Vehicle Tips with Jackson Brown Auto & Marine - Marine engine servicing and maintenance

The cooling system is the most important system of any marine engine, inboard or outboard. Because it operates in a very demanding and corrosive environment (the ocean) the cooling system needs regular maintenance to keep it efficient and keep the engine from overheating and breaking down. Cooling system issues caused by lack of maintenance are by far the most common cause of outboard or inboard engine failure.

Flush the engine

You may have heard of an impeller on a boat engine, this is a pivotal part of the water pump that supplies water to the engine for cooling. The impeller is made of rubber and flexes when it is spinning, pumping water up to the engine. It cannot be operated without water for any length of time (20-30 seconds running without water is enough to wear out an impeller). Running the engine without a water supply will wear the rubber off the vanes and cause it to lose efficiency and give overheating issues. 

Please always have a water supply connected and run your engine before going to the boat ramp. Also flush the motor for 10 minutes after every salt water use to remove the salt from the cooling system.

A motor that does not get used will cause the impeller to take a set meaning the rubber impeller gets a memory of where it was sitting for a long time and will not flex properly to pump the water next time it is used. 

Engine serviced annually

If you have not used your boat much it is worse for the motor than getting regular use as sitting around will allow any salt in the cooling system to crystalize and grow, blocking cooling galleries, thermostats and relief valves. 

As such it is almost more important to get your boat serviced once a year when it is not used much. The service should include checking the cooling system – removing the gear case and checking the impeller, removing the thermostats and relief valves for cleaning and testing. This is also the time to lube all bolts and drive shaft and prop shaft splines to avoid expensive repairs caused by seized bolts or splines next time it needs to come apart.

Under-use a problem

Any fuel over six months old and exposed to air, as it is in under-floor tanks via the breather tube, will go off if fuel conditioner is not added to it early on.

Water in the fuel happens when an under-floor tank is left half full exposing the sides to air and moisture condensation, it is best to leave it full.

Other under-use problems can include blocked or full water/fuel separators (not changed annually), hard starting due to gummed up carburettors (from the fuel in the carbs evaporating which leaves excess oil and varnish and gum deposits, drain the carbs before storage), flat batteries (they need to be charged once every two months when not in use or will have a shortened life), seized steering (needs to be operated and greased monthly), and trailer wheel bearings and lights failing (always caused by water getting in and sitting and corroding).

Most outboard manufactures recommend removing the power head and stripping it to clean out the cooling galleries and to replace all gaskets and seals once every 10 years as preventative cooling system maintenance. This is not always needed after 10 years but should be done well before the outboard reaches 20 years old. 

If you have any questions, comments and concerns, please contact us at Jackson Brown Automotive and Marine, 194 Molesworth Drive, Mangawhai Heads, 09 431 4814 or www.jacksonbrown.co.nz.