Expected life of yacht diesel engine and saildrive

[dunedin]

What do we think is the typical expected usable lifespan of a modern yacht diesel engine and associated saildrive?

I know that there is no definitive answer - like Trigger's broom, whilst parts and skilled DIY labour are available, a diesel engine can go on almost indefinitely.

But when do folks typically call time and go for a replacement? And does a modern saildrive last as long as the associated engine?

NB Talking about RCD/RCR compliant engines available to buy today, not older types from 50 years ago

 

[ylop]

Are your 5 yr windows not too tight for something which actually is going to depend a lot on use? A boat that is in charter / school use every week for 26 weeks a year gets a different set of wear from one that is used every second weekend and for a fortnight holiday. One on live aboard cruiser might see very different use again, and that probably depends if its being used for power / hot water or if solar/genny are covering those. Hopefully the different uses = extra maintenance but every owner is different. I think if it was <30yrs I'd be disappointed, but when we were buying we set ourselves a limit that anything with an engine older that that we would budget for potentially replacing.

 

[Bodach na mara]

I would expect an engine of that era to be still usable after 40 to 50 years or longer. Most of them get used for around 100 hours per year so 50 years would equate to 5000 hours. I assume that regular servicing and changing of fluids would occur. Ancillary equipment such as starter, generator and pumps would possibly fail and need repair or replacement but the core engine should be in reasonable nick after 5000 hours. Certainly my farmer friends reckon on doing about 500 hours a year in tractors and regard a 10 year old tractor as good for another 10 with a good service. Personally, I have had three boats with diesel engines and the actual results were mixed. The first (BMC Captain 1500 cc installed in 1965) was still on its first engine when I last saw it in 2000. The second (modified Ford by Watermota 1200 installed in 1974) was replaced in 2010, but the problem was not the engine, but the gearbox, and it would have been possible to just rebuild the box. The third is my current boat (Volvo Penta 2003 installed in 1985) failed in 2018. It was a trivial fault in my estimation, I big leak of oil from the rear crankshaft seal. But both engineers that I consulted required the engine and gearbox removed before they could start locating the fault and the difference in the quotes for the repair (assuming that I was correct) and replacement with a new engine and gearbox was just over £1000. I went for the piece of mind and possible increased sale value of the new engine.

I have no views on saildrive lifespan as I wouldn't touch one with a barge pole.

 

[SaltyC]

It all depends on hours usage and treatment / maintenance.

Marine engines have an 'easy' life. Constant revs no stress.

They do however need regular maintenance and oil changes.

The biggest problem is lack of use (Hours).

 

[Iliade]

Depends how damp the boat is, how well the motor is used, and whether there are any stray (electrical) currents lurking.

Boat engines very rarely get worn out, they tend to get corroded and clogged long before then.

Most modern kit (of all types) is not designed to outlast the warranty by very long at all...

 

[geem]

We don't have a saildrive but the prop shaft is original, now 45 years old. The engine was replaced at 27 years. The 'new' one is 18 years old and like new. 3000 hrs so far but it is a low revving Perkins and 4.4L

 

[Supertramp]

As others have said, maintenance is everything. Regular changing of filters and fluids plus checking for any signs of a developing problem. I remember talking to an engineer at work where we ran electric generators and there were many over 50 years old, one with 170,000 hours. He used a stethoscope to assess the bearings! But they did have strip, repair and rebuilds every 30-50,000 hours. They also ran at low speeds, none of this Italian tune-up stuff. No-one still does that!

The main issue with yacht engines is the marinisation, including gearboxes (or saildrives). There seems to be something on most makes that decays or fails over time due to poor design, mixed metals or wear and tear. Its usually fixable but as in post #3 many will understandably choose replacement rather than repair.

The original Volvo D55 on my boat lasted only 19 years and 2650 hours. I don't know what went wrong. It now has an 18 year old Beta 60 which is a joy but has needed some wiring replaced and has corrosion starting of mixed metals in the heat exchanger. I flush the system with fresh water when leaving the boat for several weeks, and use old antifreeze to winterise the raw water system.

The answer to the question posed depends how you use and maintain it. The most important thing with yacht engines is having total reliability and dependability. Used carefully, maintained thoroughly and repaired if something fails, then I think over 50 years is easily achieved, with the caveat that at that age there are "core" components like oil and water pumps, starter motors and oil seals that may need age related attention.

