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Old 21 August 2013, 04:07   #1
Country: UK - England
Town: Gloucestershire
Boat name: Osprey
Make: Osprey Vipermax
Length: 5m +
Engine: E-tec 300 G2
Join Date: Dec 2006
Posts: 4,015
Mariner 90 2 stroke smoking and rough at lower revs

A friend has a circa '96 engine on the back of a Humber...

When at idle it smokes quite heavily and sounds very lumpy at low revs (even for a 2 stroke)

Am going to try new plugs first and see if this helps, however any other tips...?

Chris Stevens

Born fiddler
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Old 21 August 2013, 04:43   #2
Country: UK - England
Town: Northampton
Make: RibTec
Length: 5m +
Engine: Outbaord mariner 75
Join Date: Apr 2011
Posts: 506
check the carb settings.
mine smokes a lot after ideling for some time.
you can also check the oil is ok. try to use good oil tcw3 ( quicksilver ah-hem lol )
any vids or pics to show it.
there is also an adjustment on the carb to oil pump but be very very careful if your changing that

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Old 21 August 2013, 04:54   #3
colcreate's Avatar
Country: UK - England
Town: Cheshire
Boat name: Gollione
Make: Avon Searider 5.4
Length: 5m +
Engine: 90hp
Join Date: Jun 2010
Posts: 347
Is he premixing fuel/oil or using oil injection?
If its running lumpy and compression is good/equal on all cylinders then carbs are probably out of balance. Would recommend stripping them down and cleaning them, examining for spindle and float valve wear and a general tidy up. Check linkages are good and adjust/balance according to manual. Did this on mine and it is much improved, plus piece of mind that all is well and unlikely to seize due to a gummed up carb.
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Old 21 August 2013, 10:38   #4
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 913
does it just run lummpy on tickover when trimmed in as far as it will tuck under? If so trim it in so that it is straight up and down is it still lummpy?If so how old is the fuel?take out the sparkplugs and DONT wipe them are they all the same colour? if one is a differant colourput it into one of the other cylinders has the colour changed?If it has check idle air screw (mixture screw) it should be one and a half turns out from lightly seated on all three carbs,the book said a differant setting
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