Expected life of yacht diesel engine and saildrive

[xyachtdave]

I think that hours are as important as years
My volvo MD2020 started life in 2003 & died in 2023 having clocked 5000 hours of excellent use. Only things -- alternator, Engine mount, saildrive seals, Exhaust elbows, starter relays, impellors plus fliters etc. No trouble with the saildrive other than shaft seals. Easy to do & I prefer it to shaft drive.
It was running like a sewing machine, then died suddenly, as if it had a heart attack, in less than 20 minutes, 25 miles offshore.
I now have a MD1 2030 (& new matching saildrive) which gives much better speed, but is a bit noisier in my 31 ft yacht
I spoke to Volspec who said that was a good life for one. They had seen them scrapped at 1500 hours due mainly to lack of use & maintenance

Interesting my MD2020a is 30 years old and currently runs like a sewing machine…

 

[Ammonite]

I tend to be very cynical when someone says "professionally maintained" in the context of yacht engines, as to me this means change the oil and filters every year and convince the owner to replace the engine when something significant goes wrong, hence the number of perfectly good second hand engines that end up with places like Marine Enterprises. Having said that if I had to pay a professional to overhaul the top end and heat exchanger of my 2500 hour MD2040 it would have probably made sense to replace the engine. As it is I now hope to get another 2500 hours out of it for a fraction of the cost.

 

[Moodysailor]

Many variables as others have pointed out, IMO most yacht engines would be replaced for reasons such as cost of repair or lack of parts before they wear out though use or hours. Sometimes the reason could be indirect - such as an engine that is no longer supported and trouble getting support/service vs a newer equivalent, or simply for comfort reasons (noise, fumes, etc).

 

[Laser310]

I have just been considering this, as I have gotten interested in a boat with 5000 hrs on the engines - it's a cat, so two of them.

the boat is only 6 or 7 years old, and I think they ran AC when at anchor.

So, this raises an issue which I haven't seen mentioned yet in the thread; the type of use, and whether it is within the envelope of recommended operation conditions.

Supposedly, diesel engines don't like to be operated at low loads, and I am guessing that running an AC would be pretty low load compared with motoring at say 7kts.

I am wondering how much I can learn from having a diesel mechanic do an engine-specific survey.

 

[Supertramp]

I have just been considering this, as I have gotten interested in a boat with 5000 hrs on the engines - it's a cat, so two of them.

the boat is only 6 or 7 years old, and I think they ran AC when at anchor.

So, this raises an issue which I haven't seen mentioned yet in the thread; the type of use, and whether it is within the envelope of recommended operation conditions.

Supposedly, diesel engines don't like to be operated at low loads, and I am guessing that running an AC would be pretty low load compared with motoring at say 7kts.

I am wondering how much I can learn from having a diesel mechanic do an engine-specific survey.

That is a huge number of hours for 6-7 years. And if you are right about air conditioning, why run 2 engines? It sounds more like a boat used for trips/charter - worth finding out.

I would start by looking at 5000 hours of service and repair records! And checking for leaks etc.

As many others have said, it's less to do with hours and more to do with regular servicing, inspection and repair. And how it's been used - one owner gently or multiple users roughly.

Which I think is the point you were raising.

 

[Tranona]

I have just been considering this, as I have gotten interested in a boat with 5000 hrs on the engines - it's a cat, so two of them.

the boat is only 6 or 7 years old, and I think they ran AC when at anchor.

So, this raises an issue which I haven't seen mentioned yet in the thread; the type of use, and whether it is within the envelope of recommended operation conditions.

Supposedly, diesel engines don't like to be operated at low loads, and I am guessing that running an AC would be pretty low load compared with motoring at say 7kts.

I am wondering how much I can learn from having a diesel mechanic do an engine-specific survey.

Sounds like they might be hybrids. Running anything that needs the power that AC does will load the engines OK. The light load running is usually related to using the engine to charge batteries using only the alternator which puts virtually no load on the engine. Likewise using the engine to boost speed under sail in light wind (motorsailing) may not load the engine. One of the benefits of an Autoprop is that in motorsailing the pitch is adjusted to load the engine.

5000 hours is about half life for the oily bits of the engine. It is the cooling system and electrics that may have shorter lives unless preventative maintenance is applied.

 

[Moodysailor]

I have just been considering this, as I have gotten interested in a boat with 5000 hrs on the engines - it's a cat, so two of them.

the boat is only 6 or 7 years old, and I think they ran AC when at anchor.

So, this raises an issue which I haven't seen mentioned yet in the thread; the type of use, and whether it is within the envelope of recommended operation conditions.

Supposedly, diesel engines don't like to be operated at low loads, and I am guessing that running an AC would be pretty low load compared with motoring at say 7kts.

I am wondering how much I can learn from having a diesel mechanic do an engine-specific survey.

There is a long answer to this, i'll try to summarise.
It is correct that light-loading a diesel engine is bad for it long-term. It is also correct that hours is an important, but not the only factor to consider when assessing a marine engine.
The engine can suffer from light load in a number of ways- incomplete combustion (carbon build up), bore glazing (smoke) and diesel wash (oil dilution).
If you are concerned then a thorough inspection including having an oil analysis done and a sea trial where you starts the engines from cold and run them through a variety of rpm and load including full temp and full load to check for smoke. The next step is to have a bore-scope (camera) inspection done, but it is unlikley that this will be allowed pre-purchase due to the need to do some engine work (pull the injectors).
I have seen engines that were so bad the only remedy was to hone the bores, but those were much bigger engines.
In short, I would approach with caution but have a trusted engineer do a really good check and go on a sea trial. Don't let your heart rule your head.

