Why do people replace diesel engines in a sailboat?

[a64pilot]

There are a few reasons for a cylinder wall to become smooth so that oil isn’t contained in the cross hatching and blowby goes up, oil temp goes up, oil gets black quickly and oil consumption increases.
First is cylinder wall glazing, that is actually unburned fuel deposits coat the cylinder walls and eventually turn into something like a varnish.
It’s from low temp operation, if the engine is allowed to run at design temp this won’t happen, it takes very little load to get up to operating temp, but loads just from an alternator if using the engine to charge batteries is often not enough load.
Often unless allowed to get really excessive glazing can be recovered from, by a good detergent in the oil and an Italian tune up.
I’ve never seen it so bad that the engine has to be honed myself, heard of it, but never seen it.

Second is bore polishing, something that airplanes that are infrequently used and our boats suffer from as they age. An engine that sits for a decent long interval, say weeks can and will form a light coat of rust on the cylinders, especially if it has water in the exhaust as that is a humid environment.
When the engine is started of course this rust is very quickly cleaned off by the piston rings, but it causes wear of the cross hatching, repeat dozens or hundreds of times and eventually you have polished your bores.
Bore polishing the only cure is either honing, or usually bore it out to oversize as likely the engine is decades old anyway.

However these engines can have excellent crankshafts and cams, lifters etc. that exhibit very little wear, they are mostly victims of just not being used, and are often excellent candidates for an overhaul

I plan on keeping my old 4JH(B)E until lack of parts force me to replace it, I think your crazy to not overhaul an engine that still has good parts availability, a good overhaul is Better than new, cause you determine the tolerances in an overhaul, the engine can be as perfect as you can make it if you desire.

[olaf hart]

Originally Posted by a64pilot

All internal combustion engines I am aware of have some form of crankcase vent.
However PCV stands for positive crankcase ventilation, a Diesel has no vacuum so unless a pump has been fitted for this purpose it can’t be a positive crankcase vent, that is on gas engines that have vacuum, the vacuum in the intake manifold is what makes it a positive crankcase vent.
Trivia really the result is the same, but hopefully the manual doesn’t refer to it as a PCV system does it?

No, it’s just a crankcase vent, it is built inside the rocker cover and goes to an inlet port opening into the rocker area.
There is apparently some some wire mesh filter as well, I will check it out when I do the valve clearances.

[a64pilot]

Originally Posted by olaf hart

No, it’s just a crankcase vent, it is built inside the rocker cover and goes to an inlet port opening into the rocker area.

There is apparently some some wire mesh filter as well, I will check it out when I do the valve clearances.

What you describe is extremely common, even among automobiles.
The mesh serves as an air oil separator, and sometimes if oil changes are neglected and or cheap oil used the valve cover being cooler than the rest of the engine the oil fumes will condense to a wax like substance and can clog that mesh, then you build crankcase pressure and start blowing seals or maybe leaks.
When the valve cover is off, look for this issue, usually mineral spirits will clean it out pretty well.

[u4ea32]

I spent a lot of money and time refurbishing a low hour Yanmar 3GM30F. The result was rude: noise, vibration, smell, complexity, expense, maintenance, and an absurdly low level of reliability. I did not want to continue to be abused by something that is essentially unnecessary.

So I pulled it all out, and went electric. A Tesla of the Seas.

ElectricYacht 10KW air cooled (more than twice the power I need), with a 5KW bank of LiFePO4 GC2 batteries by Battle Born in Reno.

It is not a little better. It is enormously better in every single way.

[BoatandBeach]

Originally Posted by u4ea32

I spent a lot of money and time refurbishing a low hour Yanmar 3GM30F. The result was rude: noise, vibration, smell, complexity, expense, maintenance, and an absurdly low level of reliability. I did not want to continue to be abused by something that is essentially unnecessary.

So I pulled it all out, and went electric. A Tesla of the Seas.

ElectricYacht 10KW air cooled (more than twice the power I need), with a 5KW bank of LiFePO4 GC2 batteries by Battle Born in Reno.

