Outboard Problems -- Any idea what this sound indicates?

[Charlie H]

Hi folks,

Another season, another round of outboard problems! Wonder if you wouldn't mind having a listen to this:

https://www.youtube.com/watch?v=_mIdrfs ... e=youtu.be

Having done some research, I am concerned this sound indicates a detonation/pre-ignition problem. Can anyone confirm this?

I had the outboard serviced this year and the mechanic said it ran fine in his tank. When it went back onto the boat (with my fuel system), it idled roughly and started in with what, to my ear, sound like "knocking" or "pinging" sounds.

I've now installed a new fuel assembly and fuel line, along with fresh fuel. Starts and idles fine now, but still getting this sound periodically when the throttle is in the "starting" position. It idles at low revs fine.

Any thoughts would be appreciated.

Many thanks,
Charlie

 

[NewportNewsMike]

Hi Charlie -

I am certainly no expert outboard mechanic, although I have messed with small engines and outboards for 50 years now, mainly just fixing problems in my own "stable" of lawn equipment and boats. So, keep that in mind - my thoughts may be worth exactly what you have paid for them!

I would not call that detonation / pre-igntion, per se. In my experience is that when cars and outboards have this condition (often called "pinging") due to improper timing (too advanced), or lack of gasoline octane for the load, they have NOT momentarily stopped running the way your outboard does. They keep running along, but are making the "pinging" sound as they run. And usually the problem occurs under load, not at idle.

That momentary stopping and then "catching up" again would have me looking at my ignition system pieces and parts. A new plug for sure, and if that was not a problem, the ignition coil (power pack in outboard-speak) would be my next item to make sure it was up to snuff. Needless to say, I would take a close look at the spark plug wires also. Try looking at the motor running at night with the cover removed to see if there is any stray "sparking" going on where it should not be. With all that said, I would think that any ignition problem at idle would also show up at other RPM levels as well.

Another thought: Since it had old fuel in it, maybe some of it deposited some "varnish" in the narrow passage ways of the carb. If it runs fine at mid and upper RPM levels, but not at idle, I would look at the idle circuit "passages" in the carb to see if they need cleaning. Outboard motor carbs use different "passages" in the carb for the different RPM levels. You may be able to do some carb cleaning by spraying carb cleaner into the carb when the motor is running at idle.

Another indication to me that it may be fuel or fuel delivery system related, is that I always pull the hose and let the engine use all the "stored" gas in the carb bowl whenever I am finished using the motor. The sound and shake it makes just as it runs the last drop or two of gas through the engine is similar to what your engine is doing.

If it does turn out to be fuel related, I have some tips for you. I can't say they will prevent all your motor problems, but over the years, they have kept mine to a minimum. I always use mid-grade brand name (Shell, Sunoco, et cetera) gasoline. I always use a fuel stabilizer like StaBil in every tank (not just for storage, but every tank full). I always run the carb bowl dry when I am finished using the motor. Am I spending extra money to do all this? Yes, I am. But not having any gasoline-related problems is worth something, so I am happy with the system.

Hope you get it sorted out quickly - motor problems are irritating! Let us know what it was.

 

[Curt]

Charlie,

I am no mechanic either but can relate to problems that happen on board and not in the test tank. Fuel delivery was my problem. First was a bad fitting on the motor end, air was let in and the motor stalled, the greater demand for fuel the more often it quit. New fitting, problem solved. The very next year the motor would start easily every time and then sputter and stall. Off to the shop where it ran just fine. I replaced the gas, it was stabilized but from the previous season. New fuel, starts right up, sputters and stalls. Back to the shop and no problems with the motor.

The problem was the fuel line was so old it was stiff and the primer bulb deteriorated. I was told the "new" E-10 is as harsh on the fuel lines as it is on seals. So new gas line with correct fittings and no more problems. Not saying that is your problem but it is something to check out.

Now that I publicly stated no more problems I am most likely screwed.

 

[NewportNewsMike]

I gave given it some more thought and have some more thoughts that may put you on the path to solving it.

To have continued smooth running, you need four things, all at the appropriate time: compression, fuel, air, and spark. To me it sounds as if you are losing one of those four, but only momentarily. Almost immediately upon lose, whatever is missing, returns. Lets look at each in turn.

Compression: You lose compression by having bad rings or a valve problem. It does not make sense that you would have an intermittent ring problem, so lets eliminate that. You could have a valve that sticks every now and then. But your motor seems to clear itself up pretty quickly, so probably not a sticky valve. So lets eliminate compression as the problem.

AIr: The motor needs a constant supply of air to continue running. But the air supply is not going to come and go fast enough to give you the problem you're seeing. So, lets eliminate air supply as the problem.

That leaves us with either fuel or spark as the source of the problem.

Fuel: As I said in previous post, your motor does make the same noise and shake that mine does as it (intentionally) runs out of gas at the end of each use. If that is the case here, it would have to be something that happens, and then almost immediately "fixes" itself. Fuel is delivered to carb bowl and then used in carb passages / jets. Maybe a sticky bowl float? Not sure it would "fix" itself so quickly. Trash in the bowl clogging the needle valve from time to time? Maybe - it does happen. Ditto with trash or varnish clogging a jet or passage way. But I do not think that a fuel related problem would repeatedly, momentarily occur and then fix itself.

That leaves use with Spark: Ignition systems do cut out or skip, but usually under load, not at idle. Could have a bad / loose plug wire, but again usually shows up under load, not idle. Could be a loose connection some where on the primary (low voltage) side of the circuitry: the rotating flywheel has to provide the signal to the coil to get it to supply high voltage to the spark plug to create spark.

Hopefully, this has given you some ideas on how to proceed.

Keep us posted on your success!

 

[HERSH]

I cannot open the u-tube link. But on all my small motors I use HIGH TEST gasoline.
I would try that first -- .


Hershey

 

[NewportNewsMike]

I cannot open the u-tube link.

Me either at first until I played with it.

I ended up copying the link and pasting in a new "address bar".

 

[Charlie H]

Thanks for the suggestions, guys, much appreciated. I am reading them carefully and I will be sure to post an update.

Cheers, Charlie

 

[Charlie H]

Just wanted to post an update. There is a mechanic at the marina where I keep my boat, so I asked him to have a look at the outboard as my research and experiments suggested that it was a carburetor problem beyond my skill repair. After replacement of the spark plug AND a cleaning and overhaul of the carb, I'm told the outboard is running beautifully. Looking forward to confirming this myself and finally getting out on the water!

Thanks again for the suggestions, especially to NewportNewsMike - your analysis of the problem was very insightful.

Cheers, Charlie

 

[Rightbrainer]

Hi Charlie-
Glad you got your outboard running right. When an engine sneezes like that, it indicates that the idle is running lean. That is consistent with a clog in the idle circuit in your carburetor. New spark plugs are always a good idea. Thumbs up for your mechanic. Marty