Mercury 10hp XR

flyingskipper

flyingskipper

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I have a problem with my 2 stroke 10hp outboard. It starts first time everytime and runs up to half throttle very well. But as i increase the speed to full throttle it starts to loose power and missfires. I have renewed the coils, new spark plugs and cleaned the carb. Anyone had the same problem or could someone shed some light on this.
Thanks.
 
If its a carb engine, it could be fuel stravation - clean the main jet and needle jet out and make sure there is no crud in the float chamber. Also, check the float, its jet and its level. But firstly make sure the airfilter (if there is one) is clean. Stray sparks test - someone has already mentioned. Anothe thing is that the the fuel tank vent is breathing properly - normally through the filler cap. Its something simple.... I just know it!!
 
[ QUOTE ]
If its a carb engine, it could be fuel stravation - clean the main jet and needle jet out and make sure there is no crud in the float chamber. Also, check the float, its jet and its level. But firstly make sure the airfilter (if there is one) is clean. Stray sparks test - someone has already mentioned. Anothe thing is that the the fuel tank vent is breathing properly - normally through the filler cap. Its something simple.... I just know it!!

[/ QUOTE ]

He's cleaned the carb's!!!!!!!!!!
 
You dont give the age

You mentioned coils is it old enough to have points (and condenser)

Check the ignition system as suggested. Check the spark at each plug, using a spark tester if posible, even an improvised one.

The pros will suggest a compression test!

How well have you cleaned the carb? Sometimes difficult to get the jets clean without poking a soft wire through them.

Will it run better with a bit of choke. If it does then clean the carb again esp the high speed jet.

Is the float level correct?

Possibly a fuel supply problem. Tank vent is already mentioned.

Fuel filter?

Air being sucked into the system ... the fuel line connector is a suspect there.

Fuel pump? Try pumping the priming bulb if that gets it going properly then it is one of these things.

If all else fails go to the Mercury board on the iBoats forums but if you do give the full model particulars preferably in the text.

In the meantime stick with the Seagull in your avatar!
 
I had the same fault with my XR, just a smallest piece of debris in the main jet caused it to do this.

Clean it through and it should be fine. Of course, I'm assuming you've checked the basics, might be worth changing plugs too.
 
Hi I have just got it in the workshop and i have just done a compression check and its giving me 60 lbs/2inch on each cylinder is this about right do you know. Im am also going to stip the carb right down to cleanit i will keep you posted. Thanks for all the info, all is well needed.
Cheers.
 
I think 60 psi is a bit low, but i'm no expert, Provided they are pretty much the same on each cylinder and it starts easily enough I'd not worry.
 
Would you believe it:
After cleaning the carb etc i looked under the fly wheel to see if there where any ignition points - no points found, but what i did find is one of the magnets on the rotor had broken into three pieces. None are now available but found someone to manufacture them for me at a good price.
 
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