5.0 mercruiser lx runs at cruising speed for 5-10 min then dies

[bskrickis]

I have a 5.0 merc lx in a 20ft searay, and my issue is engine runs perfect on muffs and when I get it in the water starts right up no problem. let it idle until temp reaches 130 then take off. boat will run at slow speeds for a long while, will get it up on a plane and run at cruising speeds for 10-15 min then stalls right out. will not start back up again until it sits for a while. then starts right up. replaced fuel filter, same thing. thought it was bad fuel, ran on external tank fresh gas, same thing. cap, rotor, ign coil, starter solenoid, replaced last year. carb new 2 years ago. I am thinking its electrical not mechanical cause it seems when it heats up it wants to die. Any help or ideas would be appreciated.

 

[alldodge]

Welcome aboard
First guess is the tank is drawing a vacuum due to tank vent may be clogged. When boat stops loosen the gas cap and listen for air to be sucked in. If you hear air then that's what's doing it

 

[bskrickis]

Welcome aboard
First guess is the tank is drawing a vacuum due to tank vent may be clogged. When boat stops loosen the gas cap and listen for air to be sucked in. If you hear air then that's what's doing it

I ran the boat on an external 6gal tank with the vent wide open and same thing happened. Thank you for your reply. Could worn plugs possibly overheat and cause a misfire and stall, then when they cool down fire properly?

 

[alldodge]

What's you motor serial number?

 

[bskrickis]

What's you motor serial number?

OF 147124

 

[bskrickis]

could a bad fuel/air mixture be the reason for the stall. it almost seems like when its running cold its fine but after 8-10 minutes and the choke fully opens the air fuel ratio is off and it cuts out. Could the carb just need adjusting?

 

[Scott Danforth]

could a bad fuel/air mixture be the reason for the stall. it almost seems like when its running cold its fine but after 8-10 minutes and the choke fully opens the air fuel ratio is off and it cuts out. Could the carb just need adjusting?

Yes