Perkins 4.108 - Rebuild or ???

[malbert73]

Originally Posted by gcaws

I had a diesel mechanic rebuild my 4-108 and it worked for a time. Unfortunately it stated leaking oil and the older unreplaced parts started breaking down. I realise you’re doing the work yourself but it created huge problems in terms of reliability and a huge oil-in-bilge mess that I still deal with today. I then bought a drop in replacement Beta Marine BV2203 (Basically a 50 hp Kubota tractor engine that is marinized in England) and have been thrilled (yes thrilled). After over 10 years it has proven hyper reliable and not fussy. It was not expensive and I should have just purchased it rather than just continue using the 4-108. Please investigate as it may change what you do.

Yes- Morgan’s cloud cited a stat that vast majority of folks who do rebuilds end up repowering within 2-3 years
Problem with rebuilds is that EVERY part on the engine is X hours and Y years old, and you can get a cascade of tiny, annoying failures. New can be better in many ways, though price is somewhat higher up front (but perhaps better in long run)
No reason but cost that I can see keeping an old Perkins instead of a new Beta. My 50 is based on a Kubota V2203 that is flogged and keeps running in so many pieces of industrial equipment and I can order cheap kubota brand filters for these tractor engines on amazon.
Funny the Bobcat 773 in my marina has same engine in it and has been chugging along for seemingly decades

[Algee]

Do a compression test, that will give you an indication to the state of the liners and rings.

[mvweebles]

Originally Posted by malbert73

Yes- Morgan’s cloud cited a stat that vast majority of folks who do rebuilds end up repowering within 2-3 years
Problem with rebuilds is that EVERY part on the engine is X hours and Y years old, and you can get a cascade of tiny, annoying failures. New can be better in many ways, though price is somewhat higher up front (but perhaps better in long run)
No reason but cost that I can see keeping an old Perkins instead of a new Beta. My 50 is based on a Kubota V2203 that is flogged and keeps running in so many pieces of industrial equipment and I can order cheap kubota brand filters for these tractor engines on amazon.
Funny the Bobcat 773 in my marina has same engine in it and has been chugging along for seemingly decades

Vast majority who rebuild end up repowering? Statement gets 4 Pinocchios for the day. Nothing could be further from the truth. Many OTR trucks get millions of miles with a few rebuilds. Many commercial vessels get rebuilds after 20k hrs or more and go another 20k hrs.

This is a categorically incorrect statement. Some rebuilds may be haphazard, but statement is way to sweeping to be anywhere near truthful.

Sorry. Calling BS on this one.

Peter

[Frederic64]

I have a belt driven water pump">raw water pump on my perkins4108, it’s easier to service and maintain and cheaper in parts. I can replace the impeller under half an hour if it’s damage.
I had to add an extra pulley aswell, the engine is simple, hasn’t got any electronic, no turbo, it’s a working engine, cast iron, easy to work on and still plenty of spare parts. The only issues I had is that not all perkins4108 have exactly the same parts, there slight differences in parts, ie glow plugs for example. If you think the engine is ok and can do the work yourself then I would do it. Use this opportunity to check snd change the engine mounts aswell.
If you go different engine then there are more issues to consider such as length, coupling to drive shaft, higher etc....

[gcaws]

Originally Posted by mvweebles

Vast majority who rebuild end up repowering? Statement gets 4 Pinocchios for the day. Nothing could be further from the truth. Many OTR trucks get millions of miles with a few rebuilds. Many commercial vessels get rebuilds after 20k hrs or more and go another 20k hrs.

This is a categorically incorrect statement. Some rebuilds may be haphazard, but statement is way to sweeping to be anywhere near truthful.

Sorry. Calling BS on this one.

Peter

Thank-you for your opinion. And thank you for reminding me of positive social skills in these trying times. All situations are different and one persons experience will be different than another.

[gulfislandfred]

A belt driven raw water pump would be a great improvement! Do it if you can.


You should be able to drive your alternator and raw water pump with one belt, if you have room to get enough angle so there's good belt contact. I've had a couple of OI 41s, and I seem to remember that the engine space is not too cramped.



I think you can get the whole new sleeve with new piston and connecting rod as a drop in, if you want to do the rebuild while the engine is out. No Idea of price.

[Icarus]

Check compression, I would pull the head off and get it serviced,..but that's me.
if it runs ok at least replace the seals.
Perkins engine seem to be prone to cylinder bore ridges.

