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Most marine exhausts are water cooled, with water from the engine’s raw water cooling system used to cool the exhaust gas. The water and exhaust gas mix together in the injection bend, where it turns into steam before cooling and condensing back into water which then makes its way out of the hull via the exhaust system.

Exhaust system inspection       

With the boat ashore, it is wise to inspect the exhaust system for corrosion damage, especially around the injection bend:

  • Injection bend – this is where the raw water cooling system meets up with the exhaust gases to in order to cool the gases enough to prevent the flexible rubber sections of the exhaust from melting. Check the condition carefully, looking for any signs of corrosion.
  • Exhaust piping – look for external signs of deterioration in the flexible rubber piping, connections and clips, checking the condition of the double clips all along the system. Any signs of white crystals indicate there have been sea water leaks.

Smoking exhaust

If you have noticed the engine exhaust smoking a lot during the sailing season this can indicate a number of potential problems with the engine that may need to be rectified. It is normal for an engine exhaust to smoke until it is warmed up so you only need be concerned if the exhaust is smoking after the engine has fully warmed up.

The colour of the smoke can be a guide to what might be wrong. White, blue or black smoke from a diesel exhaust indicates there is a problem. White smoke has two general causes: overcooling where proper combustion is not taking place or worn piston rings. Blue smoke comes from burning oil. It can be caused by worn valves or piston rings. Black smoke typically indicates partially burned fuel, worn injectors or clogged air filters. The chart below looks at possible causes and solutions. To help solve the mystery you may need advice from your boatyard mechanic.

White exhaust smoke

 

Possible cause

Solution

Blocked injectors

Service the injectors

Water or air in the fuel

Defective seals, possible leaking head gasket

Check the breather pipe is clear and not obstructed

Remove and clean out

Reduced cooling water flows

Check the raw water system

Blue exhaust smoke

 

Engine oil level too high

Check the oil dipstick. If too high, pump out some of the oil

Worn valve guides and seals

Replace oil seals

Piston ring and bore worn, giving a low compression

Get compression checked by a boatyard pro

Leaking turbocharger seal

If fitted, get the turbocharger checked by a boatyard pro

Black exhaust smoke

 

Blocked air filter element

Inspect and replace

Inadequate ventilation in engine compartment

Check the ventilation isn’t blocked

Blocked or damaged exhaust hose

Check the exhaust hose isn’t blocked or restricted in any way; internal inspection may be required as inner layers of exhaust flexible hose can collapse

Malfunctioing fuel injection

If the airflow is unobstructed and the engine not overloaded, poor injection could be the problem.

Over pitched propeller – engine will not reach its full rpm

Check the engine will reach full rpm in neutral; if it does not get the propeller checked / re-pitched if necessary

Accumulated debris on hull

Inspect and clean if required

 

Keeping boat records and doing checks

A boat’s records should provide information about maintenance schedules, when major work was done and when equipment was replaced or added to the boat. Without this information you are left guessing when things are likely to need replacing in the future and also what the costs are likely to be.

Narrowboating on the Kennet and Avon Canal

A recently cancelled sailing event I was due to take part in left us with a free weekend in the diary. Given that my wife and I were celebrating a bumper wedding anniversary and the weather forecast was for fine weather, we decided to hunt around for a last minute canal holiday.

Rudders and steering systems – Part 2

One thing all rudders have in common is that they have three main parts that need to be checked: the rudder, or a steerable drive leg in the case of many power boats; the system that joins the rudder to the steering; the steering control itself.

Boat Engine Safety Checks

  Boat Engine Safety Checks Every skipper needs to make regular essential boat engine safety checks. Below you will...

Winch Servicing

It is not essential to service the winches when a boat is ashore, but if time allows I prefer to do this maintenance job when the boat...

Rewiring a boat – overcoming the challenges involved

Skippers need to have a basic knowledge of boat electrics, to avoid potential problems and to be able to solve them when they happen.

