Wife ain't happy - outboard has turned flaky

[Kenpimentel]

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

[weavis]

simplest things first.
Fresh fuel.

[Vasco]

Well my first thought was, seeing you're in the Bahamas, dump the Mercury and buy a Yamaha 2 stroke. But, if you don't want to do that, have another go at the carburetor. Clean the jets again and again.

[ontherocks83]

Start with fresh fuel as it is the most likely culprit and is a cheap fix if it is the problem. My assumption is if the fuel is that old and you didn't treat it with stabil then the fuel passages in the carb are gummed up. It doesn't take much.

Best case is you get fresh gas, put in stabil and a carb cleaner then proceed to run the hell out of it and it may clear itself up.

Worst case (if the problem is bad fuel) is running it hard doesn't fix it then you have to disassemble the carb and really get in to every jet and orifice. (Only use carb cleaner to clean jets and orifices in the carb. Never stick a pipe cleaner or anything in those holes. Some of them are metered down to ten thousandths of an inch and scoring one can cause problems)

If those dont fix it, it could be a mixture or idle setting is off. If your idle mixture screw is set wrong it can cause all kinds of problems. You would need to find the manual for the presetting and then fine tune it from there.

[motaman9]

Doesn't white smoke normally mean water in your fuel?


Sailing somewhere.....

[Kenpimentel]

Thanks for the many replies.

- It must be fuel-smoke because it smells like fuel-smoke - it isn't water-smoke
- I will try new fuel as soon as it stops raining here in Wash DC (for the summer)
- The fuel wasn't allowed to sit in the outboard for nine months, it was sitting in my big portable tank. The outboard was running relatively OK a month ago, after I stripped/cleaned carb due to a 2 month lay-up - and running the same old fuel. My recent problem is more like 2 weeks old.
- I found a new carb for $90, so I'm considering that option after I try the new fuel and once again, try to strip/clean the carb.

[a64pilot]

Originally Posted by motaman9

Doesn't white smoke normally mean water in your fuel?


Sailing somewhere.....

It can if it's steam then certainly, but it can also mean stupidly rich mixture too, that would also account for the sheen on the water

[a64pilot]

You need carb soak to clean a carb, often the spray can stuff just doesn't get everywhere, and it's no where near as powerful a solvent as the soak stuff.
I've even had to resort to an ultrasonic cleaner to get one of these little carbs completely clean.
Once you get it right, by most likely buying the new carb, always from then on use Sta-bil, I mix it at twice recommended strength (does no harm says so right on the bottle) but I have no issues, knock wood.

[ontherocks83]

Originally Posted by a64pilot

It can if it's steam then certainly, but it can also mean stupidly rich mixture too, that would also account for the sheen on the water

absolutely true,

but if it only likes to run with the choke on that means it is running lean and closing the choke restricts the amount of air which brings the fuel ratio back down to normal. So if it is lean then it is either from a blockage (gummed up fuel in carb) or from idle settings being wrong.

[MarkSF]

Originally Posted by Kenpimentel

Thanks for the many replies.

- It must be fuel-smoke because it smells like fuel-smoke - it isn't water-smoke
- I will try new fuel as soon as it stops raining here in Wash DC (for the summer)
- The fuel wasn't allowed to sit in the outboard for nine months, it was sitting in my big portable tank. The outboard was running relatively OK a month ago, after I stripped/cleaned carb due to a 2 month lay-up - and running the same old fuel. My recent problem is more like 2 weeks old.
- I found a new carb for $90, so I'm considering that option after I try the new fuel and once again, try to strip/clean the carb.

Water smoke, is that the new name for steam?

Seriously, though, I couldn't see any mention of always running the carb dry after use, which is the single most important practice for keeping any ob running well.

[rolandcavanagh]

Sounds to me like a restriction in the fuel supply - a collapsed hose, plugged filter, tank vent not open - something causing inadequate fuel flow. Fiddling the choke to make it run is a common symptom of this.

Good luck, and please let us know what you find.




Sent from my iPad using Cruisers Sailing Forum

[Kenpimentel]

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

[Vasco]

Originally Posted by Kenpimentel

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

Get the new carb for $90 and soak the old one and keep it as a spare or sell it in the Bahamas. Last season a cruiser was screwed as he needed a new carb for his 4 stroke and they were nowhere to be found in the Bahamas, and this was a Yamaha which is a popular brand there but unfortunately very few 4 strokes.

[irwin37]

Sounds like blown head gasket to me. Good luck keep us advised.

[Kenpimentel]

Are there definitive signs of a blown head gasket I could look for - without removing the head?

There is no water in the oil.

When I removed my old spark plugs, they were black at the tips from poor fuel mixture (I assume). I did not see any sign of water at that point.