Engines: Old and easy to repair vs New and reliable.

[GoneDiving]

I'm at the very early planning stages of looking for a sub-50ft offshore cruiser/dive vessel and am becoming more and more impressed with converted Cray/Lobster trawlers as an option to allow me to island hop and, as skills and experience improve, head to remote areas of PNG, Marshall Islands etc.

Drive power in used vessels tend to fall into two categories: newer, more efficient and reliable but more technical to maintain engines and older, thirstier but dead simple ones. Older engines also seem to be far less "sexy" and significantly depress asking prices.

As extremes, if I look at a Detroit 671 vs a Yanmar 4LV producing 100 shaft hp, the 671 will use ~30% more fuel, at near half the revs, a bunch more noise but has a life expectancy of forever, user replaceable parts and servicing at comapratively very low prices.

I'm fairly mechanically minded so am leaning towards the old and simple so that I can repair faults whenever and wherever they may occur. Most likely a middle ground of Gardiner or Ford Lees/Lehman.

What are others preferences for remote and/or passage making vessels? What have I missed?

Many thanks

[Pizzazz]

Just get the Yanmar.

[GoneDiving]

Originally Posted by Pizzazz

Just get the Yanmar.

Thanks for that very informative reply. 😁

[Dsanduril]

I’m with you on the simpler engine, but the Marshalls are a long way from anywhere. 30% difference in fuel could make all the difference in being able to get there. Which would leave me asking the same question as you. Gut feeling, if I truly wanted to go that far afield is that fuel economy would win.

[jimbunyard]

Certainly wouldn't go with any Yanmar, but that's just my personal preference.

Any electronically-controlled engine has reliability issues in the marine environment; in remote areas this is doubly problematic.

There is much to recommend full mechanical injection systems, overhead valves, and simpler induction methods (no turbos or inter/aftercoolers); they're typically more field-servicable and easily diagnosed if trouble occurs.

On-board spare parts inventory is generally lower, an added bonus of reduced complexity.

Speaking of extremes, the 6-71 is certainly thirstier; perhaps it's long life and near-ubiquitous parts availability offset that downside substantially.

I looked for parts for a 4LV150 Yanmar, and even though I could find part numbers, I could find no prices or stock availability from anyone at all. Which means you have to buy from the Yanmar monoply. Which means they charge what they want.

Of course there are plenty of options between the archaic and ultra-modern. The Gardner or Lehman are good choices, but there are many others. Most any diesel from between 1985 and 2010 will have the desired characteristics of simplicity, long life and reasonable efficiency; a little homework will refine your ability to make a selection that best fits your requirements.

Personally, I like Kubota-based engines, though. if it weren't for their prices and confounded electrical systems. some of Volvo's in-house and rebranded engines would be a close second...

[Simi 60]

Originally Posted by GoneDiving

Drive power in used vessels tend to fall into two categories: newer, more
As extremes, if I look at a Detroit 671 vs a Yanmar 4LV producing 100 shaft hp, the 671 will use ~30% more fuel, at near half the revs, a bunch more noise but has a life expectancy of forever, user replaceable parts and servicing at comapratively very low prices.

Why so limited?
855 Cummins is a very popular engine in the industry for a reason.
Totally mechanical, quiet, economical, parts everywhere.

Guessing by destination and intended use that you'll be looking at 50+ foot vessels.

[Dennis.G]

New and reliable. If looking at 100 hp plus will likely be turbo but not to be afraid of. About every big truck running thousands of hours yearly do so with turbos. Other than that new diesels are not much more complicated, just built better to closer tolerances.

A new well maintained diesel engine will likely outlive you. An old school engine might be easier to work on, but you will need to work on it. If you don't have the parts with you, likely easier to get parts for a newer engine delivered than trying to source parts for an old engine. Yanmar for example has distributers all over the world, and where they are not you can have stuff shipped from stock. Also remember 20% fuel savings will add up to big money quick, and 20% fuel savings equals 20% increase in cruising range.

If it comes down to budget and you can only afford old school, then keep reminding yourself that you have something easier to fix when it breaks.

BTW, I put up with old stuff all the time.

Oh, I just re-powered with a Kubota (Beta Marine) last year. I am not familiar with new Yanmar but the Kubota is quite simple in my opinion.

