My wife will shoot me if I don't fix the outboard

We have a 4-stroke Mercury 15HP 2008 outboard. When it runs properly, it will idle fine at low revs. It works just like we want it to. Right now, it is the engine from hell. Here are the symptoms:

- starting with cold engine:
- ambient temp: 60F
- start with choke out on 1st or second try
- exhaust is smoky white - assume it is unburned fuel
- I play with the choke, the cloud is less, but, engine won't stay running unless it is fully out
- With the choke fully out, put it in gear and get underway, engine is running poorly/uderpowered, so I push choke in a little
- Engine speeds up to expected power output, this lasts for about 2 minutes, then if I don't do anything, the engine will slow and die, putting the choke back in, gets it to run again, but poorly
- If I throttle up, everything seems to run as expected with choke in, no dying
- After 5-10m of running, the engine will barely idle with choke in. It runs very rough and will eventually die. Choke out will generally keep it from dying, but it runs rough
- I notice signs of fuel/oil? in the exhaust water, I don't remember ever seeing this before. This seems new. I think 4-strokes are not supposed to do this?

What I've done:
- I mounted a spin fuel filter on transom of dinghy and the fuel goes through that before going to outboard
- I only use non Ethanol fuel (it was a nightmare when I didn't)
- I replaced my fuel lines last year (because of the Ethanol destroying them)
- Thinking I over-filled the oil in the crankcase, so I removed oil until it is barely just 1/2 on dipstick, hasn't seemed to make a difference
- Replaced the spark plugs
- Removed the carburator and cleaned with carb cleaner - didn't see any junk in bowl
- Replaced the bowl gasket
- Checked the jets that I could check, they all seemed to be working

What I haven't done:
- The fuel is about 9 months old, I'm assuming it is OK, but I haven't tried with fresh fuel

What it means is that we can barely use our dinghy. At odd times, it stalls - generally when you don't want it to. My wife ain't happy about the situation - she's put me on notice.

Any help would be appreciated.
thanks,
ken

If it runs better when choking it, you have a fuel problem. I would pull the carbs and have them gone through again by someone who knows what they are looking for, you missed something.

In the past, when I had all the ethanol-related problems, stripping the carbs and cleaning them did fix the problem I was having. But, I think you're right. There is something wrong even though it seems clean and the jets seem to work.

Is there any chance this could be an exhaust valve or valve issues? They've never been adjusted that I know of.

Update:
- I bypassed my spin filter and stuck the gas hose directly into a fresh tank of gas
- I let it run for 15 minutes, so it should be full of new fuel
- I still see signs of fuel skim on water
- While the engine will now barely idle with the choke in and fuel throttle at idle, increasing throttle does not necessarily give me instant throttle up, instead it balks
- Continuous white smoke/steam, though less

I have to believe the problem is either:
- carb jets or settings aren't right
- exhaust valves sticking? Read that on another forum, but not sure it is something I can adjust without proper tools

kenpimentel said:

- Continuous white smoke/steam, though less

Click to expand...

If it were a car I would have said blown head gasket.'Cause it sounds like water mixing with oil in the cyl

I'm now trying to acquire the tools to run a compression test to verify.