Most outboards are water-cooled. The way they do this is through a pump that runs cool water up to the powerhead. This is why it’s important to flush the engine after each use, especially if you run it in salt water.
Overheating can cause serious damage to expensive components in your engine. If you’re having problems with your outboard overheating, call our Fort Lauderdale mobile marine mechanic. In addition, here are some tips to help you diagnose the issue.
Thermostats
Examining its cooling system is one of the easiest ways to tell that your outboard is overheating. The water passages that run up to and around the engine are prone to build up of salt and gunk, which can restrict water flow and cause the engine to heat up.
In addition, the thermostats that regulate the operating temperature of the motor are also prone to failure and must be replaced periodically. The recommended intervals are often based on engine hours or years of use and it is critical to follow them to ensure that the proper temperature range is maintained.
Using your dash gauge to determine the normal operating temperature for your outboard is a good way to develop an index that lets you know when something has gone wrong with the cooling system. This allows you to detect problems with the radiator, or a problem with the cylinder head or gaskets before they get out of hand and your engine overheats.
Water Pump
Every outboard has a telltale stream of water that exits the powerhead, or “tell tale.” This flow is an indicator of cooling water passing through to keep the engine from overheating. If it isn’t flowing or the flow appears to be decreasing this can indicate a problem with the water pump, thermostats, or other areas of the cooling system.
Using a hose to flush the area of the lower unit where the water passes up into and around the water pump is a good way to check for clogs. Over time salt and gunk can build up in those passageways and slow down or stop the flow of cool water.
If your outboard overheats when you’re running it at higher speeds or during extended usage, there is likely a problem with the water pump impeller. These hard rubber blades can begin to curl, reducing the amount of water that is pumped through your motor. Keeping an extra impeller on hand is wise and replacing it periodically will help prevent overheating problems.
Intake
As with any other part of a boat, an outboard motor can overheat. Thankfully, most of the time it’s something fairly simple that can be fixed.
Over time, weeds, trash and other debris can build up inside the intake of the water pump, disrupting water flow. One of the easiest ways to check if this is the problem, is by simply looking at the output of the water pump. A steady stream of water should be flowing out, if not, it could be an overheating problem.
If this is the case, turn off your engine, and “crack” open the through hull valve to the sea strainer, then gently remove the sea strainer basket and see if there is any foreign object clogging the intake. Once everything is back together, start the engine and head home while watching the temperature gauge. If it continues to overheat, call for help. Alternatively, you can always give the engine a good dose of vinegar.
Output
Outboards take in water, run it through the water pump and then push out a steady stream of water to propel your boat. If your outboard isn’t taking in enough water or pushing out enough, it can overheat and internally damage itself. Check to make sure nothing clogs the water intake area and that there’s a steady flow of water coming out the engine’s output.
It may also help to keep a few tools and spare parts on hand. For example, you should have a replacement water pump impeller on hand to replace the one in your outboard’s water pump. This is the small propeller-like part inside the pump that rotates to suck water up into the engine. When this goes bad, it stops the water flow and can cause overheating very quickly. Check the owner’s manual to find the proper size of replacement for your outboard. Having a spare on hand can save you a lot of hassle and money.