[malbert73]

Originally Posted by mvweebles

Vast majority who rebuild end up repowering? Statement gets 4 Pinocchios for the day. Nothing could be further from the truth. Many OTR trucks get millions of miles with a few rebuilds. Many commercial vessels get rebuilds after 20k hrs or more and go another 20k hrs.

This is a categorically incorrect statement. Some rebuilds may be haphazard, but statement is way to sweeping to be anywhere near truthful.

Sorry. Calling BS on this one.

Peter

Ok, well then.

This is a thread about sailboat engines, not truck diesels, right?

I went back to the Morgans Cloud site to make sure my “facts” are straight and John cites 12 small diesel rebuilds in sailboats he had direct knowledge of, mostly yanmars and westerbekes.
2/3 of those were subsequently repowered within 2-3 years, some within months. So they paid twice.
The conclusion is think carefully about whether it’s worth rebuilding, since EVERY component is old- and many repowers only focus on the cylinders/etc. so add injector pump, transmission, mounts, etc etc.

I imagine the difference in industrial and truck applications is that truck diesels are rebuilt on a schedule and aren’t subject to low load, long periods of lack of use, and salt water.
I think many sailboat engines are rebuilt when they are unreliable or not running well.

But with a great underlying engine- 4108 is one, I bet it could be worth it. But saying “they don’t make em like they used to” is only true if you consider the opposite- new ones are better- if you choose a mechanical, industrial based engine like a Kubota/Beta/etc.

My 2 cents. I could have rebuilt my old yanmar 4jhe and I’d still have an engine with max HP at 3600, with a smoky exhaust due to primitive fuel injector technology, with a 33 year old transmission, etc. And could have had to slowly pour more money (and worry) into it.
The slower revving Beta 50 is superior in every way. Upfront more costs but now I can enjoy a completely reliable, warranty covered engine.

[malbert73]

Originally Posted by mvweebles

Vast majority who rebuild end up repowering? Statement gets 4 Pinocchios for the day. Nothing could be further from the truth. Many OTR trucks get millions of miles with a few rebuilds. Many commercial vessels get rebuilds after 20k hrs or more and go another 20k hrs.

This is a categorically incorrect statement. Some rebuilds may be haphazard, but statement is way to sweeping to be anywhere near truthful.

Sorry. Calling BS on this one.

Peter

One more thing. Saw you have a trawler. Completely different than many sailboat engines as much more likely to have been loaded properly and not be suffering from misuse. And trawlers often have engine rooms where the main can be maintained properly.

[Scott Berg]

if you decide to rebuild the 4-108 (a great engine I'd note) Trans Atlantic Diesel is the go to place for parts and advice... https://www.tadiesels.com/

[mvweebles]

Originally Posted by malbert73

One more thing. Saw you have a trawler. Completely different than many sailboat engines as much more likely to have been loaded properly and not be suffering from misuse. And trawlers often have engine rooms where the main can be maintained properly.

My trawler has a 4.236 Perkins. Same as many 45-60 foot sailboats.

Diesels of all stripes have been successfully rebuilt several times. The 4-108 is most commonly used in generator and refrigeration applications where they often see 10k hours between rebuilds.

I used to be a captain of a 70-ft dinner cruise boat on SF Bay. Engines had 30k hours and on their second rebuild.

I can't explain someone's observation. Could be they had a lousy engine to begin with, could be it was killed via water ingestion, could be a poor excuse of a rebuild which is common (not doing main bearings for example).

[malbert73]

Originally Posted by mvweebles

My trawler has a 4.236 Perkins. Same as many 45-60 foot sailboats.

Diesels of all stripes have been successfully rebuilt several times. The 4-108 is most commonly used in generator and refrigeration applications where they often see 10k hours between rebuilds.

I used to be a captain of a 70-ft dinner cruise boat on SF Bay. Engines had 30k hours and on their second rebuild.

I can't explain someone's observation. Could be they had a lousy engine to begin with, could be it was killed via water ingestion, could be a poor excuse of a rebuild which is common (not doing main bearings for example).

Agree- many different experiences. But MV Weebles how often do you just start your 4-236 to leave the dock to go sailing, or motorsail at low rpms. Right? You’re a trawler so your engine has been used “properly” and can last much longer. Many sailboat owners neglect their engines to a higher degree than you probably and unless you’re the original owner no way to know. Every instance you cite above is a different use profile for a diesel than many sailboats. They are valid as is my point for different use cases

Anyway my point is to present a counterpoint to all those who believe every old diesel is worth rebuilding. Some people are better taking a hard look at what they have and being more objective. A 30-40 year old diesel is 30-40 years old no matter what. Are you replacing every small gasket, oil seal, bearing, valve, hose, etc? So the answer is some diesels have been run properly and are reliable and hence a rebuild is right, and some have been abused and perhaps should be scrapped.

