There are three basic types of boat motors: outboard two and four stroke, inboard gas, and diesel. The different types of boat motor repairs depend on the type of motor being fixed. Breaking the motor down into subsystems such as cooling, fuel, gear case, and motor can help to inform the repairs that are needed.
Cooling systems are essentially pumps that circulate water or coolant through the engine. The pumps have impellers and seals that eventually require replacement and repair. Some impellers are rubber and some are bronze, and each requires a different type of maintenance. Seals vary from lip type seals to two-piece mechanical seals, depending on the type of boat engine. The mechanical type is more labor intensive to replace.
The fuel systems on the different types of motors vary from carburetion to fuel injection, but all have filters, both primary and secondary, that require replacement and repair from time to time. Changing the fuel filter is a common maintenance procedure regardless of the type of engine. Carburetors require cleaning and tune-up occasionally, and fuel injectors need to be cleaned, tested, and replaced periodically, as well. Injection pumps, which are different from fuel injectors, also need to be tested and replaced as needed.
Gear cases are a common element of boat motor repairs. Such cases are quite different in type and size, ranging from just a few pounds to thousands of pounds each, but all require clutch maintenance. Different types of clutches will require different repairs. All need adjustment or replacement from time to time. Gear cases also contain gears submerged in oil, and the oil must be replaced on a regular basis. Failure to replace gear case oil may result in major boat motor repairs, which will likely be quite costly.
Boat motors are piston-operated engines that require a change of oil and filters regularly. The motor itself has pistons, rings, and bearings, all of which wear out and require replacement. When a motor is not running correctly, a compression test can be done to determine if the problem lies in the rings, valves, pistons, or cylinder head. Compression tests are done for all types motors. Checking timing is another procedure that is done on all motors. Conducting compression tests and checking timing are procedures that aid mechanics in determining which boat motor repairs are needed.