It is not a little better. It is enormously better in every single way.

Until you need more than a very modest range motoring. Otherwise I'm with you. But we're still at least a decade (probably closer to 2) from seeing battery/electric tech replacing diesel for the average consumer.

[newhaul]

Originally Posted by BoatandBeach

Until you need more than a very modest range motoring. Otherwise I'm with you. But we're still at least a decade (probably closer to 2) from seeing battery/electric tech replacing diesel for the average consumer.

you mean like the run thru the red sea after the Suez canal as recommended to avoid possible piracy issues for 24 to 36 hours straight on a circumnavigation or just a transit from the med to the Indian.

Or bashing north to san Diego from Mexico

[malbert73]

Originally Posted by newhaul

you mean like the run thru the red sea after the Suez canal as recommended to avoid possible piracy issues for 24 to 36 hours straight on a circumnavigation or just a transit from the med to the Indian.

Or bashing north to san Diego from Mexico

Or even like trying to get to a reasonable destination on the Chesapeake in the summer when the breeze doesn’t materialize? 30nm at 7 kts can’t be done with any reasonable array

Mike

[mikedefieslife]

Originally Posted by malbert73

Or even like trying to get to a reasonable destination on the Chesapeake in the summer when the breeze doesn’t materialize? 30nm at 7 kts can’t be done with any reasonable array

Mike

All this might be true but why do people even bother with the argument when they know damn well that some people sail in their local areas, or even around the world without an engine. Rather than trying to educate it instead reads as pushing an agenda.

---

Now on the subject of repowering. It's a strange one. How many people repower their cars, motorcycles, campervans? I don't imagine many. That being said, I can certainly understand it. Especially if you are buying an old boat. The engine installed might have an unknown installation date, unknown hours, unknown service histroy, and you've got no idea what the mods and bodges the previous owner(s) have done. In such cases often it's not even worth time to figure it out. It usually takes much longer to deconstruct something and rebuild, than to just build or start from a clean slate.

[Rorzech]

Here's another reason. I just pulled my Atomic 4 Gas engine out and dropped a diesel right into the same spot. I got the boat for nothing because the gas engine wouldn't run and I don't like the constant danger gasoline brings to the table. The boat was well worth the new diesel.

[newhaul]

Originally Posted by Rorzech

Here's another reason. I just pulled my Atomic 4 Gas engine out and dropped a diesel right into the same spot. I got the boat for nothing because the gas engine wouldn't run and I don't like the constant danger gasoline brings to the table. The boat was well worth the new diesel.

where are you located? I could use that a4 as a parts motor

[Rorzech]

Yes reliability and piece of mind is valuable. A couple of days ago a giant cruise ship in Venice came crashing into the dock and smashed a tour boat and injured some people, all because he developed a problem with his engine. The captain was on the bridge watching the slomotion disaster helplessly. Yes reliability is paramount !

[Rorzech]

Thunder Bay Canada. rjzech@gmail.com

[Island Time O25]

A good buddy who happens to be a diesel mechanic for past 45+ years swears by keeping old school heavy and slow turning diesels over shiny new electronics ladden thin walled ones. Says old Yanmars way more reliable then the latest generation. Same for Kubota based Universals. Also he's very down on modern Volvo diesels, especially their overpriced parts and often less then competent service departments.

Also the old school engines are easier to service in out of the way places, having no or little electronic parts, etc. If you're repowering a day sailer in New England or PNW it's not an issue but if you're far from civilization on RTW chances are that a local mcgyver can bring an old Perkins or Universal to life more easily with cannibalized parts and whatnot than a commonrail latest turbo engine.

[newhaul]

Originally Posted by Rorzech

Thunder Bay Canada. rjzech@gmail.com

wrong coast darn it . Not worth the cost of shipping

[Jimmyhenry]

Love my Perkins 4-236. 5000 hours, 43 years old. Purrs. and powerful.

I bought a "spare" one ($NZ3.000) just in case as my partner was worried about the old one. Still got in in the garage under covers.

Had to motor back from Tonga last year, no wind. Six days on motor.

Pete