Stall issue
 

Been having an issue with my 4.3 2bbl in this hot weather. It happens after I've been running and shut down for a while.
The boat will start back up, but will then stall usually in the first minute. Sometimes it will fire right back up, but I've had it flood on me also and I've had to floor the throttle to get it to go.

I think the fuel is boiling into the intake, but I'm wondering what the solution is.

Carb rebuild?

Re: Stall issue
 

Paul, if u are sure the problem is carb related it sounds like the float may be sticking. A rebuild may be in order, but I would first try cleaning the fuel system with Chemtool B-12 or Seafoam fuel treatment. If u can start it out of the water with muffs on the lower unit, you can spray B-12 with a straw through some of the vacuum ports while the engine is running. Be prepared for a backfire and please don't blow yourself up. The more indirect route would be to pour a fuel treatment into the tank and and run a tank of fuel through the engine. If that fails a carb rebuild may be in order. Just make sure you rule out any other problem before doing the carb rebuild. Hope this helps.

Happy Boating
Dan

Re: Stall issue
 

Still having this exact problem with mine. Had to get towed in Sunday. Vapor lock is happening but I have no clue how to stop it. We ran the tank almost empty and filled with no ethanol gas but that did not help. I believe the fuel tank breather is not clogged or pinched. Any help would be appreciated. Seems like more people at the lake would be having this problem but it seems like just me.

The lake where we go is a cooling reservoir for a power plant so the water temp is generally above 95 most of the summer so I know the engine runs hotter than it should. Maybe I'll try running blower the entire time we are anchored to see if the engine compartment cools down.

Do a google search for: Mercruiser service bulletin 99-7.

Re: Stall issue
 

I am a pilot and aircraft mechanic. The way we prevent vapor lock in planes that use auto fuel is to insulate fuel lines around hot areas and use an electric fuel pump on takeoff and landing. An electric inline pump would be easy to install.

Jeff B

Re: Stall issue
 

A simple test for a vapor locked fuel tank is to run the engine and get everything good and hot. Turn off the engine and open the fuel cap. If you here the "whoosh" sound of air rapidly entering the tank then u have a tank venting issue. If you have determined that the problem is fuel boiling or vapor locking in the engine compartment then the only way to fix it is to reduce the fuel temp in the engine compartment, larger blower, insulated fuel line, insulating spacer under the carb, etc. If you decided to modify something on your fuel system just make sure it is safe.

Happy Boating
Dan

Re: Stall issue
 

How would you control this inline pump? Does it pump all the time or do you wire it to a switch?

Re: Stall issue
 

Wire it to the ignition switch... hot/on wire.. when turned to the right..

Re: Stall issue
 

I added the fuel treatment and I also left the sundeck up while I was at the beach to let the heat escape.

It did not stall when I left the beach. It did stall later when I left the sunpad down at the dock, but started right back up.

The outside temperature was in the 80's instead of the upper 90's as well. The Mercruiser bulletin also suggested to run at idle for 3 to 5 minutes before shutting down.

I think if I can keep the heat down in the engine compartment, it will be a big help.

Re: Stall issue
 

One thing we have all forgot to ask is what is engine temperature? Just another possible piece of the puzzle.
Happy Boating
Dan

Re: Stall issue
 

It's been around 140 degrees.