2010 F40LA Stalling Issue

[SkipJones]

My 2010 Yamaha F40LA has 275 hours on it-a mix of salt and freshwater use. The engine was tuned up last year. This year it has begun intermittent stalling when shifted into gear-forward or reverse. When placed in neutral and attempting to rev the engine out of gear, it also stalls. Once it stalls it is very hard to re-start. This condition is intermittent-at other times it will start and run fine with no stalling and no hard starting. This condition can occur when the engine is first started in the morning, and has also occurred after an our or so of running, then shut down, and attempted to restart an hour or so later. We are running fresh fuel. The stalling issue has caused us to be stranded and towed in twice-very frustrating. Thanks in advance for any assistance-
Skip

[rejesterd]

Hey Skip - Is it ever hard to get started first thing in the morning? When you say "This condition can occur when the engine is first started in the morning", does that mean sometimes it will stall when you put it into gear after having just started it for the first time that morning?

That's something to think about, because if it stalls when put into gear before the engine has warmed up, then you know it's not directly related to heat.

Also, do you get up to top-speed without any issues?

[SkipJones]

rejesterd,
Thanks for your reply-the condition occurs most frequently after the engine has been run and is at operating temperature. When not exhibiting the stalling/hard starting issue, the engine runs fine and turns WOT RPM (5800) and accelerates smoothly. Based on follow on research here and at www.thehulltruth.com, I'm leaning towards a problem with the fuel cooler, but certainly appreciate any other thoughts on troubleshooting...
Thks much
Skip

[rejesterd]

When placed in neutral and attempting to rev the engine out of gear, it also stalls. Once it stalls it is very hard to re-start.

The hard-to-restart symptom is the one I would focus on. It could mean that the fuel is boiling inside the lines and causing vapor lock, or it's flooding (possibly due to stuck open injectors).

[Captain ad]

Hi I'm having the same issues with my 60hp.
What iv'e found on mine is the fuel line that came with it was off a mariner and has an inner inner which was breaking down. At first we thought it was collapsing and stopping fuel flowing freely.
When I took the fuel connector to the engine off I could see small pieces of what I thought was varnish but it turned out to be the broken down bits of liner so I've renewed the whole fuel line and bulb.
I decided to look in the filter bowl before the fuel pump and sure enough bits in there also, checked the filter itself and could fine micro particles in-between veins.
Followed fuel line up to the inline filter just past the pump and you guessed it blocked with micro particles.
So I swayed to change the injector filter baskets to be sure,'ve actually just posted to find part numbers for them.
if they are blocked I may as well check the filter in the high pressure pump.
Does anyone know if there is any more hidden away somewhere.

[rejesterd]

Hi I'm having the same issues with my 60hp.
What iv'e found on mine is the fuel line that came with it was off a mariner and has an inner inner which was breaking down. At first we thought it was collapsing and stopping fuel flowing freely.
When I took the fuel connector to the engine off I could see small pieces of what I thought was varnish but it turned out to be the broken down bits of liner so I've renewed the whole fuel line and bulb.
I decided to look in the filter bowl before the fuel pump and sure enough bits in there also, checked the filter itself and could fine micro particles in-between veins.
Followed fuel line up to the inline filter just past the pump and you guessed it blocked with micro particles.
So I swayed to change the injector filter baskets to be sure,'ve actually just posted to find part numbers for them.
if they are blocked I may as well check the filter in the high pressure pump.
Does anyone know if there is any more hidden away somewhere.

I had the same thing happen to me last year, where I found black bits from a rotting fuel line in my filter cup. However, I saw none when I drained the VST chamber. You can try the same instead of taking it apart just to get a look at the internal filter. If you find no black bits coming out, then this might not be related to your issues. Note that I had no known issues when I found the black bits in my filter cup.. I was just doing my regular yearly maintenance.

As for basket part numbers, I don't think Yamaha will give you those. It's probably an industry standard size, but I don't know the exact specs because I just send mine in to be cleaned by a pro (who will replace the baskets as part of the service).

[SkipJones]

Thanks for all the inputs--fuel cooler is clean. Moving on to the next items to troubleshoot. We used the boat this past Saturday and the engine exhibited the same symptoms--started easily and ran smoothly for 30 minutes-from idle to WOT RPM with two adults aboard. Came back to the dock, tied it up, and tried to start it an hour later and it turns over, but will not start. Tried squeezing the primer bulb and that got it to fire, but would not run. Very, very frustrating. Hate to start throwing parts (fuel pump, etc) at the problem.

[rejesterd]

If you don't want to blindly replace any parts, then you have to diagnose it (which will probably mean you need to buy some tools/gauges that are more expensive than the parts you're testing). Have you checked the operating temperature 5 minutes after the first start of the day and then again when you shut down the engine (before the issue occurs)? What does the impeller look like? How about the thermostat.. does it open at the expected temperature (usually printed on the thermostat itself)? And have you ever had the injectors professionally cleaned? Have you verified that the vapor solenoid valve is closing after you shut down the hot engine? Those are the components I'd be looking at.

[SkipJones]

Thanks for your reply-impeller is replaced annually. Have not had the injectors cleaned and will ask our mechanic to check the vapor solenoid valve-