Cough, sputter, no acceleration.

[Jetter]

Hi Everyone. Being a complete noob I am looking for any guidance I can get. I have an 08 Z1. Marine power 5.7l 360hp motor.

Have had boat out 4 times. Yesterday it ran fine then after sitting on shore for a bit, went out and when I tried to accelerate it coughed and bogged a tiny bit then picked up and went. Ran fine again out in water for an hour. Back to rest on shore then out to put it away and this time it accelerated for a bit before it started to cough and sputter and just would not go. Tried neutral and revving engine and same cough sputter - no power. But it kept idling. Turned off and on - same deal. Now I'm starting to panic and thinking I'm gonna need a tow in. Opened both lockers to let engine get some air and fire it back up. Back to life - closed the covers and it ran perfectly fine back to launch.

Besides the obvious above - just wondering what is normal operating temp? I seem to run high 150's into the 160's. Is this too high?

My first plans are to change impeller and fuel filter (if I can find it). Don't know if original owner ever changed impeller.

Any other thoughts would be greatly appreciated!

[Z1Fan]

Temp is right dead on, if not a little low, it all depends on the thermostat

[ajnesbitt]

Could be vapor lock.

[Jetter]

That is exactly what previous owner just emailed me not 5 minutes ago. What is vapor lock exactly and is it preventable?

[ericinmich]

Do some googling on vapor lock. Basically the fuel in the line "boils" and now you have a vapor in the lines and no fuel to inject. Fuel (or a fluid) boils at a lower temperature under lower pressure. When you shut off the engine the fuel pressure to the injectors bleeds down and then the heat soaking up from the engine causes the fuel to boil.

It's been around since carberators. First thing to try is to never turn off the engine after running hard. Also, while running before shutting it down (at idle or fast idle) be sure the blower is on, and leave it on while the engine is off. You could even open the hatch up to let things cool down while engine is off.

Ideally, the pressure stays high in the fuel lines to the in injectors but fixing that could be tough. Injectors get dirty and leak when off. Fuel return regulator (if there is one) gets leaky...

I'd try to be sure it cooled down first.

[Jetter]

Do some googling on vapor lock. Basically the fuel in the line "boils" and now you have a vapor in the lines and no fuel to inject. Fuel (or a fluid) boils at a lower temperature under lower pressure. When you shut off the engine the fuel pressure to the injectors bleeds down and then the heat soaking up from the engine causes the fuel to boil.

It's been around since carberators. First thing to try is to never turn off the engine after running hard. Also, while running before shutting it down (at idle or fast idle) be sure the blower is on, and leave it on while the engine is off. You could even open the hatch up to let things cool down while engine is off.

Ideally, the pressure stays high in the fuel lines to the in injectors but fixing that could be tough. Injectors get dirty and leak when off. Fuel return regulator (if there is one) gets leaky...

I'd try to be sure it cooled down first.

Thanks for the great explanation. It was warm yesterday up here in Alberta (90s). I did come to shore and shut it right off. Now I know to let it idle with the lockers open for a bit. I leave my blower on for basically the whole day when I'm out.

Thanks again!

[scoot18]

Well its definitely not an impeller issue, that wouldn't create that symtom. It is either a fuel starvation issue or possible ignition breakdown. My 1st thought when reading your post was a partially clogged fuel filter or trash, water etc in the fuel. Or a weak ignition spark, from possible dist cap or rotor, but if that was the issue it would probably be more constant and not so intermittent. I would check, replace fuel filter and inspect fuel once the cannister is removed first.

[ericinmich]

I spent 30 yrs in engine controls, fighting vapor lock was a huge problem especially in the early days. The hardest test was to run the vehicle hard (at desert test facility) and then park it in a wind break so no airflow would occur in the engine compartment. All vehicles now have some sort of fan run on to help keep air moving. Letting the engine idle (fast idle better as more water flow) helps a ton. Going to higher pressure fuel systems that don't bleed down essentially fixed the issue... as long as they don't bleed down. Some engines (including boats) have fuel line coolers to help the situation. My folks boat as a kid had a carb, it had vapor lock issues (fuel in the bowl would boil), and a nice cool down was it's fix.