2007 Mercury 115 4 Stroke been sitting a few years

I got a 2008 Pontoon from my ailing uncle. It has been sitting for several years. It has a 2007 Mercury 115 4 Stroke. We replaced the fuel lines, fuel, impellar and oil; that got her to start up but she wont idle. I can run her at around 1200 rpm but she runs rough and is smoking bad. I am at a loss, any ideas?

compression test, Open air gap spark test,fuel diagnostics, In that order, Was fuel tank flushed? Moore than likely entire fuel system is contaminated!!

johnnygjr said:

compression test, Open air gap spark test,fuel diagnostics, In that order, Was fuel tank flushed? Moore than likely entire fuel system is contaminated!!

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Yes, we drained the fuel tank and put fresh gas in.

Was the inside of tank cleaned and inspected for contamination

Carbs probably need to be pulled and cleaned. Mine is a 2005 and ethanol broke down the linings of the fuel lines and the fuel pump and carbs were full of debris from it. Rebuilt the fuel pump and cleaned the carbs and she ran like new.

johnnygjr said:

Was the inside of tank cleaned and inspected for contamination

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We drained all the old fuel out but didn't clean the inside of the tank.

snathanb said:

Carbs probably need to be pulled and cleaned. Mine is a 2005 and ethanol broke down the linings of the fuel lines and the fuel pump and carbs were full of debris from it. Rebuilt the fuel pump and cleaned the carbs and she ran like new.

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This one is an EFI but I bet the same thing applies.

We got movement on this. Did all the testing suggested and everything tested out fine.

Here is the interesting part, we disconnected the fuel line so we could run all the gas out for the spark/compression tests. It ran fine for several minutes, ran perfect actually.

When we hooked the fuel line back up it started flooding out the top 2 cylinders and only firing on the bottom 2 and running like in the video. While it was running like that we disconnected the fuel line and within 20 seconds it started running perfect again.

Is this a fuel pump problem? Could those 2 injectors be stuck open? Very baffling but was nice to see her idling perfectly!

I might have found the culprit, in the FSM there is a vacuum hose (circled in red) that I read many posts saying that it would get a crack in it and since it is submersed in gas it would start sucking gas into the crankcase. When we unplugged the fuel line, the pump shut off and the vacuum shut off. When I got in there the hose was completely gone. All that was left was the hose clamps! I also found out Mercury changed the hose from a rubber compound to a teflon (they don't admit it was a problem, but I imagine this would be why). Ordering a new hose, I will update when I get it all back together and change the oil (AGAIN)!