How to care for your boat’s engine — part two
Engine guru Andrew Norton explains how to properly care for your boat’s engine to ensure it performs better for longer.
If you missed Part One of this article, you can access it here
Changing spark plugs
You’ll need:
- Recommended heat-range spark plugs
- Suitable spark plug wrench
- Suitable new ignition leads
Spark plugs should be changed according to the intervals mentioned in the owner’s manual and when the engine is cool.
To change your spark plugs, carefully pull on the ignition lead connecting boot — not the lead itself as this could damage the wiring inside. Insert spark plug spanner and remove plugs, making sure nothing falls down the spark plug holes.
Use a feeler gauge to check the spark plug gap is correct and carefully inspect the electrodes for any pitting or excess wear. If OK, fit a new washer to each spark plug and carefully reinsert using only your fingers — using a wrench could damage the cylinder heat threat, particularly in an aluminium-head engine. Tighten spark plugs to engine manufacturer’s recommended tension and reattach the spark plug leads.
If the spark plugs are worn it’s better to fit new ones after checking the electrode gap is correct.
Quick tip: It’s a good idea to check the leads while fitting new spark plugs. If these appear damaged or frayed, it’s cheap insurance to fit new ones.
Fuel system cleaning
You’ll need:
- New in-line filter for small engines
- Needle-nose pliers for removing the clips and attaching in-line filter
- Clean petrol to wash fuel tank pick-up screen
Ensuring your fuel is clean is essential for consistent engine performance. However, it’s one area that’s frequently overlooked when performing regular engine maintenance.
All engines with underfloor fuel tanks need a RACOR (made by Parker Hannifin) water-separating fuel filter, which should be checked frequently and drained if any water is present. It’s important you consult the owner’s manual as to the correct filter to use as water-contaminated fuel can really damage EFI injector nozzles.
With smaller outboards that use portable tanks, an in-line or bowl type of filter next to the powerhead, plus the fuel pick-up line screen, will usually be sufficient to stop contaminants reaching the carbie. However, it’s best to clean bowl-type filters (usually 15hp and above) at regular intervals of every six months or so. This is done by simply discarding the in-line filter and inserting a new one.
Oh, and don’t forget portable fuel tank maintenance!
Impellers
You’ll need:
- Suitable replacement impeller
- The right-sized socket wrench for unscrewing the cover plate
- New cover plate washer in case the old one is damaged
Outboards
Due to a few complexities, replacing the impeller is a job best left to your local outboard dealer.
Sterndrives and inboards
Unless your sterndrive has a cooling water impeller in the leg, saltwater cooling impellers are usually easy to replace once the cooling water intake sea cock has been closed.
Remove the cover plate, slide out the rubber impeller while making note of the vane curvature direction (or take a pic on your phone) and check for wear on the vane tips. If the wear is minimal, the impeller can be used again. Make sure you insert the vanes in the right direction — if installed backwards the vanes will tear when the engine is started and need instant replacement.
This is also a good time to check for other damage such as checking the sea cock for leaks and damage to the intake hosing connection to the raw water impeller. You can also check for leaks around the freshwater impeller housing if heat exchanger cooling is fitted.
Seals
You’ll need:
- Box wrench for removing propeller nut
- Needle-nose pliers for removing propeller cotter pin
- Water-resistant grease for prop shaft if shaft seal is undamaged
- Spare cotter pin for reinstalling prop if seal is OK
Every six months, you should remove the propeller and check for any stray fishing line around the prop shaft and gear case seal. If the latter is damaged, saltwater will seep into the gear case and rust the steel pinion and drive gears, plus the clutch dogs, even though they are covered in lubricant.
If you suspect the seal is damaged, unscrew the gear case drain screw and check for water. This will trickle out before the oil, which will probably be an off-white colour as it’s emulsified with water. If you find water in the gear case, the outboard should be taken to your local dealer or a reputable outboard mechanic as soon as possible. They’ll need to strip the gear case, remove the gears and check for corrosion.
Now get started!
Regular maintenance is the key to engine longevity. Just make sure you don't take on more complex jobs without having a service manual handy and a fair idea of the process. There are few things more disheartening than starting a job and not knowing how to finish it! That being said, if you're up for it then the DIY option is a good way to save some bucks. Plus, there's the satisfaction of doing a job at your own leisure and getting to know your investement better in the process!
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How to care for your boat’s engine — Part One