mercury 2.5 not starting

bugs

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I seem to be getting fuel. Spark is sparking and smell of vapour from the cylinder when i turn it over with the plug out. stop button seems ok (used a meter). Any ideas? What are the sealed units leading from the stop button and the spark plug (assume timing circuitry?) Might they be the problem. As ever, thanks in advance.
 

snowleopard

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First check to see if it's spark or fuel - take out the plug, connect it to the lead and rest it against the metal of the cylinder block, then pull the cord. If you see a spark the probelm is fuel. If no spark, give the plug a clean up with a wire brush and heat it on a gas ring to burn off any liquid before re-trying.

If it's fuel, check the tank is full, fuel is coming from the tap (disconnect at the carb end).

This engine is prone to the float needle sticking as a result of the mixture in the carb evaporating and leaving just sticky oil. I have to strip the carb on mine tomorrow for exactly that reason. The common symptom is fuel dripping from the front of the engine.
 

bugs

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Thank Snowleopard,
I am getting a spark. I had done as you said with the plug.
I removed the float bowl and fuel seem to flow through the carb ok. I did not remove the float so will check that out this evening.
When I pulled the cord, with the spark plug out, I definitely got a smell of petrol fumes. Is this enough of an indicator of fuel getting through to the cylinder?
 

snowleopard

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if the carb is flooding it won't fire - mixture too rich.

You didn't leave old fuel in over winter did you?

I keep a couple of spare plugs in the tool bag so I can swap them if it doesn't fire quickly.
 

bugs

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Well it had some fuel in over the winter but I have used it about a dozen times since. I've topped up the fuel a couple of times since winter. I had used about half the present fuel in the tank successfully. Usually starts after two-three pulls from cold.
It had started fine a day or two before.
no fuel change made.
 

fireball

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couldn't be a bit of water in the fuel could it?
Sparks ok ...
smells of fuel

Had this problem on the clubs 25hp 4 stroke...
 

snowleopard

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If you lie the motor down after carrying it by the handle, the plug will be at the lowest point in the cylinder and any oil or dampness will drain into it. A plug change should fix that instantly.

Are you getting any fuel dripping from the carb when the petrol tap is open?
 

ShipsWoofy

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I am buying a new plug for my Mercury 2.2 about every 6 months. It seems to work right up to the point it will not fire, then for about 2 weeks it is a b*tch to start. I do not know why I use so many plugs and have after 4 years just started to live with it.

I fit a new plug and it starts on the first pull.

No amount of cleaning of the plug, changing the petrol etc. seems to make any difference. It seems to me that these motors eat plugs.
 

snowleopard

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I wonder if it's the 100:1 mixture that cooks the plugs - the dealer who sold me mine said that the manufacturers didn't design the engines for such low oil ratios, they just pushed the limit to get past the emission regulations and the engines are far happier at 75:1 or even 50:1.
 

pappaecho

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My Suzy 2.2 showed exactly the same symptoms. As it is 5- 6 months old, took it back to the seller, who drained the float bown into a clear container to show me the clear gel like threads which form with aged 2 stoke mixes. Apparently it only occurs with unleaded, the old 4 star did not have the same problems. If you have got old fuel mixed with new it is still likely to be the fuel. I would chuck all into a container and start again, cleaning out all the carb and pipework. I would filter the old fuel and gradually mix it back 1:5 with new fuel mixes, until the old fuel is diluted and burnt away. At 100:1 it is not going to cause any problem at the end of the year if you chuck the remaining 2 stroke into the car fuel tank - dont leave it in the outboard over the winter.
I thought this was an old wives tale until a few weeks ago - I wish I still had my trusty Seagull...
 

cliff

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[ QUOTE ]
I wonder if it's the 100:1 mixture that cooks the plugs - the dealer who sold me mine said that the manufacturers didn't design the engines for such low oil ratios, they just pushed the limit to get past the emission regulations and the engines are far happier at 75:1 or even 50:1.

[/ QUOTE ]I was told the same by a Merc dealer - Stick to 50:1 not 100:1 even though the manual says 100:1 - th eengine was designed for 50:1 but Merc found out it would run at 100:1 for emissions but is knackers the engine quickly.
---------
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“Artificial intelligence is no match for natural stupidity”
Skype id:cliffillupo
 

ShipsWoofy

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Ok lads I will try it at 50:1. If my carb oils up I will send you the bill, well my time pulling the thing to bits anyway.

Seriously, I will give it a go this season and report back if the plugs seem to last longer or not.
 

[2068]

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Despite saying "100:1" on the outside of my Merc 3.3, I've run it at 50:1 for four seasons, and each time one plug has lasted the season. No fouling (unless you run at idle for more than 10 mins). Works a treat...

dv.
 
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