[GoneDiving]

Originally Posted by Dsanduril

I’m with you on the simpler engine, but the Marshalls are a long way from anywhere. 30% difference in fuel could make all the difference in being able to get there. Which would leave me asking the same question as you. Gut feeling, if I truly wanted to go that far afield is that fuel economy would win.

Thanks for that. I used the 671 as the extreme simplicity case. They have a lot going for them but I'd agree that for any significant range they add alot of fuel requirements both in terms of $$$ and tankage. Unfortunately it just gets worse as trip and ownership time gets longer.

[Simi 60]

Originally Posted by Dennis.G

An old school engine might be easier to work on, but you will need to work on it. If you don't have the parts with you, likely easier to get parts for a newer engine delivered than trying to source parts for an old engine.

As someone living aboard cruising full time with an older style engine I disagree at least with our engine.
In frame rebuild interval is around 30,000 hours....thats near 75 years away.

4 years out here as a primary source of propulsion and its only the cooling circuit and oil that has needed attention, same as on any boat.

Parts are very easy to buy from Cummins China for a fraction of the price of Cummins Australia and arrive in under a week.

[GoneDiving]

Originally Posted by jimbunyard

Of course there are plenty of options between the archaic and ultra-modern. The Gardner or Lehman are good choices, but there are many others. Most any diesel from between 1985 and 2010 will have the desired characteristics of simplicity, long life and reasonable efficiency; a little homework will refine your ability to make a selection that best fits your requirements.

Personally, I like Kubota-based engines, though. if it weren't for their prices and confounded electrical systems. some of Volvo's in-house and rebranded engines would be a close second...

Yes there are lots of options should I choose a full repower. Not sexy, but throughout Asia, marinised and derated light truck engines are very popular. They have the benefit of parts and skills being available everywhere. There must be a million Hino, Nissan, or Mitsubishi 7t trucks rolling around the region. 😀

I think I would prefer a simple OEM marine engine though.

Thanks

[GoneDiving]

Originally Posted by Simi 60

Why so limited?
855 Cummins is a very popular engine in the industry for a reason.
Totally mechanical, quiet, economical, parts everywhere.

Guessing by destination and intended use that you'll be looking at 50+ foot vessels.

At this stage I'm not limiting my options. I just used the 671 and Yanmar as the extremes and Gardiner as mid field. I'd agree that there are many options for a repower, especially in that mid field.

I'm also keen to get a feeling for what is attractive or to be avoided as I look at vessels that are a going concern. I'm happy to personalize and customize but I'm not looking for a bespoke project boat.

Thanks

[GoneDiving]

Originally Posted by Dennis.G

A new well maintained diesel engine will likely outlive you. An old school engine might be easier to work on, but you will need to work on it.

Originally Posted by Simi 60

As someone living aboard cruising full time with an older style engine I disagree at least with our engine.
In frame rebuild interval is around 30,000 hours....thats near 75 years away.

4 years out here as a primary source of propulsion and its only the cooling circuit and oil that has needed attention, same as on any boat.

Parts are very easy to buy from Cummins China for a fraction of the price of Cummins Australia and arrive in under a week.

The trick is to pick the model on the tipping point where it's simple enough to be reliable and easy to repair but not so old that its constantly in need of those simple repairs

Thanks

[Tillsbury]

The difficulty is finding an older engine that you know hasn't been abused too much. I'd be all in for a twenty-year-old engine that's been well maintained, but if the history is dubious then any engine can be trouble.

[GoneDiving]

Originally Posted by Simi 60

Guessing by destination and intended use that you'll be looking at 50+ foot vessels.

Not totally decided yet. But 50ft seems to be the step change for complexity and cost. As I want to be able to single hand at times where appropriate and not rely on crew, at this stage I'm looking at high 40's.


Cheers

[GoneDiving]

Originally Posted by Tillsbury

The difficulty is finding an older engine that you know hasn't been abused too much. I'd be all in for a twenty-year-old engine that's been well maintained, but if the history is dubious then any engine can be trouble.

True. There is 'old', 'old style' and 'worn out'.

If much prefer a 20 yo engine that has been well cared for vs a 5 yo that only saw oil when alarms went off.

The simpler models can be very easy and cheap to freshen up. I can see merit in paying $10k to get a engine that will last my lifetime.

Cheers