4.3l Mercruiser bogs and stalls

[95eclipse]

4.3L Merc. 2bbl Mercarb. New plugs, cap, rotor, wires. Ran great for 10 mins at 25-30mph. Then backfires. Will run at idle afterwards but will eventually "load up" and stall out. It acts like it's starving for fuel but then acts like it's flooding at idle. After waiting a few minutes can restart and begin routine again, at idle still or slightly above. New water seperator filter.<br /><br />I want to drain the tank and start fresh. Tank has never been run empty in 9years. What is the best way to empty the tank? 95 wellcraft V-hull.<br /><br />Any suggestions and recomendations are greatly appreciated.

 

[Don S]

Re: 4.3l Mercruiser bogs and stalls

Sounds a lot like a plugged air vent to the fuel tank.<br />Could also be partially plugged screen on fuel tank pickup or antisiphon valve.<br />Or water in the fuel filter and carb.

 

[95eclipse]

Re: 4.3l Mercruiser bogs and stalls

Thank you for your reply. I've replaced the antisiphon valve with a strait through nipple. That's what I thought it was first, could barely suck or blow through it either way. How much pressure should the fuel pump produce? Does it run all the time or only when there's a demand? What is the best way to remove water from the tank? So many questions... Thanks again

 

[waterone1@aol.com]

Re: 4.3l Mercruiser bogs and stalls

Eclipse, I'm all for testing things, but you really should replace the anti-siphon valve, now that you know it is not causing your problem. The fuel pump should be running anytime the engine is. If the boat has been sitting for a while, any water should be settled at the bottom of the tank, you can use any manual method to suck out the bottom of the tank. If you use any kind of pump to do this, make sure it is rated for fuel use (ignition protected, and rated for gas).

 

[95eclipse]

Re: 4.3l Mercruiser bogs and stalls

I removed the fuel filter and poured the contents into a glass jar, no water appeared. The fuel looks good. How much pressure should the pump produce and how to you check that pressure. I have confirmed also that the oil pressure switch is working, at least I show 12volts at the pump while the engine is running. Do you normally hear the fuel pump running? I don't hear it or feel any vibration on it. Thanks for any input.

 

[95eclipse]

Re: 4.3l Mercruiser bogs and stalls

Also removed the fuel line and vent lines, all clear. Inspected the fuel filter at the carb and also is clean.