2004 Mercury 115 FOURSTROKE Power Loss - Moderated Discussion Areas

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Author Topic:   2004 Mercury 115 FOURSTROKE Power Loss

JEdmunds posted 07-04-2014 11:44 AM ET (US)
I'm having trouble giving my [2004 Mercury 115-HP FourStroke outboard engine an open] throttle after a period of idling. The [2004 Mercury 115-HP FourStroke outboard] engine appears to idle fine. My first trip out this year, [the boat] could not get up on a plane at all. [The engine] seemed to be bogging down and having trouble getting fuel. I replaced the spark plugs, in-line fuel filter and the engine-mounted fuel filter. The engine mounted fuel filter had a lot of popcorn-kernel-looking debris, which turned out to be coming from an 8-inch piece of gray fuel line next to the primer bulb; I replaced the fuel line. I also put some SeaFoam in the boat fuel tank.
The engine is running much better, however, if idling for a few minutes, the engine still bogs down on throttle-up. When I turn the engine off and back on, I'm able to take off right away with full speed, and the engine runs fine. I'm baffled.
jimh posted 07-04-2014 12:45 PM ET (US)
That gray jacket Mercury fuel hose is notoriously bad. It probably was causing significant fuel restriction.
Your spark plugs may be loading up with fuel residue at idle. Also, since you are running a fuel additive (Seafoam), your engine will probably be letting loose a lot of combustion deposits. They'll tend to foul the spark plugs. Check the plugs after you run the Seafoam-doped fuel, as they might need some cleaning.
JEdmunds posted 07-13-2014 10:24 PM ET (US)
I removed the intake manifold to access the fuel injection pump. Fine particles of the fuel line had made it through the engine mounted fuel filter into the fuel injector pump bowl and had clogged up the filter of the fuel injector pump. I cleaned up the filter and reassembled the pump and intake. I tried cleaning the fuel injectors; but, I don't believe I accomplished much. Back in the water... the engine seemed to run fine. I think I'll take the injectors to a professional just to make sure they are spraying properly.
sosmerc posted 07-23-2014 12:48 AM ET (US)
You are wise to have your injectors flow tested and cleaned.
Injectors need routine service just like carbs, especially with today's fuel blends. Running ethanol free fuel will help, as well as annual replacement of ALL fuel filters in the system.

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Author	Topic: 2004 Mercury 115 FOURSTROKE Power Loss
JEdmunds	posted 07-04-2014 11:44 AM ET (US) I'm having trouble giving my [2004 Mercury 115-HP FourStroke outboard engine an open] throttle after a period of idling. The [2004 Mercury 115-HP FourStroke outboard] engine appears to idle fine. My first trip out this year, [the boat] could not get up on a plane at all. [The engine] seemed to be bogging down and having trouble getting fuel. I replaced the spark plugs, in-line fuel filter and the engine-mounted fuel filter. The engine mounted fuel filter had a lot of popcorn-kernel-looking debris, which turned out to be coming from an 8-inch piece of gray fuel line next to the primer bulb; I replaced the fuel line. I also put some SeaFoam in the boat fuel tank. The engine is running much better, however, if idling for a few minutes, the engine still bogs down on throttle-up. When I turn the engine off and back on, I'm able to take off right away with full speed, and the engine runs fine. I'm baffled.
jimh	posted 07-04-2014 12:45 PM ET (US) That gray jacket Mercury fuel hose is notoriously bad. It probably was causing significant fuel restriction. Your spark plugs may be loading up with fuel residue at idle. Also, since you are running a fuel additive (Seafoam), your engine will probably be letting loose a lot of combustion deposits. They'll tend to foul the spark plugs. Check the plugs after you run the Seafoam-doped fuel, as they might need some cleaning.
JEdmunds	posted 07-13-2014 10:24 PM ET (US) I removed the intake manifold to access the fuel injection pump. Fine particles of the fuel line had made it through the engine mounted fuel filter into the fuel injector pump bowl and had clogged up the filter of the fuel injector pump. I cleaned up the filter and reassembled the pump and intake. I tried cleaning the fuel injectors; but, I don't believe I accomplished much. Back in the water... the engine seemed to run fine. I think I'll take the injectors to a professional just to make sure they are spraying properly.
sosmerc	posted 07-23-2014 12:48 AM ET (US) You are wise to have your injectors flow tested and cleaned. Injectors need routine service just like carbs, especially with today's fuel blends. Running ethanol free fuel will help, as well as annual replacement of ALL fuel filters in the system.