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Old 07-11-2017, 20:32   #1
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Mercury 9.9 won't start for the life of me... what's next?

I have a Mercury 9.9 outboard on my Carib dinghy. I can't start it for the life of me. I changed out the spark plugs and nothing. Fuel is new. I'm lost for words. It's a fairly new engine and it's killing me that it's not working.

Any thoughts? Recommendations? Repair shops that specialized in Mercury engines in New Jersey?

Any help will be truly and greatly appreciated!
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Old 07-11-2017, 21:09   #2
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Re: Mercury 9.9 won't start for the life of me... what's next?

You need fuel, air, compression, spark.
Since you replaced the plug was it wet? To check for spark, remove the plug connect it to the wire and leave it hang on the block. As you pull the cord look for spark on the plug. This is best done early or late in the day, not in the bright sun light. Put you thumb over the spark plug hole pull the cord and feel if there is compression. With each of these, eliminate one before going to the next. Many times the fuel circuit in the carb gets clogged with the fuel evaporating and leaving behind a hard varnish like residue clogging the passages. The idle circuit is very small, it doesn't take much to clog it.
Symptoms for this can be the engine will start with choke on and full throttle but will not idle.
To fix this requires popping off the carb, soaking it in thinner after removing each needle valve, one on the bowl float and probably at least one other in the idle circuit, then after hours soaking, run a thin wire, akin to a guitar string, thru each circuit and nozzle opening in the air tube. A sonic cleaner is great tool for this job if you have access to one.
To remedy this PITA fuel problem, always pull the fuel house off the engine and let it run itself dry each time you are done using it.
Aloha, hope this helps.
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Old 07-11-2017, 21:37   #3
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Re: Mercury 9.9 won't start for the life of me... what's next?

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Originally Posted by Cool Hand Luke View Post
I have a Mercury 9.9 outboard on my Carib dinghy. I can't start it for the life of me. I changed out the spark plugs and nothing. Fuel is new. I'm lost for words. It's a fairly new engine and it's killing me that it's not working.

Any thoughts? Recommendations? Repair shops that specialized in Mercury engines in New Jersey?

Any help will be truly and greatly appreciated!
I take it you have tried both Manual and Electric start

Are you getting a spark from the plug? If so...

Could Be Fuel Pump or Fuel Line issue or Primer Pump valve?

Maybe a blocked injector? Pretty easy to take the carby apart and clean injector - Just make sure you are careful with the gaskets on removal or just buy a new set.

Most service manuals will have schematics of the Carburetor to help you getting it apart and back together - Or Google will help

FYI My only experience comes from taking apart my own Honda Outboard - I'm sure there are many wiser people on this list that can help
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Old 08-11-2017, 06:09   #4
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Re: Mercury 9.9 won't start for the life of me... what's next?

AB808 is right with all of his stuff. I know your pain and have been there. The searching. The blisters on your hand. The frustration. Take a deep breath.
.
.
Ok. My new winter hobby is buying old obs at estate sales snd cl and the like snd fixing them up to run and sell. A great ancillary to Great Lakes sailing; a little chaching and I always have a kicker motor. I am on engine number 11 right now. For what itís worth...

In my experience the main issue that obs that were running and mysteriously stopped face are with fuel supply. The chance of no spark or fouled plugs is usually pretty low. Sailboat motors and dinghy motors donít run so long or often to have it be an issue. Compression issues are for motors that have laid up for decades and have failed gaskets. Plus, it will still start and run for a while, just weakly and improperly. That leaves fuel.

Slowly, and with fresh eyes, recheck each point of your fuel supply. Often the primer bulb is to blame. It goes unnoticed, because the motor will start on whatís left in the carb, activating the fuel pump and hiding the faulty bulb. Remove the fitting where it goes on the motor, and pump some gas right back into the tank to confirm that it is working.
If it takes forever or wonít do it, new bulb and problem is solved.
If it is pumping, reattach to fitting and motor. Pull choke all the way out. Prime til you can feel bulb is full and a lil drop of gas squeezes out of side of motor fitting. Pull start 2-3 times. Then put choke 1/2 in, neutral (of course), full throttle, and give 2-3 pulls. Try it out.
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Old 08-11-2017, 06:20   #5
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Re: Mercury 9.9 won't start for the life of me... what's next?

All good advice, since all of these things go wrong.

First, follow the suggestions re. spark.

Then, so long as it will start with a hard primer bulb, it is not the hose, bulb, or connector. Those cause running problems, not starting problems, because once the bulb is hard and the carb is full, that is enough gas for a few minutes. They may be bad, but come back to those after it starts.

Clogged passages are probably the problem. But before you tear the jets out, simple remove the carb, remove the bowl, and give the bowl, float, float needle, and every opening you can see a good blast. Several times. Use 1/3 can. Then put it together and try.

While it was open, did you notice any corrosion pits or freckles in the bowl? If so, corrosion is the problem. The corrosion particles are clogging the jets. With e-10 gas, it is almost ALWAYS corrosion and very seldom gum these days. Brass and aluminum are a bad pair and e-10 supports corrosion.

The solution is a good anti-corrosion additive (Biobor EB, Merc store & Start) and keeping the vent closes anytime you are not running the motor, even during the day. No moisture, no corrosion, no plugging.

Running the engine dry is just a good way to wear out the fittings. It is not even recommended by the factory anymore, except for extended storage. Because of the reduced fuel volume in the carb, it actually increases gum formation. Better, use the right additive (many are poor, a few are excellent), and keep the vent closed.

