Well that escalated quickly!

[g36]

my bet is the oberg ufo filters being clogged. sounds like the exact issues with these when they wont pass fuel .

[Jlubas]

This all makes sense. I will look for the additional filters. Do any of you know if there is recors on this and if so where?

[waybomb]

You said you changed the ones that look like oil filters?
Some call those, generically, Racor.

Typically an oil filter looking device with a screw on bowl to catch water on the bottom.

Sometimes that bowl is clear plastic, sometimes metal.

[waybomb]

G36, did you get it fixed?

[SanJuanDreamer]

Like mentioned about, I'm sure you have more then one filter.
On my 98 454xLi, there are three on each engine. The Oberg filter, Racor 110 fuel\water filter and the barrel fuel filter.
Start with finding and cleaning\replacing fuel filters.

[Roxanne]

I know I'm new to this and just a girl but we have the same problem. SO FRUSTRATING!!! With ours it appears to be vapor lock. The starboard engine runs 180-200F. We've replaced the impeller and brought the temp down. The Mercruiser 454 have a history of this problem. (Google lol). The engines are designed to run 160F. The engine compartment shouldn't be hotter that 145F. If the engine is running hotter than normal, and the blowers aren't able to dissapate the heat the engine compartment rises above the ideal temp. It takes about an hour after you shut down the engines for the compartment to reach the full heat saturation which causes the fuel to go from liquid to vapor. That's vapor lock. On the short term you can open the engine compartment and run the blowers to release the heat. Ideally you should make sure your blowers are working and unrestricted. You should continue to run the blowers for 20-30 minutes after you have turned off the engines to reduce the heat saturation as mentioned above. In conclusion make sure you have the right size blowers, they are unblocked. Engines are running 160 or below. After all of this you still have an issue let me know. Mike can walk you through what we went through to resolve our issues. Good luck, and hang in there. They are great boats!!

[km1125]

Roxanne, are you still having the problem?

Source of the post
The starboard engine runs 180-200F. We've replaced the impeller and brought the temp down.

When you "brought the temperature down", did it get down to 180-200, or is it now closer to 160?? (later you say 'engines are running 160 or below').

These are all EFI engines right?? They should not really have vapor lock as the gas is under pressure... different from a carb system where there is little pressure and a vacuum pulling fuel from the tank. Perhaps you have leaking pressure regulators?? Did you ever check fuel pressure on the rail after the engine is shut down?

[Viper]

....These are all EFI engines right?? They should not really have vapor lock as the gas is under pressure... different from a carb system where there is little pressure and a vacuum pulling fuel from the tank.....

Not necessarily true. Even on EFI, you can get vapour lock. There's already a vacuum on the suction side of the fuel delivery system which is a contributor to vapour lock. Under normal operating conditions, the amount of vacuum isn't enough to cause the problem, but add enough heat, and the combination of the two on that side will cause issues, hence the introduction of liquid cooled fuel systems like Cool Fuel on Merc EFI apps.

Vapour lock has some very definite symptoms. If the symptoms don't meet the criteria, it's likely not vapour lock but something else. And a hot running engine doesn't necessarily mean you'll have vapour lock or that your engine compartment temps will reach unacceptable levels. Some engines run with 180* stats. I wouldn't say it's a Merc 454 problem. Under the right conditions, it'll happen with any brand. You'll just read more about the Merc 454 because there's more of them out there than all the other brands combined!

[km1125]

I realize it's POSSIBLE with an EFI system, but much more unlikely **provided** everything is operating like it should be. If you have too stubborn of an anti-siphon valve or excessive temps in the engine those are things that should be resolved.

I suspect that many of these problems would be traced to defective pressure regulators or a problem in the cool-fuel system.

If I had an engine that might be susceptible to a vapor lock condition, I'd consider adding a return fuel line to the tank, or a low pressure pump just after the anti-siphon valve. Maintaining even a slight pressure in the system is one of the big keys into stopping the fuel from vaporizing, just like a radiator cap stops the coolant from boiling.

[mjk1040]

Well I can only find 2 fuel filters on our 1998 Crusaders. Oberg and rancor cartridge water separator. Anyone know where the Oberg is located for the rear auxiliary tank, I do not recall seeing it?