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Outboard Spares Blog - What Sand And Weed Can Do To Your Outboard

Culprit: Sand, Rock and Gravel

You can get propeller or gearbox impact damage from rock and gravel but where constant dredging of sand is not uncommon you do increase your risk of overheating your engine. Sand and gravel are experts at finding their way into your cooling galleries and blocking them up.

When working for a marine dealer years ago I remember a customer coming in very unhappy that his engine had broken down on him whilst being on holiday at Mallacoota (North East Vic) when he had it serviced a few weeks prior to his trip.His engine overheat alarm was constantly going off even though the water pump and thermostat assembly were recently replaced.Removing the gearbox found that the water pump was fine, however, when the thermostat cover was removed we found the entire thermostat housing and surrounding galleries were chock full of sand and gravel. It was like concrete.The bewildered owner couldn't believe what had occurred but later on acknowledged it probably happened when he was trying to get the boat off the trailer at a shallow sandy ramp on his first day.

Culprit: Weed

Won’t necessarily block the cooling galleries on the outboard but more so destroys water pumps and impellers.Ribbon weed (or similar seaweed)can be a problem in both shallow and deep waters, where it floats in thick clumps.It can block the intake on the gearbox housing that feeds the water pump restricting the water flow and causing the water pump housing to have insufficient lubrication for the impeller. The end result is a damaged impeller and/or complete water pump.

Getting stuck on a sandbank, driving through shallow channels, launching at a shallow or sandy/rocky boat ramp or driving through a patch of weed all seem harmless enough but all of these can cause damage to varying degrees.

Following the channel markers, trimming your outboard up and keeping an eye out for any changes in the environment you're operating your boat in is the best way of avoiding potential damage to the cooling components of your outboard. That doesn't mean you have to putt around at 5 knots but, just keep an eye out for the risks and avoid them where possible.