8shot 191 Posted June 17, 2011 Report Share Posted June 17, 2011 well a few days ago me and my pals where out fishing all day and the outboard was running sweet untill on the way home ....it started to smoke and then a slight bang...and the engine seized so the back up engine went on and we got back.. when we got home the engine pulled over and started again i run it on a 50.1 mix as it says on the tank...and it was mesured out correctly the bloke i got it off said it was air cooled its a mid 80s johnson 4hp now when i start it it seems to run ok but has a bit of light blue smoke any help please guys Quote Link to post Share on other sites
fat man 4,741 Posted June 17, 2011 Report Share Posted June 17, 2011 Do you use leaded or unleaded petrol,ive got a johnson as well and i find it runs a lot better on ordinary leaded petrol.I also change the plugs every year,it might just have been dirt in the carb that released itself. Quote Link to post Share on other sites
8shot 191 Posted June 17, 2011 Author Report Share Posted June 17, 2011 Do you use leaded or unleaded petrol,ive got a johnson as well and i find it runs a lot better on ordinary leaded petrol.I also change the plugs every year,it might just have been dirt in the carb that released itself. thanks for the reply fat.man i use unleaded in it ... and i cleaned all the jets and carb before taking it out it really needed it aswell as the main jet was blocked i got it of a elderly chap and it must of been stood in his garage for donkeys years regards Quote Link to post Share on other sites
TOPPER 1,809 Posted June 17, 2011 Report Share Posted June 17, 2011 you could have picked a ring up if the engine has stood for a long period it may have had a sticky piston ring and thats picked up pull the head and barrels off it and have a check over the bores Quote Link to post Share on other sites
8shot 191 Posted June 17, 2011 Author Report Share Posted June 17, 2011 cheers mate will give that a go later Quote Link to post Share on other sites
spot 0 Posted September 19, 2011 Report Share Posted September 19, 2011 (edited) 1980s Johnson 4hps aren't air cooled.they have a water pump housing and impeller in the in the gear case.The bad thing is they don't have a tell tale that lets you know if the pumps working. Sounds like you over heated and seized then un seized when you cooled down. A new impeller should sort you out Edited September 19, 2011 by spot Quote Link to post Share on other sites
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