Select Page

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

 

Anchoring – getting it right

If you can set an anchor correctly with confidence and know your boat will be safe in a secure anchorage, then you can rest in comfort and will not...

First aid at sea basics

At least one person on board should be trained in first aid and know how to administer the contents of the first aid kit, ensuring there are adequate supplies for the planned duration of the trip.

Top Tips For Learning: ColRegs Boating Rules Of The Road

Colregs Boating Rules Of The Road
The International Regulations for Preventing Collisions at Sea (COLREGs) are a set of rules designed to prevent collisions between vessels. They are essentially the “rules of the road” for boats. Some key concepts within the COLREGs include:

ColRegs – avoiding collisions at sea

ColRegs - avoiding collisions at sea ColRegs Rule 8: Action to avoid collision (a) Any action taken to avoid collision shall...

Safety at sea principles

Safety at sea is not as simple as just spending money adding shiny new emergency equipment such as liferafts, danbuoys, distress flares, EPIRBs and so on.

Cutless bearing replacement

Cutless bearings can last for many years but if the propeller shaft is out of alignment they will wear through more quickly. If you have noticed a clunking sound when motoring then it could be a worn cutless bearing that is causing the problem.

Competent crew skills: arriving and leaving a berth

Skilled boat handling is needed when entering or leaving harbour. Crew tasks include preparing the mooring lines and fenders before docking and...

Man Overboard Drill

How to respond to crew overboard under sail • Keep the MOB in sight • Tack into the heave-to position, do not adjust the...

Sailing Safely at Night – Best Practice

Sailing at night can be a magical experience – the peaceful solitude, starry skies, and gentle lapping of waves create an unforgettable atmosphere. However, nighttime sailing also presents unique challenges and risks that require careful preparation and vigilance. This comprehensive guide will cover essential safety practices to ensure your nocturnal nautical adventures are both enjoyable and secure.

ColRegs Rule 14 – Head-on Situation

  ColRegs Rule 14: Head-on Situation (a) When two power-driven vessels are meeting on reciprocal or nearly reciprocal...

Pre-start engine checks

According to the Royal National Lifeboat Institution (RNLI) almost one third of emergency call outs at sea are caused by mechanical failure. Many engine breakdowns are avoidable. The best way to avoid a breakdown is to carry out pre-start checks before heading out to sea.

Crew Overboard Drill – Updated

How to respond to crew overboard A Man Overboard (MOB) drill is a crucial safety procedure that every boater should practice regularly. It simulates...

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!

Antifouling for leisure boats – Part 4

Applying antifouling. Antifouling is best applied on a dry, calm day. It is best to apply the antifouling in the middle of the day to ensure the hull is dry and as warm as possible.

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.

2023 Rolex Fastnet Race – Part 3

This is our third and final article about the 2023 Rolex Fastnet Race. It is a first hand account by Simon Jollands who was one of the crew of Lancelot II, a Beneteau First 40 skippered by John Gillard.

Fractures, sprains and dislocations at sea

Moving about a boat at sea often results in a few knocks and bruises, but if a crew member has a fall or major bump and is in serious pain, they should be examined and treated accordingly.

Tidal terms and definitions

Getting to grips with tidal terms and definitions can seem a little daunting, even to the most experienced sailors! Here we look at some of the key terms and definitions associated with the language of tides.

Boat engine basics

Boat engines come in all shapes and sizes and include inboards, outboards, petrol, diesel, electric and hybrid systems. Some engines are...

Common marine electrical problems

Most problems with marine electrical systems arise from four possible sources, a lack of maintenance, a poor standard of initial installation, insufficient battery capacity, or ineffective charging systems.
Water ingress is a frequent issue – salt water can corrode contacts very quickly. If connections are not scrupulously clean – or are loose – resistance will be increased, resulting in progressively reduced power.

Boat interior varnishing

Most boat interiors have a combination of varnished and painted surfaces including solid wooden joinery, plywood laminates with thin hardwood veneers and glass reinforced plastic. When making your assessment of what you are going to do, bear in mind that the varnishing process consumes a lot of time, especially if the existing surfaces are in poor shape.

Steel hull maintenance

A steel boat owner’s biggest enemy is corrosion. You don’t have to worry about osmosis or rotting timbers, instead rust is the number one issue that will keep you awake at night.

Safety Briefings – leave nothing to chance

Before giving your crew a safety briefing, it is worth considering the specific circumstances of the planned trip, the...

Boat engine fuel system

If engines are installed and serviced correctly then most marine engines are very reliable, but one of the most important parts of the engine to check and service is the fuel system.

Boating Rules of the Road – International ColRegs

    International ColRegs Rule 7: Risk of Collision Anyone who is responsible for a vessel at sea, from the...