8.1 Horizon Engine Issue

TheBobC

Member
Sep 21, 2017
79
Pompano Beach, FL
Boat Info
1999 400 DA
Garmin 1242xsv, 742xs, Fantom 24 Radar
Highfield 10.2 Tender w/Tohatsu 9.9
Engines
Cat 3116
I am having an issue with the port engine on my '06 340. Both engines fire right up and run solid. After 30 minutes or so, the port engine drops a couple hundred RPM, then a couple more, then shuts down completely. Will turn over, but will not restart. After several hours, fires right back up and runs the same half hour. Has done this four times in a row now. Gauges all show normal, no alarms.

Ideas?
 
Overheat? but there should be an alarm. Do you have smartcraft display that displays alarm or just the beeping type alarm?
 
I wonder if you have a cogged vent line for the port gas tank......after running a while the fuel would get shut off because the clogged vent line would not allow fresh air to replace the gas being sucked out of the tank by the engine...this creates a vacuum in the tank that prevents fuel from flowing out which starves the engine for fuel...after a while with the engine shut down enough fresh air slowly enters the tank through the clogged vent and the cycle starts over again....

good luck....

cliff
 
Will turn over, but will not restart. After several hours, fires right back up and runs the same half hour. Has done this four times in a row now. Gauges all show normal, no alarms.

Maybe one of the fuel pumps - check pressure on the fuel rail?

-Kevin
 
I’d go with fuel starvation as well. Check vents and vent hoses if you can get to them, or just run that motor on an auxiliary tank. Although at cruise your 8.1 will empty a 6 gallon outboard tank pretty quickly lol
 
next time this happens open the cap for the port engine gas filler tube and see if the problem goes away....leaving the filler cap off will allow fresh air to enter the tank the same as the vent line is supposed to do....if this works you have a clogged vent line....

cliff
 
I agree with the fuel starvation idea. If it is starvation, once the suction has built up in the port fuel tank, taking the cap off the filler tube will be more difficult than normal. I had fuel starvation on a brand new car once. Taking the gas cap off was next to impossible. The problem with the car was pinching of the fuel line somewhere. Fixed under warranty, but took the mfg. a long time to find it.
 
I had the same issues. My boat had cool fuel 3 systems and one of the water inlets to "cool" the fuel was clogged. I assume it was causing a vapor lock. Cleaned out inlet and all seems to be good.
 
It was indeed a vent line issue. Thank you all for the input!
 

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