 

[Boathook]

Has anyone noticed that practically all the kit mentioned above isn't modern...

E.g. My 4.108 was forty this year. About 3000 hours, so equivalent of about 150,000 miles use by a steady white van driver. I expect it to outlast me. Though heat exchangers can be considered service items, and I will get around to fitting the 'modern' rear crankshaft rope seal before engine oil becomes scarce.

I replaced the engine & turbos in my ten year old VW at 120,000 miles... "That one lasted well sir!"

My golf (diesel tdi) had 185K miles and still ran well. Didn't use oil. Sold it to my niece for a nominal amount and it is still running.

 

[SaltyC]

It all depends on use. Marine engines tend to be lightly stressed and running at constant revs, unlike car engines started from cold, revved hard then shut down.
My normal engine hours are 50 to 75 per year (it's a SAILING boat) at the end of the season. The oil on the dipstick is clean enough to be difficult to detect.
This year I have done quite a lot of engine work for me (130 hrs to date) the oil on the dipstick is coloured but not black!

I 'killed ' my MD2020 in the last boat! Due to health problems the only use it git was club racing, start motor around marina, into sea lock tickover, leave sealick and harbour put sails up stop engine. Returning similar scenario, never running at 2000rpm and never getting really hot . The following season exhaust elbow blocked £400 for replacement.

How you ascertain tge use and maintenance on a secondhand boat i do not know.

 

[RunAgroundHard]

I can't comment on overall engine age and replacement strategy, but I am aware that an insurance company refused to cover damage to an engine due to failure of a mount. The insurance company expected the mounts to be replaced at 10 years, and these were older. I don't know who the insurance company is, information was from pontoon neighbour who experienced the failure and had to foot the bill himself.

Anyway the point is, while the older engine may be good, there may be other age related factors that you need to consider.

 

[Martin&Rene]

An engineer who has done some work on my yacht over the winter has said that a problem on many yacht engines is that you have to pump out the oil through the dipstick hole. You normally do not get out all the old oil and this can cause problems over a long period of time. His recommendation is that having drained the oil, put oil in to the minimum level, run it for a short time to flush the engine, then empty, change oil filters and refill.

 

[Moodysailor]

An engineer who has done some work on my yacht over the winter has said that a problem on many yacht engines is that you have to pump out the oil through the dipstick hole. You normally do not get out all the old oil and this can cause problems over a long period of time. His recommendation is that having drained the oil, put oil in to the minimum level, run it for a short time to flush the engine, then empty, change oil filters and refill.

This is something i've heard repeated many times during my career. I have worked for engine manufacturers that did some analysis on this - whilst it's correct in theory, the reality is that the amount left is negligable and has little, if any impact. What they did find in favour of this method is that engines that have oil drained via the bottom of the engine directly were less likely to have the engines run prior to an oil change, whereas engines that have the oil drained via a pump out tube often are run (to warm the oil thin enough to flow easily). Running the engine is better in the long run as contaminents are suspended in the oil and then get removed when it's sucked out. If the engine hasn't been run, contaminents can settle, remain in the bottom of the sump and don't drain out.

All of this assumes some fairly controlled environments and assumptions that service intervals are rigorously maintained. I should also state that some small engines (e.g Volvo Penta) have dedicated oil suction tubes that go to the bottom of the sump and have a better chance of extracting more oil than your standard dipstick tube.

On a slightly related topic, they also found that oil is best filled into the sump directly rather than the rocker box. This is so that any possible contaminants go into the sump and therefore the oil filter rather than the rotating parts of the engine. This is why some (not all) engines have fillers directly into the lower part of the engine. As an engineer, I found it interesting

 

[Daydream believer]

On a slightly related topic, they also found that oil is best filled into the sump directly rather than the rocker box. This is so that any possible contaminants go into the sump and therefore the oil filter rather than the rotating parts of the engine. This is why some (not all) engines have fillers directly into the lower part of the engine. As an engineer, I found it interesting

Interesting that on my new Volvo D1-30 there are 2 filler points. One being nearer the sump.
When I used to service our family plant- Petters, Lister diesels etc. in dumpers, mixers, hoists etc. I often ran some Castrol Flushing Oil through them & drained from the sump. It definitely dragged some extra debris with it.

 

[Ammonite]

An engineer who has done some work on my yacht over the winter has said that a problem on many yacht engines is that you have to pump out the oil through the dipstick hole. You normally do not get out all the old oil and this can cause problems over a long period of time. His recommendation is that having drained the oil, put oil in to the minimum level, run it for a short time to flush the engine, then empty, change oil filters and refill.

Everything else being equal I suspect there's some truth in that but the average yacht engine does a fraction of the hours the same engine does in a tractor, dump truck etc so there will be far more contaminants being circulated around the latter on average than in a yacht engine, even if you leave a little bit behind each year. Lack of use, not being run under load and damp / rust etc is a far bigger issue