De-Wintersing Your Diesel Engine

As you can imagine we get numerous call outs for people in the early season, who have headed out for their first sail to find they have forgotten vital checks on their engine. Something that we do come across a great deal is Seacocks not being opened; this can have disastrous consequences, the obvious one being overheating.

This can be awfully alarming for our sailors out there as this will melt the exhaust; which can be firstly identified by smoke billowing into the cabin.

Getting your engineer to De-Winterise your engine is great but to ensure that you enjoy another season of trouble free motoring, learn how to de-winterise your own boat.

Before Launching

  1. Whilst the boat is out the water, check the exhaust is not blocked as this may have been plugged for the winter. In the water this would be an unpleasant job.
  2. Check fluid levels; water, oil, and not forgetting gearbox oil
  3. Check and grease the back of the throttle control mechanism especially if it is fitted to a compass binnacle as these can get very corroded.
  4. Re-fit the impeller or replace if necessary.
  5. Clean the bilges which can help you identify any leaks and don’t forget to check any bits that should of fallen off.
  6. Extremely important to check and replace any seriously corroded hose clips
  7. Re- tighten  the belts .For flat belts – you should be able to twist it through 90 degrees. The general rule of thumb for your v-belt is around 12mm of play on the belt if you apply reasonable pressure.
  8. For flat belts – you should be able to twist it through 90 degrees.
  9. Check and grease the stern gland if required
  10. Check the sea cocks are open and the fuel system is configured correctly i.e. supply and return valves are open


  1. Flat batteries are an extremely common thing for us to get called out to.
  2. We would recommend you replace your batteries every four or five years.
  3. Batteries should be removed and charged every month where fluid levels should be checked also. If this is not the case and you charged your batteries by shore power. Don’t forget to check you fluid levels regularly.
  4. Once your engine is up and running again, ensure your alternator is working correctly
  5. Battery voltage should remain at between 13.5 and 14v on a 12v system.  15v and higher you will have a problem.

On the water

  1. Once you have launched, take some time to ensure all is well. Check around the stern gland of any signs of leaks.
  2. Also visually carry out some inspections, pay particular attention to the jubilee clips or parts which have been repaired or in some cases replaced over the winter which maybe loose.
  3. Once fired up carry out another inspection on the engine, parts will be moving so please take care when doing so.
  4. Confirming that your boat is tied up safely put the engine into gear. This will bring the engine up to temperature.
  5. Check only water is coming out of the exhaust. If you have steam coming out and no water turn the engine off again. This well mean your engine will overheat and your engine salt water system may need to be primed.

Get motoring

  1. By following the above steps will ensure you have a trouble free season.

Take care out there.

Want to learn even more about diesel engine maintenance?  You can sign up for a RYA one day diesel engine course.  Courses take place in Hamble from September through to April. Call the office for more details 0238 045 800 / 0800 88 55 00