Top five windvane self steering installation questions

Top five windvane self steering installation questions answered by Sarah Curry of Hydrovane International Marine, courtesy of Viki Moore from Island Cruising NZ

A simple guide to understanding tides when passage planning

Understanding tides when passage planning When planning a trip in tidal waters, check the tides before going afloat. Use...

Sailboat rig checks – Part 2

In part two of Sail boat rig checks we run through some useful rig maintenance tips and then finish with a brief look at what a professional rig check involves.

Sailing into a storm

Weather forecasting has become increasingly accurate, but despite this, I was caught out recently by a forecast that considerably underestimated the wind strengths and consequently was sailing single handed in to a Force 8 gale, which proved to be challenging!

An explanation of the IALA maritime buoyage systems – IALA A and IALA B

What are the differences between the two IALA buoyage systems, IALA Region A and IALA Region B, and where are they used?   As recently as the 1970s...

Antifouling for leisure boats – Part 2

To prepare for antifouling, as soon as your boat has been lifted out and pressure washed, you need to check all the surfaces of the hull below the waterline, remove any remaining barnacles and check for blisters.

Keel design – options to consider when choosing a yacht

Keel design is constantly evolving and nowhere is this more apparent than in modern racing yachts such as the Imoca Open 60...

Boat maintenance below decks

While most interior maintenance work can be done when a boat is afloat, some jobs such as servicing the seacocks have to be done ashore. It makes sense to do any major interior repairs and improvements with the boat hauled out in the boatyard.

Saildrive maintenance

There are less maintenance tasks to carry out on a saildrive transmission than on a traditional inboard shaft drive system with its associated stern gear. However, there are a few critical things that require maintenance, as recommended in detail by the engine manufacturers, and should be adhered to.

How to Avoid Collisions At Sea With The ColRegs

      Every Skipper Needs Accurate Knowledge of the IRPCS ColRegs As a responsible skipper it is every skipper’s duty to learn and apply the IRPCS...

Sailing to windward – how to take advantage of wind shifts

For most sailors, sailing upwind is the most exhilarating point of sail as you tack your way to your destination. Sailing to windward is a bit like zig-zagging your way up a mountain road through a series of hairpin bends – great fun but also calling for concentration and hard work.

Essential Knots: Figure of eight

Essential Knots: Figure of eight Use: Stopper knot, prevents a rope from being pulled through a hole e.g. through a block or...

How to use tides and currents to your advantage

If you are contemplating a cruise through tidal waters and strong currents, then planning your trip carefully in advance is essential to enable you to take advantage of favourable tides rather than constantly fighting against them.

Estimating your position at sea

Navigators use a combination of techniques to estimate their position at sea. The primary method used today is GPS (Global Positioning System), a network of 24 satellites that became fully operational in the 1990s and was originally restricted for use by the United States military.

How to read nautical charts

Whilst most sailors today rely on GPS to find their way at sea, nautical charts are a crucial tool for any sailor to navigate safely and effectively. Here is a reminder of some of the basic steps involved in reading a nautical chart:

Avoiding personal dangers at sea

In order to stay safe at sea, we need to know the risks we are facing and to be aware of any personal dangers we could possibly encounter. Here are six of the most common potential dangers individual crew members should be aware of.

Pleasure craft safety equipment recommendations

Safety equipment is an important part of boat preparation and it is advisable for all pleasure craft skippers to check their vessel is...

Engine failure at sea – keeping the boat safe

If the engine stops when you are underway, or your have to shut it down when a warning buzzer sounds, you also need to make sure the boat remains safe. It’s important therefore to recognise situations in which the boat would be immediately put in danger if the engine were to fail.

Boat electrics inspection checklist

With the boat ashore, here are some recommendations for carrying out a boat owner electrics inspection. Safety is always paramount so remember to do the checks with the batteries off. Wearing a head torch helps, make notes as you go and only tackle a repair if you are 100% sure you know what you are doing: