Clogged Carburetor Diagnosis 2007 5HP Mercury / Tohatsu Outboard Basic Maintenance

The most common problems that we see with outboard motors of all sizes brought in for service at Highland Outboards are related to carburetors. Performance issues or failure to start/run are often the result of buildup of unwanted materials in the small passages, jets, and valves inside the carb. The effects that ethanol blend gasolines have on small engine carburetors are becoming widely recognized in the industry. The buildup of residues within the carb causes all kinds of problems that can potentially ruin a good day on the water. The typical symptoms of ethanol-related carb problems are:

Hard/Impossible to start
Motor starts, but dies at full throttle
Engine does not idle or run without choke

The good news is that fuel additives are available to help neutralize ethanol and prevent the breakdown of today's gasoline mixtures. We recommend the use of ethanol treatment and stabilizers every time you fill-up your outboard gas tank.

In this video we show a typical clogged carburetor diagnosis including disassembly and proof of root cause. This example is shown on a 2007 Mercury ME5M 4ST 5HP outboard, but would be very similar on Honda, Evinrude, Johnson, Yamaha, or other 4-stroke and 2-stroke outboard motors.