Mercury 2.5hp 4-stroke outboard advice

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vseager

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I've just bought a second hand Mercury 2.5 4 stroke outboard for our tender. I believe it's an 07 model but looks like new and has apparently only had about 10 hours use.

Unfortunately I can't get the thing to start. I'm fairly practical and know the basics of engines... enough to do basic servicing etc, but know nothing about outboards.

So far I have done the following...
- Checked oil level (full and clean)
- Read the manual front to back and followed all instructions on starting.
- Drained the fuel tank and filled with new petrol
- Inspected the carburetor (clean)

When I try to crank it, it just seems to have no life, I have tried with the choke in various positions etc. (no idea if that's supposed to help)

I feel I may end up taking it to a dealer to get it working, but thought I would see if anyone on here could give me any pointers first?

Thanks in advance.
 
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Generally it's either fuel or electrics.

The most professional approach would be to remove the spark plug and see if there is a smell of petrol on the plug after cranking. Then hold the plug against the cylinder head and pull the cord and see if there's a spark. Sometimes it's difficult to see the spark so I generally resort to chucking a teaspoon of petrol into the air intake and then see if there is any sign of life. If there is any combustion that narrows it down to the fuel system.

Richard
 
Bav34 said:
+2

Reckon I pulled the starter cord so often I could have moved the tender a couple of miles :disgust:
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:) I think we have all been there! I now stick with oars which use less petrol but require a small amount of porridge each morning to get maximum revs. With a bit of whiskey you can get them to start even on a cold night but it does tend to muck them up in the long term.
 
Thanks for the replies.

I have got the kill cord on, I've also removed the carb and cleaned it out, although it all looked clean anyway.

Tried the petrol on the air intake, that didn't work. I couldn't see a spark from the spark plug, but it wasn't easy to find a good ground as the engine is painted. Is there another way to test that?

I'm reluctant to take it to a mechanic as I'm worried I'll end up spending as much as a new engine by the time they've charged me £50 an hour to look at it.

Any final suggestions?? Or very nice people who happen to know about these in Weat Sussex/Hampshire :rolleyes:
 
No spark = no start. Change the plug first, then the plug lead. It's possible the electronic ignition is broken but unlikely. How does the compression feel when you're pulling? With all that tugging on the chord, the plug ought to be wet. Is it? A wet plug often won't "spark". You need fuel air and the spark to cause ignition. If you know someone with a colour tune plug, you can see it spark and the colour of the flame indicates the mixture. All this is basic petrol engine stuff, anyone with a working knowledge of bikes could help.
 
vseager said:
Tried the petrol on the air intake, that didn't work. I couldn't see a spark from the spark plug, but it wasn't easy to find a good ground as the engine is painted. Is there another way to test that?
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A spark plug tester would be easiest:

http://www.ebay.co.uk/itm/like/1506...f11=ICEP3.0.0&ff12=67&ff13=80&ff14=108&ff19=0

otherwise you could try clamping one end of a battery jumper cable to the body of the spark plug (with the ignition lead still attached), and the other end to a metallic part of the engine.
 
vseager said:
Thanks just ordered a spark plug tester!
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Ordered a spark plug tester? ....... Ordered a spark plug tester? ....Ordered .......
facebook-smiley-in-despair.jpg


Where's the practical boat owner spirit?

Make one!

Lakesailors instructions here: http://www.ybw.com/forums/showthread.php?123723-High-tech-Spark-Tester
 
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Check that the float valve slider isn't corroded and sticking- mine was even though I always ran the engine dry after use
 
OK so I'm getting a spark with the tester.

I tried dipping the spark plug in some petrol and putting it back in the starting, it sounded like it tried to fire but still didn't start.

How new should the fuel be? I think the fuel that was in it when i got it was over a year old, the can I filled it with is probably a month or two old, would filling it with fresh fuel straight from the pump make a difference?
 
vseager said:
OK so I'm getting a spark with the tester.

I tried dipping the spark plug in some petrol and putting it back in the starting, it sounded like it tried to fire but still didn't start.

How new should the fuel be? I think the fuel that was in it when i got it was over a year old, the can I filled it with is probably a month or two old, would filling it with fresh fuel straight from the pump make a difference?
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I'd not expect fuel a month old to cause any problems but ditch all older stuff. You are not entirely sure how old the fuel in your can is so it would be sensible to get some you know to be fresh.

Have you checked that there is a fuel flow to the carb ..... taken the drain screw out to verify that the bowl is filling ?

Tried spraying some petrol into the intake ?

Its a 4 stroke so maybe worth checking the valve gear and the clearances.

Got a compression tester, if so measure the compression. The pros would do this as one of the first checks.
 
The Mercury 2.5 (Tohatsu) suffers from failure of the ignition system; its common, mine did so last year and it was only one year old. The spark gets very weak, it can be seen but it is not regular and too weak when under pressure. If so, it needs a new electronic ignition box.
 
CAPTAIN FANTASTIC said:
The Mercury 2.5 (Tohatsu) suffers from failure of the ignition system; its common, mine did so last year and it was only one year old. The spark gets very weak, it can be seen but it is not regular and too weak when under pressure. If so, it needs a new electronic ignition box.
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That's shocking - oh, and who says 4 strokes are more reliable than the two strokes they replaced! Really that is a terrible failure by the manufacturer if true....
 
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