Page last updated July 17, 2008



Routine Maintenance

Daily Checks Prior to Boat Outing

As you get your engine up and running, you will need to do a few things to keep running. Here are a few tips for keeping it in good working order. Does not matter if you have Mercury outboards, a Nissan Outboard or an Evinrude, these checks will apply to all engines.

  1. Check oil tank for proper fill level (may not apply to all engines)
  2. Check for adequate fuel and that fuel vent is open. Failure to open vent will lead to warped tank and possible starting problems.
  3. With engine in the up position, check for oil buildup near prop area. This could indicate a leak in the seals. See my water pump page for example. At times, the buildup could be carbon deposits collecting from burnt fuel. It could also be an indicator that the engine is running rich, and as a result, there will be un ignited / un burnt fuel being expelled to exhaust area causing a buildup.
  4. Check prop for damage. A simple brazing rod method can be used to repair damaged props or you can take to repair shop to do the repair.
  5. Check for rope / fishing line wrapped around prop. Damage could result to seals if rope eats away at them.
  6. Check fuel lines for coating of fuel. This could indicate fuel leaks in lines. Replace cracked, leaking lines if found.
  7. Check all bolts that are holding the engine in place. Vibrations can make them loosen. Check transom for wear, cracks, bulging due to engine weight. Ensure all bolts are clamping and that they are not corroded in place. Place a light coat of locktite after inspection to avoid loose nuts and bolts.

Monthly Checks

In between trips, there are some tasks that will need to be done. These tasks tend to prevent major failures and require a little bit of your time. But time invested will payoff by preventing major priced repairs from needing to be done.

  1. Look at engine block and inspect for corroded areas. Corroded areas should be marked and then inspected for leaks while engine is running. Corrosion is obviously not good and could be a sign of worse things to come or simply a leaky cover is allowing moisture to collect where it should not.
  2. Check all electrical connections for corrosion. Make sure battery power is disconnected prior to performing this task. Some connections may have rubber boots. Carefully lift boots and inspect. Clean all problem areas with wire brush and coat with anti-corrosion spray (bulldog) . If nuts are rusted, ensure you replace with the same type material nut (bras, stainless steel, etc). During initial inspections, clean all bolts with wire brush and coat with anti-corrosion spray to prevent future problems. If you find a nut bolt that is not supplying pressure to a gasket (visibly loose), tighten only enough to lightly seat. If the nut / bolt is supplying pressure for a gasket, it is best that you do not loosen unless you are prepared to replace gaskets. At times, removing pressure from a gasket will no longer allow it to seal properly, so be weary of touching any of those nuts / bolts.
  3. Snug up all mounting bolts holding fuel pump, oil filters, etc. Be weary of retorqueing anything that has a gasket underneath it. You DO NOT want to over-torque these areas as over-torqing could result in blown gaskets. You should only snug these up if you have a leak or they are visibly loose or can be loosened by hand.
  4. Check fuel / water separator. Clean and re-install.
  5. Check sacrificial zinc-anode on engine. These will corrode before engine does. If this is looking bad, replace anode or your engine will end up corroding much more rapidly.
  6. Check battery terminal connections and battery levels; fill if the battery allows you to fill it.

Quarterly Checks

These checks will be in 3 month intervals. These are thorough inspections and any deficiencies should be corrected on the spot.

  1. Lubricate all moving parts. Grease fittings should be cleaned, inspected and greased until old grease is expelled.
  2. Inspect propeller again for any damage. Brazing rods can be obtained from local hardware store and repairs can usually be made without much assistance. Propellers run expensive and any damage will certainly reduce performance. Fill in burrs, repair damage yourself or take to qualified marine dealer.
  3. While prop is removed, it is a good idea to lubricate prop shaft with some waterproof prop grease so that it does not corrode / freeze in place. Ensure you do not reuse nylon self-locking prop nut. The plastic / nylon inside the nut is usually not reusable.
  4. Change the gear case oil. When draining, inspect for milky substance and metal shavings. If milky, then you
    may have seals that are bad. If large metal shavings / chunks, then you may be slipping, grinding gears or they are not locking in place. May need additional work or gears adjusted. See lower gear case repair page. Fine particles of metal are normal and should be fine but monitor. To refill, use appropriate lower unit gear case lube oil. The oil must be inserted from the bottom up. Basically, with top and bottom plugs off, push the oil through the bottom. The oil container usually allows you to fit nozzle into drain plug. Squeeze container slowly until oil starts to come out from the top plug. Carefully have someone else seal top plug as this will create a vacuum and allow you to easily place lower plug in place without creating a mess and also will prevent you losing a lot of oil. Try to obtain a magnetized lower drain plug so future metal shaving will not cause additional damage to gears and install new seals / o-rings on drain plugs.
  5. Clean cooling system by flushing engine with fresh water using a flush adapter. Make sure adapter stays in place. A better solution would be to place a plastic rubber made garbage can large enough to accommodate the engine with water high enough to allow water pump to function. This method will also allow you to check that seals are not leaking oil out of lower unit gear case. If it is leaking, you will see an oil film in water appear when engine is off.
  6. If your unit is fitted with thermostat and it is easily accessible, it is advisable to clean and inspect the device out yearly. As you can see from the picture in the thermostat page, this area can build up a lot of debris. Mine had corrosion and sand. It pretty much corroded much of the surrounding metal to the point that a new exhaust cover was needed. I recovered and resealed mine with some RTV gasket maker around the pitted metal. This allowed the rubber shield holding the poppet valve in place to seal. If I could find a replacement exhaust cover I would purchase, but engine was so old, I had to make do. The thermostat can be cleaned with wire brush.
  7. Inspect impeller and replace if you see any marring / scarring. Some manufacturers recommend to replace impeller seasonally, it is up to you. If failure of impeller would be a dangerous thing for you, then replace it seasonally. I boat on lake and carry paddles, so if mine fails, I can row to shore. Every two - three years should be fine unless engine is used constantly.
  8. Check compression on cylinders
  9. Check steering cable for marring, corrosion, lubricate and adjust if needed.
  10. Check batteries for charge and corrosion. Refill with water if necessary.

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