(I am on a number of ASTM committees, I drafted the proposed additive standard, and I've tested a lot of them.)
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Old 08-11-2017, 06:29   #6
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Re: Mercury 9.9 won't start for the life of me... what's next?

Besides all the "normal" engine fixes how about the stranger ones:

Is your shut off switch "thingy" in place?

I lost mine and have some leech line holding the switch in the "on" position.

Sometimes I have to retighten the line when the engine won't start
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Old 08-11-2017, 06:52   #7
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Re: Mercury 9.9 won't start for the life of me... what's next?

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Originally Posted by AB808 View Post
The idle circuit is very small, it doesn't take much to clog it.
.
This is the most common problem, particularly with Mercs. I carry a can of starting fluid. A common solution (certainly not recommended by Merc or lawyers) is to remove the throttle lock-out bar so the motor can be started in gear with the carbs rather than the idle channel.
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Old 08-11-2017, 08:17   #8
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Re: Mercury 9.9 won't start for the life of me... what's next?

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Originally Posted by thomm225 View Post
Besides all the "normal" engine fixes how about the stranger ones:

Is your shut off switch "thingy" in place?

I lost mine and have some leech line holding the switch in the "on" position.

Sometimes I have to retighten the line when the engine won't start
What Thomm225 said.... ask me how I know.

It used to be common to see this with motorcycles too. Someone would kill the battery trying to start and then commence to kick. Then some wise guy walks up and turns the Run/Off switch to Run and it's magic.
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Old 08-11-2017, 08:28   #9
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Re: Mercury 9.9 won't start for the life of me... what's next?

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Originally Posted by Cool Hand Luke View Post
I have a Mercury 9.9 outboard on my Carib dinghy. I can't start it for the life of me. I changed out the spark plugs and nothing. Fuel is new. I'm lost for words. It's a fairly new engine and it's killing me that it's not working.

Any thoughts? Recommendations? Repair shops that specialized in Mercury engines in New Jersey?

Any help will be truly and greatly appreciated!

I had a brand new version of this exact engine but the Tohatsu version (2016 Tohatsu 9.8).

It sucked. I sold it two months ago and my arm STILL hurts from pulling the starter over and over and over. I went through two carbs, plugs, fuel filters, ethanol treatments, nothing could get it to consistently work.

I hated that motor, so I sold it. I went electric and couldn't be happier.
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Old 08-11-2017, 08:29   #10
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Re: Mercury 9.9 won't start for the life of me... what's next?

It's almost always fuel. Is the fuel old? did it sit a long time? Remove the carb reservoir and clean it out.
Last time I tried to start my brand new gas home generator, it wouldnt start for anything. Not a pop. It had only been used once. I even drained the reservoir and fresh gas. No go.
I ended up removing the reservoir and cleaning it out. There was a little corrosive buildup inside the reservoir for some reason. After that it started right up.
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Old 08-11-2017, 08:42   #11
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Re: Mercury 9.9 won't start for the life of me... what's next?

The most common problem we see in the repair shop is fuel sitting in carburetor and clogging the jets. Best to run the fuel out, I disconnect the fuel line on my Mercury 9.9 every time Iím finished using it and never have a problem.
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Old 08-11-2017, 08:50   #12
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Re: Mercury 9.9 won't start for the life of me... what's next?

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Originally Posted by Peregrine1983 View Post
I had a brand new version of this exact engine but the Tohatsu version (2016 Tohatsu 9.8).

It sucked. I sold it two months ago and my arm STILL hurts from pulling the starter over and over and over. I went through two carbs, plugs, fuel filters, ethanol treatments, nothing could get it to consistently work.

I hated that motor, so I sold it. I went electric and couldn't be happier.
I have a 2011 Mercury 5 hp 4 stroke extra long shaft outboard as my auxiliary engine.

No problems so far...............and I have yet to change the original spark plug. I have changed the fuel filter one time, and the impeller 3 times.

I do treat the fuel if it will be in the tank(s) over the Winter Months
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Old 08-11-2017, 08:53   #13
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Re: Mercury 9.9 won't start for the life of me... what's next?

So I have had two Merc exhibit the same issue one would not start the other would randomly cutoff. Both were less than two years old. Both had worn out kill switch keys. The little piece of plastic that fits under the red kill button. Grab that red button with your finger tips or a pair of pliers and hold it out while cranking. If that little guy is not fully extended you will get no spark.
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Old 08-11-2017, 09:02   #14
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Re: Mercury 9.9 won't start for the life of me... what's next?

Thanks for all the input, guys!!

I will try all of the above tomorrow morning when I go back to the marina. The engine was sitting on the side for a couple of months while I was sailing from the BVIs to Florida to New Jersey. I think I had it laying on the wrong side (these engines are supposed to lay on the handle, right?) since the handle was on top.

I'll take a look tomorrow and post some photos, too. I really appreciate everyone giving me their two cents on this issue!!
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Old 08-11-2017, 09:07   #15
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Re: Mercury 9.9 won't start for the life of me... what's next?

I feel your pain, man. I received tons of helpful input from folks here back when I was in your position a few months ago:
I hate my dinghy motor

I received lots of the same replies - drain the carb out every time, treat the gas, get new plugs, change your filters, etc. etc.

As I said, I eventually sold mine. I hope one of these fixes works for you. The only thing that worked for me was a carb rebuild or a new carb every couple of months - which I decided was not worth it.
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