carb flooding

[marcsin]

I have I/O 3.0L merc motor. When I run the engine hard ie towing water skiers etc and then turn off engine, upon restarting the carb seems to be in a flood mode. To start I need to advance the throttle to allow more air in the carb before I turn the ignition. On occassion, I have check to see if the choke valve is stuck and it doesn't appear to be. Twice, I have taken the boat in to marine repair shop where they ran the engine until hot trying to reproduce the problem unsuccessfully. Both times I was told that the carb is working fine. Any thoughts as to what else I should be looking at?

 

[petryshyn]

Re: carb flooding

Hi marcsin<br /><br />Seeing as how you are in Canada, I don't expect you'll be trying this any time soon.<br /><br />Next time you run the engine hard, let it idle for several minutes before shutting her down. <br />A possibility of 'Percolation' is occuring. The heat within the engine rises and accumulates near the carb and intake area due to convection. This heat can be enough to cause the fuel in the carb float bowl to boil. The fumes from the boiling fuel are channeled on some engines, directly into the intake, where they will condense back into liquid fuel over time. This liquid fuel is in addition to the fuel supplied when attempting to restart. The two fuels added together cause a over-rich or flooded condition. Thick base gaskets have been added under the carb to reduce heat transfer from manifold to carb in attempt at keeping the carb cooler. Electric ventilation fans have been added to the doghouse which tends to help by getting rid of this high heat soak as well.(make sure yours is working). EGR valves disconnected can promote higher temperatures. If the engine has a preheated air inlet, and it is stuck in the hot position, percolation can occur. Alcohol based fuels or additives also cause percolation at lower temperatures. (avoid Mohawk and gasline A/F) All of these affects can cause hard starting after driven hard. Left over winter fuel is a definate no no. Most of the above (except fuel type) can be overcome by idling the engine for 5 minute before shutting down. This allows the engine to cool, the fan has more time to rid the doghouse of the high heat accumulation, and the bulk of the heat build-up will leave via the cooling system, rather than by convection.<br /><br />This ofcourse is only one possibility.....Its all I'm capable since I got this bad Flu...<br />Others will have more.....<br /><br />Good luck!

 

[DJ]

Re: carb flooding

Schematic's got it, "fuels a perc'n." The phenom. is more prevelent in high acohol content fuels. I believe you have a lot of high ethenol fuels in Canada.

 

[ODDD1]

Re: carb flooding

Marcsin, I have run into a number of 3.0's with this sneaky problem...the motor is actually flooding, but you might not see it, and it will happen after shut down, too.<br /> even on engines that are not percolating,[fuel in float bowl gets so hot that it boils out the bowl vent and floods the motor]will flood, here is what happens...the float level is too high inside the carb, this elevated level will be fine most of the time, but in small boats, the kind that have 3 liters in them, if you shut the motor off and sit on the starboard side of the boat, this elevates the fuel level over the discharge tubes in the carb throat and fuel drips out down into the motor, flooding it.to verify, next time you run the boat turn it off in the water and quickly remove the flame arrestor and look down the carb...anything dripping is not good....

 

[dick]

Re: carb flooding

Try leaving your blower on after a hard ride ,schematic mybe right , heat build up from the engine can cause this.What type of boat do you have and does it have closed cooling?

 

[marcsin]

Re: carb flooding

Thanks all for your replies. Much appreciated. I now have a better appreciation as to what may be happening.