4 stroke 250hp Yamaha quits while on the water

[golfomex]

Last week after four hours of fishing our 2014, 250hp 4 stroke engine quit and would not start. I disconnected the water separator and connected it directly to the fuel tank. The primer bulb was empty, primed it, the engine ran for about a minute while struggling. Since then the engine will not start. We checked the LP pump and it seems to be pumping correctly, did not check to see if we had any air in the lines. Kind of hard to do when your battling 4-foot waves. Luckily we were rescued, but the engine will not start. We checked the drain plug on the VST but to my surprise the VST had fuel. A mechanic suggested we place a rag full of gas on the air intake to see if it would start but to no avail. I would love to resolve the problem. On my other boat, I have dealt with VST, LP problems, and air in the gas lines, so I am quite aware of how these parts can be a serious problem.

Prior to the engine shutting down. The engine previously had had overheating problems (only at low RPMs). A couple of days prior to our last outing, I changed the impeller, gaskets and the plastic cover. The engine ran fine and did not have any alarms during the whole day until the engine shut down.

I wonder if it is a fuel problem or an electrical problem.

A

[Donnie Coulsting]

Typically if the VST filter is clogged, it will still run at low rpm’s. You said the primmer bulb was empty. Was it flat? This will tell you that there is a restriction between the bulb and the tank. If this was the case the VST should have been empty. The bulb should be firm. Connect the motor to another tank and see if it starts. If not check for spark.

[golfomex]

Thanks for getting back. The engine will not run at all. Yes, the primer bulb was empty and it was not flat. I connected the input line directly from the tank to the bulb. removed the internal gas filter and when I activated the primer bulb, the gas would flow out of filter assembly. So, no flow restriction up to the filter assembly. Checked the spark, seems to be good... Shocked me, so I know it works. Are there any alarm shut-offs that will not allow the engine to run? Such as oil or overheat sensors?

[golfomex]

I also connected 12 Volts to the LP and it pumps, so I believe it's not the LP. I think there is a fuel restriction in the VST. Strange though, it always ran great and never shut off as it did that day.

[Donnie Coulsting]

How did you verify spark? Did you pull a plug or check at the coil? If you pulled a plug, was the plug wet? You can also crank the engine and pull a plug and try to see if you can smell gas. It has to be a fuel or spark issue. I would think if a sensor was tripped it would kill spark but I’m not sure. Only way to tell for sure would be to scan for codes.

[golfomex]

Pulled the plug, did not take out the sparkplug, Will try what you suggested, we are getting a good spark.... If a sensor is tripped, how can you reactivate it???The problem we have is that I am in Florida and the boat is in Mexico at my brother's summer home. The home is in a small community and I don't know where we will get a tech to scan for codes. I will try to get him to take it to a Yamaha dealer. But first, we will try your suggestions. My personal opinion is that it's a HP problem or the VST filter is plugged up. Thanks