I don't know about saildrives - they may be a bit like Beta heat exchangers......

 

[bitbaltic]

I voted 41-50 years because my MD2020 is now 24 years old and no way can I afford to replace it so it has to last at least that long.

Seriously though, it does tiny miles and is annually serviced professionally. I also try to be proactive eg changed the elbow at 20 years, not because there was anything amiss just an upgrade to stainless for longevity. Parts are still okay for it so I hope it goes a long time yet.

Saildrive is a Volvo 120, never any issues with it except some seals replaced this season. Same thing, tiny miles and professional annual maintenance. Fingers kept crossed

 

[Daydream believer]

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

 

[Buck Turgidson]

Well mine is 46 so I'm hoping well over 50 years.

 

[geem]

My Perkins 5kw twin cylinder diesel generator is 30 years old. It's not done many hours as we don't use it much. It has needed a fresh water cooling pump and it continually wears out raw water pumps (I keep 3 spares) but it is a super simple bit of kit with no electronics. I am hoping it will go for another 10 years. It's a high reving 3000rpm unit but only has 2600 hours on it

 

[obmij]

When parts are no longer available.

I would also measure lifespan / maintenence in terms of engine hours rather than time elapsed.

 

[Iliade]

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!"

 

[geem]

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!"

I got rid of my sugar legacy 2.5L petrol at 175,000 miles. It was still running well and trouble free.

 

[Stemar]

While the lifespan and reliability of car engines has increased enormously in the last 50 years, I suspect that the opposite is likely to be true for marine engines, yacht engines in particular. Adding clever electronics may give more power and efficiency, but a damp, salty environment plays hell with electronics unless they're specifically designed for the environment. I confess I've no idea how much electronics a modern yacht engine has but, were I shopping for one, mechanical everything would definitely get my vote, and the ability to tinker with the control panel when (not if, judging by these forums) it goes wrong would be a definite bonus.

 

[[194497]]

The problem is, we won't know how well today's new engines will last for a few decades yet - all the data we have about long engine life is going to be about old ones!

 

[Blueboatman]

I’ve enjoyed an older petrol and diesel that after a good 50 years and 40 years respectively were inherently so simple that I felt age would not change them

But of course the philosophy @ time of manufacture was understandably different. If you’re going to go to all the trouble of building an expensive marine engine using scarce expensive materials why build it to wear out?

Equally I wonder if Daydream Believer did an autopsy on his dead Volvo?

Why would a modern engine with oil and coolant self destruct running at operating temperature at steady rpm without warning?

 

[Stemar]

Why would a modern engine with oil and coolant self destruct running at operating temperature at steady rpm without warning?

It shouldn't, but if it's built to a budget rather than a quality, unexpected things can be expected sooner or later.

 

[Malish]

I would like to know what the replacement target is for engine manufacturers ... probably too small a market to bother with. but it is possible that as designs become more advanced (? impacted by the regulatory environment ?) then redudancy due to non-availability of key bespoke parts may become the norm.

 

[LittleSister]

Most small 'auxiliary' yacht engines these days are based on Asian industrial engines produced in huge quantities and generally used in construction plant, generators, etc. (where they can expect a hard life and to last a lot of hours). I imagine that they are machined to finer tolerances compared to early auxiliary engines and benefit from more advanced engineering. The ones I am familiar with do not have complex electronics (I imagine that is more the preserve of larger engines for mobos). I imagine they will last very well in terms of wear and reliability compared to their predecessors, assuming diligent maintenance.

If you want an old school engine, Bukh still make ye olde DV24 (and DV29 and DV32 variants) and the DV36 (first produced 1979, and with DV48 variant) alongside more modern much larger workboat engines, but they are expensive and very heavy compared to modern alternatives, so rarely fitted from new in yachts these days, but the standard fitment for lifeboats.

As others have said, it is the peripherals and marinisation bits that tend to give the most trouble as 'auxiliary' engines age, but these rarely spell the end of the motor's life in themselves. That seems to come when there is either a major failure inside the engine, or widespread cumulative wear.

I think it is increasingly the practice to replace rather than rebuild engines that have major faults or widespread wear issues. I guess that is at least in part due to the high cost of engineers and parts to do such work, compared to the relatively low cost these days of manufacture/purchase of a new engine.