On an outboard without fuel injection, the carburettor mixes the fuel with air. Its jets are tiny, so dirt, water or varnish from fuel that has evaporated soon block them, and the engine runs badly or won't run at all. Most carburettor problems are fixed by cleaning it, and an old one may need a repair kit with a new needle, float and gaskets.
PHOTO Dangar Marine Boat Guide
The carburettor has debris blocking the jets
Open ›A very common reason that outboard motors run badly is from dirt in the carburettor(s). This can be from water or other contaminants in the fuel, perished fuel lines breaking up and putting debris into the fuel or varnish from fuel that has evaporated after the engine has been sitting for a long time.
Cleaning a Yamaha 15HP carburettor
Open ›Dirt or water in the carburettor causes many outboard problems. I take the carburettor off a Yamaha 15HP two-stroke, strip it down, and clean the jets and galleries with carb cleaner and compressed air.
Unblocking a carburettor jet on the water
Open ›An outboard running lean on the water may have a jet blocked with dirt or water. I show how to clear it by raising the revs and choking the carburettor with a rag.
Fitting a carburettor repair kit
Open ›When cleaning isn't enough, a carburettor repair kit replaces the parts that wear out. I fit a new float needle, pivot and gaskets, and compare a kit with single parts or a new carburettor.
Making a paper carburettor gasket
Open ›When you can't get the right gasket between the carburettor and the engine block or reed valves, I show how to make one from gasket paper using an oil imprint, wad punches and a knife.
Synchronising the carburettors on an outboard will make it run smoothly
Open ›An outboard with several carburettors runs smoother once they're synchronised, and a two stroke can stop sneezing. I balance the vacuum on a four stroke and check a two stroke's butterfly valves open together.
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