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It's a 2006, 40 hp, 4 stroke merc on my 13 sport. No problem starting, turn key and it fires first time. Runs at idle speed without difficulty but when accelerating, it only obtains 3000 RPM and runs rough. Seems it is bogging down, runs rough, and is unable to achieve higher RPMs and plane. After 15 minutes of running in this bogged down state, it sputters and then takes off like a rabbit. The rest of the day is great, runs like the day I bought it. I had it winterized last fall, when to SW Asia (courtesy of the AF) and returned this summer to enjoy boating. This has occurred each time (3) I have been out in the last 2 months. I use fuel stabilizer, keep the tank full, and checked all engine wirings/connectors. My gut tells me it's a clogged fuel injector that clears itself. Any ideas on what I can do to correct this issue? Thanks for the suggestions.

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Get a 3 gallon tank, and run an entire can of seafoam in the gas. I would start up the boat on the 3 gallon tank and let it run a bit to get the seafoam throughout the entire fulesystem. Then shut her down and let sit overnight. Next day, start her up, and go boating.

I did bascially the same on my tractor that was giving me fits and it worked great.

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I had similar issues with my Johnson 50 hp (except, it didn't take off after 15 mins of running rough). It was the "thermostat", when it sputters and run's rough, see if you can hold your finger on the head near the spark plug, you should be able to keep your finger there for a 1-2-3 second count before it get's too hot and you need to remove it, anything less than a "1-2-3" second count, and she's runnin too hot. Mine was running "Hot" enough to kick it into "Slow mode" (drop's 1 cylinder, and limits the revs to about 2000 rpm) but, not hot enough to set off the "overheat" alarm. Just a thought.

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Kamie, thanks for the tip on SeaFoam, I've read much about this on the forum. Cheap fix/preventive measure that I will definitely use. MW, you bring to mind an item I noted yesterday. The engine housing/lid felt a bit warm to the touch yesterday, almost too warm for the amount of sunlight the black lid should be and what I remember in previous outings. Of note, water pump is working fine. Is the thermostat an item that is easy to change by a novice?

Thanks

Zepada

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I'm not familiar with the "Merc", my old 1987 OMC 48 spl was pain to get to the stat, my newer "2004" Johnson was easy, see if you are "Runnin Hot" first.

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Kamie and MW,

The fuel line was broken down by the alcohol/water mixture. The Seafoam helped but not 100% and the thermostat was working fine. I then removed the fuel line and attempted to blow air under pressure through it and found it was partially obstructed. I cut the line in a number of places and found the inside to be goo. What are others using as a fuel stabilizer when using the 10% alcohol blend?

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Are you referring to the fuel line on the motor or the fuel line from the tank to the motor.........I assume mean the ones on the motor............I would go to a marine store and get good quality hose that is the same as you have now. You could get line from an auto parts house, but think you would be better off to spend a little more and get the marine grade if possible