Montgomery Ward Seaking 7.5 HP Clinton engine slow idle back fire

[jhnyutah]

I received a Montgomery Ward Seaking 7.5 HP outboard with a Clinton engine model # K750 3107 D. It hasn't been started in a long time. I mixed some 40 to 1 and fired her up. She runs great, very clean and very strong. When I go to slow idle she back fires and then dies. I can see the fire. Can someone tell me how to fine tune her. I am running her between 2000' and 7000' elevation. I need the basics on the idle screw, altitude, and fuel mixture. I was guessing with 40 to 1.
Johnny

 

[steelespike]

Re: Montgomery Ward Seaking 7.5 HP Clinton engine slow idle back fire

48:1 fuel mix.
Backfireing at idle is usually an indication of too lean adjustment on the idle mix screw.Simply adjust it idling in gear.If adjustment doesn't help you'll probably need to rebuild the carb with special attention to cleaning.

 

[jhnyutah]

Re: Montgomery Ward Seaking 7.5 HP Clinton engine slow idle back fire

Thanks Spike. I will change the mix today. Can you give me any more detail on the idle mix screw. I know one of the three (?) adjust idle speed. Can I carefuly guess for the mix. I cannot locate a manual.

Thanks, Johnny

 

[jhnyutah]

Re: Montgomery Ward Seaking 7.5 HP Clinton engine slow idle back fire

Also, do you know the year of this motor? What is the best oil to use?

thanks again, Johnny

 

[steelespike]

Re: Montgomery Ward Seaking 7.5 HP Clinton engine slow idle back fire

Your motor is a 74-75
My aftermarket ser. manual is not clear about where the mixture screws are.But they sometimes have a spring coiled around them to keep tension so they hold their setting.The initial idle setting should be about 3/4 turn out from gently bottomed.The high speed initial setting should be 1 1/2 turns out.Sometimes the high speed screw appears more prominent while the idle mix may be appear slightly smaller and in a less prominent spot.Final high speed setting should be done first warm at speed then adjust the low speed idling in gear.Your idle speed adjust will be obvious because it acts on the external mechanism of the carb.The mixture screws screw right into the carb body.Some right on the face,some along the side.some into the bottom of the float bowl.On some motors the knobs may need to be removed to do the adjustments.Just put them back on in a median position.
My 89 generic service manual say use quality outboard oil.

 

[jhnyutah]

Re: Montgomery Ward Seaking 7.5 HP Clinton engine slow idle back fire

Thanks again Spike. I changed the mixture and set the high speed screw and the mix screw on the bottom of the float bowl. I also sprayed it with some carb cleaner. It seems to run well with a misfire every once in a while. Low idle is a lot better, but still dies sometimes without backfiring. I'll keep fiddling with it until I get it right. I might take the carb off and clean it. The vacuume fuel pump is loose and may be letting in extra air.

Thanks, Johnny