1998 210 Signature BR with 5.0...

[Jimmie]

1998 210 Signature BR with 5.0 Mercruiser EFI, was on the lake and had stopped for lunch for approximately 30 minutes but when finished lunch I started motor with no issue only it stopped within 5 seconds. On every subsequent attempt to start motor it would fire and immediately cut off. Interestingly while being towed to dock, I attempted to start motor and it started and ran fine all the way to dock never any issues prior to this. At dock I stopped and successfully restarted it once while loading. Has anyone experienced this issue?  What should I do preventively before our next outing? 

[wingless]

Welcome to the forum.

The symptoms sound like heat soak vapor lock.

If this is the problem, then Mercruiser has an expensive solution, adding a low pressure pump before the fuel pump to "burp" out the vapor, permitting the engine to start, hiding the problem.

The engine compartment is insulated, to contain audible noise, for better experience when boating. That insulation also contains heat, causing the engine compartment temperature to spike when the engine is shut down, frequently the cause of heat soak vapor lock, with the conditions described.

On my boat I designed and installed a thermostatically controlled high volume heat exhaust system that maintains the engine room temperature and has eliminated the problem.

[Jimmie]

Thank you wingless and I will explore that option for mine as well.

[wingless]

YW, the "easy" option is to use the boat, make a ~1 hour stop, but with the engine compartment wide open, so all the heat is free to escape. If it starts normally, but doesn't start under the same conditions w/ the hatch closed, that also points to heat soak vapor lock.

Another test is to connect a fuel pressure gauge to the fuel rail. If the pressure is abnormal during the problem, then it is definitely heat soak vapor lock.

[Captain_Zero]

On the older 5.0 efi the ignition coil on back side of motor is a common failure as well. There is also a small processor on the distributor itself that can misbehave when hot

[denisehalstead]

We are having the exact same problem on a 2002 Sea Ray 185 bowlder with a 4.3 Mercruiser MPI. We had it happen several times while on an extended trip visiting different lakes. Also would restart as we were being towed or after it sat for awhile. We have it in the shop now.

[Jimmie]

Please let me know what you find out from the shop and post for information. Mine hadn’t done it again until today and after sitting for a while it started and ran fine.

[wingless]

Jimmie, was the fuel pressure measured w/ a gauge during the problem, results?

Was the boat stopped for ~1hr w/ the engine compartment open to determine if the problem exists, results?

[denisehalstead]

I will definitely post what I find out. I have heard on The Stream at large that an inline fuel pump or cooled fuel pump is something that has been a fix for this engine. I heard its installed before the regular fuel pump. I'll post when I know for sure!

[215_Express_Cru]

Why not just run the blower that is located in the engine compartment for a few minutes before starting the engine?

[wingless]

215 Express Cruiser, welcome to the forum.

My experience is that the OEM blowers had zero effect on heat soak vapor lock.

Those blowers must suck from the bottom of the engine compartment, to draw the heavier than air gasoline fumes, if they ever exist.

But, heat rises and the engines have a huge thermal mass.

Once the engines are stopped the cooling water flow also stops, so the engine compartment temperature rises.

On my custom thermostatically controlled heat exhaust system, I draw warm air from the top of the engine compartment to maintain a constant temperature.

[215_Express_Cru]

Ahhhh Haaaa ...... That makes perfect sense... Forgot what i learned in my seventh grade science class Warm Air Rises....