A Brief Overview on what Yacht Engines need to Last
Virtually all modern yacht engines are diesel engines however there are some other engines which are found on smaller yachts and high speed yachts.
All yacht engines have common requirements which will allow them to operate reliably for long periods:
- Enough Air – Yacht engines require lots of fresh air for combustion. Engine compartments must be able to provide this even if it is forced in via fans. The ideal situation is to pull air into the engine room via the top deck. The air is not as salty in ocean conditions and through fans that are variably controlled to provide positive pressure on demand. Controllable flaps shut off the supply of air in the event of fire.
- Clean Fuel – Water and particulate matter must be filtered out. Most used yacht engines are equipped with pre filters such as Racor, to filter water and particles down to 10 microns before the engine filters which take it down to 2 microns. Fuel quality for yacht engines is more questionable the further yachts travel from populated areas, therefore it is imperative to have good fuel cleaning equipment on board.
It is a good idea to keep fuel tanks full so that water condensate does not collect. Water aids an environment allowing for a fungus to grow in fuel. This fungus can quickly clog filters and shut down operation.
Speaking of such, there is a little known device known as an RCI fuel purifier which scrubs contaminants to next to nothing before it hits the paper (Racor or other) filter. These are very inexpensive and easy to install. See yachtflush for more information on these easy and valuable services.
Yacht Engines Also Need These Services to Survive Well
- Proper Loading – Yacht engines perform and operate best with correctly sized propellers which should be kept clean. Engines must turn up to rated WOT (wide open throttle) and propellers should match this engine parameter closely. If not, there is a chance that the yacht engines will not load properly and have a life reduction.
- Clean Oil – Yacht engines require oil and lubricants to be changed at regular intervals. Most modern yachts have built-in pumps with hoses and valves making this an easy task. Talk to your engine dealer about the possibility of using synthetic oil instead as a longer lasting alternative to standard engine oil. The extra cost may be worth the longer intervals between changing oil and lubricating your engine better. A new technology is available for further filtering oil by a centrifugal method which can be easily installed as a bypass filter.
- Efficient Cooling Systems – The cooling system and raw water pump must be serviced on a periodic basis. Things grow in salt water to the detriment of cooling systems. This is the engine’s heart and something which many owners overlook. Note that new methods allow for descaling procedures without taking apart the units. See yachtflush for more information on descaling engine cooling systems.
It is argued that modern large diesel engines, especially with high horsepower ratings, are not designed to operate at slow speeds. There is debate among professionals in this regard. However, sportfishers put on many hours at slow speeds without detriment. The common agreement is that engines of any type must be broken-in correctly when new or overhauled. They should be run up to high speeds at least periodically during every day of operation (to blow out soot).
Note that many popular yacht engines are maximized for horsepower. It is possible to get more life out of an older engine by ‘de-tuning’ it. This is usually accomplished by changing injector sizes.
Get your Oil Analyzed Regularly
It is a very good idea to have oil analyzed (even transmissions) every oil change, similar to a blood work-up – as one can often catch problems early before they get detrimental.
Yachts for sale which were built before 2000 would most likely find either Detroit Diesels (GM) or Caterpillar.
Detroit Diesel Yacht Engines
Detroit Diesel (GM’s) are a two-stroke diesel engine, which means that it completes its combustion and exhaust cycle in two strokes. The advent of clean emission mandates forced these engines into obsolescence and have since been replaced by four-stroke engines.
Mechanically controlled and governed up until the mid-1990’s with the DDEC series, these yacht engines pioneered the electronic controls which are now commonly found on most modern diesel engines.
Most commonly found in yachts prior to 1998
- 6V71 (rated between 210 and 480 hp)
- 12V71 (various ratings between 550-900 hp) (the 1271 is two 671’s put together – 71 referring to the cubic inches per cylinder – either 6 or 12 cylinders). !@V71’s engines are the most common engines found in older US yachts today.
