I have a 1985 Suzuki, 85 hp 2 stroke out board, that misfires at low rpm, i.e when coming up the Hamble @ 6 knots, very irritating. just a bit more throttle and shes fine, but the boat is on the plane. I have changed plugs and leads etc still does it! what do i check next and how please????
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I know shes old, but you gotta start somewhere!!
check the coils with an Avo to eliminate them from the problem, then think about the carbs and reed valves. Yamahas have a habbit of sneezing at slow speeds if the reeds gum up with old fuel oil deposits which mean they don't close properly. The carbs could also be gummed up. Petrol and oil turns to a gum like substance over a length of time then sets hard like varnish. It could just need a good strip of the carbs and blow through with compressed air. For a fiver you could try a can of carb cleaner first squirted in the engine whilst its running.
That is the nature of the beast - another cause is too much oil - remember the amount of oil needed at 6,000rpm bit different to whats needed at tickover.
Thanks for your thoughts chaps, will check the coils and run some carb cleaner through, with regard to over oiling, the motor is oil injection/auto oiling, so would'nt want to tinker with that
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I know shes old, but you gotta start somewhere!!
Mark, no don't fiddle with the oil injection. If the pump is anything like the Yamaha ones there is a bleed screw incase air is allowed in the pump but otherwise leave well alone. As a side issue I am led to beleive by those in the trade that early Suzuki's ran a very lean mixture and there is no harm in adding 1:100 mix in the fuel just to be sure or after a long lay up. Only Suzukis' though.
