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.

Re: Stall issue
 

Paul I may be wrong, but engine temp of 140 degrees makes a fuel boiling problem hard for me to believe. It is possible but you may have something else going on. Does it ever stall when moving at idle speed while the engine is at operating temps? I read in a post in another part of the forum that a bad ignition coil can cause a stalling issue when an engine is warm. The forum member theeasynine tracked what he thought was a fuel boiling problem down to high engine temps being cause by a lean running condition(he has fuel injection though). Like I said I may be wrong, but 140 degree engine temp in my opinion would not create fuel boiling conditions. Let me know if you find something else. Hope that helps.
Happy Boating
Dan

Re: Stall issue
 

The stall occurs after the engine has sat for a while after being run.

It will only stall one time one to three minutes after a restart and then it runs fine.
It will stall just sitting out of gear idling, it will stall when you put it in gear.

So I've been starting it at the dock, letting it idle till it stalls. Restart and I'm good to go unitil I shut it off again.

Re: Stall issue
 

Do you just bump the key and it starts right back up, or do you have to open the throttle? If so how far do you have to open the throttle? I read in one of your earlier posts that you had to floor the throttle before because of a flooded condition. What is your idle RPM?
Happy Boating
Dan

Re: Stall issue
 

I have a 2001 z212 with a merc 350 fuel injected and had a vapor lock problem which surprised me because I assumed with fuel injection I did not have to worry about vapor locking. Could not get to restart so had to be pulled in, the following morning it started right up. Went to the boat shop and the mechanic said to add sta-bil fuel treatment and it would cure the problem. He gave me a 16 oz. bottle to start out with and had me add half the bottle to 3/4 of a tank of gas to get it going in the fuel system. Then went to regular 1oz. per 10 gallons for maintenance. Problem solved no more vapor locking. Fuel system can not be over treated with sta-bil. The cheapest fix I have ever had.

Re: Stall issue
 

Don't remember what my idle RPM is, but it was below what is was supposed to be and I had the mechanic adjust it last year.

Pretty much turn the key and go.

Sometime I have to give it a little gas, but not usually.

This weekend, when it stalled, just turned the key and it starts back up. There have been times when I fiddled with the throttle and ending up flooring it to get it to go.

Re: Stall issue
 

I would make sure the fuel filters are fresh. I would also probably check the ignition timing, but I am still thinking a float sticking issue, or trash/varnish deposit in the carb. A carb kit may be in order. Hope this helps
Happy Boating
Dan