Outboard carburetion systems are generally pretty rugged and reliable. Unless you have many running hours on a modern outboard, this system gives little trouble.

Older, pre-alcohol days motors have fits when presented with "extended" fuels, and should you have one of these, I strongly recommend you upgrade the fuel system components.

The worst enemy of fuel systems is the fuel itself left to spoil in the unused motor. Proper preparation for storage of motors in seasonal climates is a MUST to avoid this nasty problem. Here is my storage tips page.

If your engine is suffering from a suspected fuel problem, here's how to check for dirt in the carbs: you will find a screw in the lower portion of the float bowl on almost all outboard carburetors (generally the main high speed jet is located immediately behind this).
On Chrysler/Force concentric bowl carburetors you will have to take the float bowl clear off to look.
IF there is white powder or jellylike translucent gleep you have water that has been sitting in the fuel system, the carburetor will have to be cleaned and the source of the water isolated and corrective action taken.

Plain clear water indicates only that you need to find out where it came from as above. Shouldn't hurt it any, but small low speed passages may have water in them as well and you will have to clear them with compressed air.

Find brown goo, brownish or greenish deposits or some stuff that looks like tree sap? You have a case of varnish and will need to examine ALL the lines as well as the fuel pump diaphragm for deterioration from the bad fuel. It eats everything.

Varnished bowl: I have found the use of OMC Engine Tuner will clean the carbs without exposing you to caustics, has no unpleasant odor and it rinses away with water. Similar products are available from other manufacturers (such as Mercury Power Tune).
Many of today's modern engines have some sort of oil premixing or injection system; you need to examine this system closely as well. If you are experiencing excessive oil usage on an Evinrude or Johnson equipped with the VRO system, look for an air leak on the fuel side. Air leaking will cause the oil side to add too much for the imaginary gas (that is actually air).

  The motor cover is a machinery guard. Use caution when conducting tests on a running engine.  

IF you wish to service or repair your own fuel system, I HIGHLY RECOMMEND you obtain an OEM model-specific service manual to help you. We have most linked Right Here at Mastertech.

 

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