Mercruiser 5.7 stalling problem

[jamesknechtel]

have a 1994 5.7 EFI mercruiser TBI, 339 original hours, boat stalls while trolling at idle, also in neutral stalls. Paid a local marina to check it over, they water tested after finding nothing at shop. They ran it hard. It did not fail for them. They charged me $793.00 Then i replaced small coil under distributor cap, still stalls at idle, then i replaced distrributor cap coil, still stalls. When it stalls, it turns over but will not re-start. I have to wait 10-15 minutes, then it will start, run for 1\2 hour, and stall again... It did this six times last time out. Right after stalls, i checked spark, lots of spark but wont restart for 10-15 minutes.. any ideas?

 

[Tassie 1]

Silly, silly question,
EFI?
carb?

l have two later model 5.7 mercruisers,
had a" similiar sounding " prob on one,

clean/ replace all filters,
on mine there is a foam filter behind a sensor that you need to take the flame arrestor off to get to

soak in water, let dry.

might not be your problem though,

should ask the question in the mercruiser section towards the bottom of the page.

you should get the correct answer there.

 

[Fun Times]

Hi there, welcome to iboats!

A few general thoughts to start off with could be you might be experiencing some sort of fuel vapor lock issue possibly due to excessive heat to possibly the VST (Vapor Separator Tank) that houses the EFI fuel pump side of the fuel system which is (can be) a hard issue to find even with an fuel pressure tester gauge connected....< Which should still be one of your tests to preform during the event so you know what/where the fuel pressure is.
http://www.mercruiserparts.com/bam/s...31869/1953/130
http://www.mercruiserparts.com/bam/s...31869/1953/120

You also have an mechanical fuel pump on the starboard side of the engine next to the fuel filter/water separator that could be going out too, http://www.mercruiserparts.com/bam/s.../31869/1953/90
Plus some engine models had an inline fuel filter between the fuel tank and engine connection so look for that on yours as well just in case.

Being TBI, you'll need a special fuel pressure tester connector adaptor Merc part number 91-806901 that goes inline of the throttle body fuel line.

Another possibility that may be happening is your fuel tank anti siphon valve has become (intermittently?) defective with some sort of debris, waterish type corrosion, etc. etc......Try by passing the boats fuel tank with a remote fuel tank and new hose and go for a boat ride or two as well.

Also when the engine doesn't start, try looking at the fuel spray pattern coming out of the 2 throttle body injectors....Also try and take note of the spray pattern when all seems normal both during engine cranking over (< before start up) and running modes.

Next time it won't start try opening the throttle handle slowly from 1/4 to near full throttle to see if giving the engine more air will help start the engine...The Idle Air Control Valve found on the throttle body might need a cleaning or replacement....I'd like to also mention that 1994 EFI engines didn't utilize the IAC foam filter yet.

Gasoline Engine Vapor Locking