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Old 01 November 2010, 17:52   #1
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mercury 15hp "sneezing"

hi,ive just purchased a late eighties 15hp 2 stroke merc,its been stood for the last 3 yrs so im told,but it has been fogged while its been layed up,ive bought it home and run it in a tank,it sounds sweet,but now and again it coughs and i can only describe as a sneeze with a puff of smoke from the exhaust then its fine again,any ideas?
Andy
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Old 02 November 2010, 02:48   #2
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It could be a missing spark every now and then, but most likely (esp if the motor has stood for a while) is that the carburetor jet is a bit blocked. Easy enough to get the carb off that engine and have a very careful clean and blow through. You could try liquid or aerosol carb cleaner first, unlikely to fix it but sometimes worth a go as it takes half an hour and about a tenner.
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Old 03 November 2010, 07:42   #3
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Quote:
Originally Posted by soley1 View Post
hi,ive just purchased a late eighties 15hp 2 stroke merc,its been stood for the last 3 yrs so im told,but it has been fogged while its been layed up,ive bought it home and run it in a tank,it sounds sweet,but now and again it coughs and i can only describe as a sneeze with a puff of smoke from the exhaust then its fine again,any ideas?
Andy
morning i would suggest that the carb is stripped and clean and the float hight checked,set the mixture screw to one and a half turns out from lightly seated.
if you would like to contact me with any questions but not fridays, my contact details below but please have a serial number as well as there are a lot of diferant 15hp.
uncle al
01869 326411
alan.surman@barrus.co.uk
sneeze= usually running lean
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Old 03 November 2010, 13:11   #4
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Not a mercury but a Johnson 15hp.
My engine kept "sneezing" the fault was a blown gasket. Cost around 3.00 and took around 5 minutes to replace.
Hope this helps !
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Old 03 November 2010, 13:33   #5
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Week idle mixture. If it is adjustable, and it usually was in the eighties, turn the mixture screw on the carb outwards (anticlockwise) a small amount until it runs smoothly. There is a proviso; 2 stroke engines of that era were not particularly refined, often they tended to gas up and run less well the longer they idled, blipping the throttle to clear them was a common necessity.
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Old 03 November 2010, 16:46   #6
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hi,thanks for the replies so far,well ive stripped carb down and blew through jets and passage ways,the only possible issue i have found is the brass tube that runs through carb doesnt sit centrally in the larger brass tube wher the main jet screws in,i assume the of centre tube supplies fuel for the idle jet as it ends up in a seperate chamber where the idle screw passes through,any ideas?
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