- 6V92,(550 hp)
- 8V92 (710 hp)
- 12V92 (1050 hp),
- 16V92’s(1350 hp) (these engines eventually obtain the higher ratings via electronic controls).
These yacht engines were famous for plenty of low-end torque and simple mechanics. Yet they are noted for shortened intervals between overhauls when operated (or loaded too hard) and operated in hot conditions with not enough air. If an owner takes care to maintain and operate these popular yacht engines at slower speeds, they last quite a while.
Despite controversy otherwise, popular GM Detroit Diesel engines still have parts available. They are relatively simple engines and often repaired worldwide without specialty technicians.
Caterpillar Yacht Engines
Caterpillar – Noted prior to 2000
- 3208 (rated between 375 -425 hp)
- The inline-6 series engines started coming out in the late 90’s with the 3116 (350 hp), 3126, (450 hp),3176-3196 (660 hp)
- 3406 (800 hp) – Still in production as the C15
- 3412 (a V12 engine commonly rated between 1000-1450 hp ) – Still in production as the C30
All of these early CAT 6 cylinder engines suffered from some issue or another. The point is that all yacht engine manufacturers have issues with engineering flaws. The important thing is how they take care of it – and CAT developed a good program to deal with issues.
The newer models of these same engines – the C7, C9, C12, C18, C30, C32 – all have been reliable and are one of the two predominant engine manufacturers in today’s yachts. The CAT 3512 is the powerhouse for the larger yachts.
Modern emission requirements have brought the advent of the modern electronically controlled diesel and high-pressure injection service to more efficiently control fuel injection. Most engine manufacturers refer to this technology as ‘common rail’ while CAT refers to it as ‘ACERT’.
MTU Yacht Engines
MTU of Germany merged with Detroit Diesel in the late 90’s and developed a series of popular 4 stroke engines – the 8V2000, 12V2000, 16V2000, 12V4000 and the 16V4000 engines.
The Series 60 engine has also been a very popular model and long upheld in the trucking industry. Many of these yacht engines are found on today’s yachts and have held up quite well. Some of us wonder if their parts are made of precious metals due to the high cost.
MAN Yacht Engines
MAN has been a popular German engine in used yachts – especially sport fishers, because of its superior horsepower to weight ratio and relatively compact size.
Yanmar Yacht Engines
Yanmar has been a very reliable Japanese engine, popular with sailing yachts, trawlers, sport fishers and some motor yachts. Their mechanical 500 hp engine has been superb. They have recently merged with a little known (but excellent) Scandanavian manufacturer Scania to build a larger series of electronically controlled engines.
Volvo Yacht Engines
Volvo engines have been a long-time supplier of used yacht engines. Most recognizable are the 480 hp engine (noted for smokiness) and the 700 hp D12. Volvo has been pioneering the ‘pod’ technology for yachts, eliminating typical shaft driven/rudder systems.
These IPS (pod) engines are designed with the whole engine, transmission, exhaust and propellor as one unit, thus saving space for more interior volume.
These 660 hp units can be installed as 2 or more units next to each other that electronically turn as a synchronized system – or ‘fly by wire.’ The drives are designed to tear away without causing a hole in the hull in the event of grounding or hitting something hard.
Note that the cost of repairing pods in this event over direct drive is significant.
Cummins Yacht Engines
Cummins is also a big player in the yacht industry. Especially noted for high quality, reliable service, the Cummins 300-400 hp Diamond series and the QSM11 (660 hp) have been terrific engines.
Mercruiser and Cummins have partnered up to produce a pod diesel engine as well – known as the Zeus for multiple unit installations and rated at 715hp.
Diesel engines of lesser notoriety, but still found on yachts, are:
- Deutz (German)
- Sabre
- Perkins (British)
- Hino (Chinese)
- Ford Lehman (US)
- Lugger
- John Deere (US)
A special note: Engine manufacturers are being mandated to reduce emissions by way of exhaust filtration in the near future. This may drive up yacht costs or completely redesign engine room space for the extra systems required. Many yacht builders may end up going out of business if this becomes impractical!
