
If it's in the exhaust you are looking at either a malfunctioning coolant temperature sensor, a malfunctioning fuel pressure regulator or a possible stuck injector. You can use an EFI fuel pressure tester connected at the engine front of the fuel rail to determine if its the regulator or injector. Connect the pressure tester and turn the key to the "ON" position and do not start. The fuel pressure should read in the vicinity of 30-34psi when the fuel pump cycles then HOLD that relative pressure for at least a minute. If it dies off immediately the problem is a stuck injector. If it holds correctly, start the engine and watch the fuel pressure. It should be + - 2psi from 32psi. Higher indicates the regulator is stuck and lower means your fuel pump is getting ready to call it quits. Keep us posted.

[boatwakes]

Also, I know you probably have already, but check for gas in the bilge, that's a game changer.

[4bw]

Thanks boat wakes I will check these out this weekend

[4bw]

Boatwakes et al

Have run the boat a few times, seems good except occasional fuel fume smell and I did notice the exhaust is white at times.

I got Fuel pressure gauge, key on, no start pressure is 40 and holds there
when started on fake a lake fuel pressure stayed at 40

I checked all the spark plugs and they look good and I checked the gap to confirm they were all at .060 per Merc They were all pretty close.

I will run the boat tomorrow and check the fuel pressure again.

From last post it sounds like the pressure regulator is stuck, if this is the case what is the next step to repair?

Thank you so much for all the help and knowledge.

[4bw]

just checked some specs and they said fuel pressure at 1800 rpm should be 43

This is the 2003 5.7l 350 mag mpi I/B Tow serial # OM317311

[boatwakes]

Your fuel pressure is perfect, it's +- 2psi and when the regulators go out they shoot up to 90-100psi, lower fuel pressure means the pump is failing and your serial number has the updated higher pressure pump. White steam is a sign of raw water blockage in the cooling system. Take these steps to ensure you're cooling system is fully flowing: if you haven't yet, remove the raw water pump from the engine and change the impeller. While the pump is off, back flush the cooling system: remove the raw water inlet hose at the thermostat housing, it's the hose coming in the front right of the housing as you're looking at the front of the engine. Attach a garden hose to this hose and blow out any impeller and debris remnants. Pull the hoses off the bottom of the exhaust manifolds and let them drain.