Mercruiser 4.3l stalls after restart / rest for 5-10 minutes

[Gregdufour]

Hi there. I have a 2006 four winns h180 with a Mercruiser 4.3l MCM. I have only just bought it. When I take it out first up in the day it runs beautifully. It runs at 175 degrees. We bring the boat in and turn off the engine for 5-10 minutes while we swap riders. When we take off again at half throttle getting a rider up the engine sits at 3000rpm 25Mph then stalls about 20 seconds after getting on plane. The engine cuts out. Restarts again and then runs fine until we stop at the beach next time with no more stalls. We then stop again for 5 -10 minutes to swap riders and it happens again. This is very regular. If i go slowly after a restart no problems. Only when I give it some. Have just had it serviced and the mechanic cant work it out. Any ideas? Greg

 

[tacx]

Check your fuel tank vent. It could be plugged. If its plugged, or partially plugged, your engine will run after it sits a bit, but will die when the air in the tank does not get replaced through the vent when running. At slow speeds the vent may be allowing enough air into the tank, but at higher speed it can't keep up with the fuel draw from the engine. Just a thought.

 

[alldodge]

Could use a serial number to verify
If fuel filter has not been changed do so.
Remove fuel line at carb (assume TKS) then remove connector nut and inspect strainer (item 29) behind it

https://www.mercruiserparts.com/bam/...31494/13798/80

If all good test the fuel pump pressure

 

[Gregdufour]

Thanks for your responses.
Serial no. is 0W627822.
I read somewhere else that it could be the pistons expanding when the boat is cooling down and shrink when heated. After the restart they don't expand quick enough. Could be the piston rings.Is this possible.

 

[alldodge]

Thanks for the SN
Yes you have a TKS carb and parts for the motor are here

https://www.mercruiserparts.com/4-3l-carb-alpha-bravo-0w310000-thru-0w

Thinking its a fuel supply issue, need to check the pressure

 

[Gregdufour]

I read somewhere else that it could be the pistons expanding when the boat is cooling down and shrink when heated. After the restart they don't expand quick enough. Could be the piston rings.Is this possible.

 

[alldodge]

I read somewhere else that it could be the pistons expanding when the boat is cooling down and shrink when heated. After the restart they don't expand quick enough. Could be the piston rings.Is this possible.

IMO no, heat expands and cold contracts (shrinks). There is also not much time in between stop and restart. Don't see how rings would cause the issue, and if rings were a problem then there would probably be other issues as burning oil

 

[Gregdufour]

Thanks. If its a fuel supply issue then why only just after the restart 20 seconds after getting on plane and not have the issue after that.

 

[alldodge]

Thanks. If its a fuel supply issue then why only just after the restart 20 seconds after getting on plane and not have the issue after that.

I can continue to make more guesses, but that's it, they are just guesses.

Is the fuel pressure low, does the carb start to flood when shut off, is there a fuel restriction? Other things come to mind

Right now, we are guessing, we need some testing to verify something so we have a starting point. You, your mechanic nor I do not know what is happening. Only your mechanic may have done some testing, I say may because there are good and no so good mechanics.

 

[Gregdufour]

Hi there,

Just an update on this issue. Had carb cleaned out and had under the distributor cap checked over (all this after initially having a full service). Still having this issue with stalling. Appears it doesn't happen till after an hour or so of boating. Only happens when the engine has been idling for some time. If it idles for a short time (ie when a wakeboarder falls off then turnaround and get them up again) then no issues. If i idle for a few minutes then stalls 10-15 seconds into giving gas. But doesnt stall after that until i idle for a few minutes again. If i dont idle for a few minutes then theres no problem

Also noticed that when it stalls, if i leave it in gear it cuts the motor out once the boat comes to a standstill. If i put it in neutral once it stalls the engines stays on but wont go again until the boat has come to a halt.

Any thoughts appreciated.

 

[Walt T]

It is vapor locking. Go to pure-gas.org and find a station near you that sells non ethanol fuel. That will cure it.

 

[alldodge]

It's fuel and need to know if your getting to much or to little, but I'm leaning that there is to much.

Have the motor up to temp as normal and remove the flame arrestor. Look down the carb and see if fuel is dripping

The TKS carb when cold has the enrichment valve open which allows more fuel. When the valve is open you will hear a louder hissing. Once the motor warms up the valve closes

Do you hear any of this hissing going on when warm?

 

[wahlejim]

Float may be malfunctioning in the carb. What did they do to clean the carb?

 

[Gregdufour]

It is vapor locking. Go to pure-gas.org and find a station near you that sells non ethanol fuel. That will cure it.

Thanks. I have been told by my mechanic to go with 91 unleaded fuel. I have been using 98 so that may be the issue. Will give this a go first. Cheers.

 

[alldodge]

It is not vapor lock, and going to higher octane fuel only cost you more money

 

[Walt T]

Classic vapor lock. no harm in filling up with alcohol free gas. free and easy.