And the experience at Morgan’s Cloud for small sailboat diesel rebuilds (not trawler, truck, or industrial diesels) while a low “n” is food for thought (but NOT an absolute).
I bet none of the 8 of 12 sailboat owners he cites thought they would be re-powering within a year or two of rebuild

And, I bet what you would consider a proper rebuild is labor cost prohibitive in many sailboats because the engine has to be completely removed. So a few K more for a new engine? No brainer

[mvweebles]

Originally Posted by malbert73

...how often do you just start your 4-236 to leave the dock to go sailing, or motorsail at low rpms. Right? You’re a trawler so your engine has been used “properly” and can last much longer. Many sailboat owners neglect their engines to a higher degree than you probably and unless you’re the original owner no way to know.

I used to be a presenter at TrawlerFest, a 4-day series of seminars geared towards aspiring trawler owners. Was held 4-5 times per year in various locations around the country, each attracting about 300-400 people.

I taught two modules, one was docking/close quarter maneuvers, the other was selecting the right boat. I met many sailors considering transitioning from sail to power, many of whom wanted twin engines for redundancy. I used to say that if I took care of my diesel the way most sailors do, I'd want a twin too.

I suppose a lot of the small 2-cylinder engines floating around out there are sort of junky, and there are still a lot of old raw water Universals also out there. They are more trouble to rebuild than they're worth. But the OP asked about a Perkins 4.108, which is immensely rebuildable. Some parts are difficult to source and expensive (I'm told the oil pan is expensive so watch for standing bilge water), but for the most part, a reliable and fairly easy to rebuild engine.

As far as diesels last longer in a powerboat than a sailboat due to usage characteristics, true.....but not the end of the story. Diesels do not die - you have to kill them. Sailboats are famous for killing a diesel via some sort of exhaust elbow break that floods the manifold and subsequent valve and cylinder head damage. Or a water pump bearing leak and ushers water into the crankcase. Or the oil runs low. Or an impellor gets chewed and the engine overheats. This is how a diesel gets killed - and it happens long before the engine is stressed due to under-use or light-load use. It happens through poor maintenance.

There are a lot of wild opinions in this thread. The reality is a Perkins 4.108 with a decent crank is definitely rebuildable. I do question converting from a generator application to propulsion, but it's truly a question - I just don't know how it's governed. Taking the injection pump off the old engine sounds perfectly reasonable, but it's above my mechanical expertise.

Peter

[mvweebles]

Oh, and a couple thoughts for the OP (I just re-read Post #1):

1. I've had great luck with TAD diesel in Maryland. Decent parts availability, and prices seem fair. I've had a Perkins for 25-yrs, including a 4.107

2. You asked about what you should re-build based on it being 'lightly used.' Assuming you're pretty sure it has under about 3000 hours on it, I would fix anything that looks like it may have been leaking. The rear mainseal is a good idea give you'll have it apart. The two water pumps (raw and coolant circ pump) are not too expensive so I'd replace those. The fuel lift-pump isn't very expensive either and tends to seize, so I'd replace that. You may want to consider replacing the on-engine fuel filter with a spin-on adapter if available for a 4.108 which makes changing secondary filters much easier. Would of course change all hoses. You could replace injectors, but you may want to just have the old ones pop-tested at a diesel shop. Might consider replacing the thermostat while you're doing the coolant circ pump.

I guess you could pull the head and have it machined, but frankly, that seems a bit extreme as a prophylactic measure. I'd get it running and go from there. Once it's running, an old trick to see if there is excessive blow-by past the rings is to take the oil filler cap off and put a tissue over the opening to see how much floats-up. Should be minimal, but frankly, tough to say what's normal.

Good luck - I think there's a ton of FUD on this thread.

Peter

[malbert73]

Peter- I think what you said is key- choosing the right engine to rebuild is key. Also, doing the rebuild correctly is key and therein lies the challenge. The 4-108 is one of those engines that could be worth rebuilding.

And, for the PO- compare the power curve of a 4-108 and a Beta 50 and you’ll see a difference. For the same weight and total HP, the Kubota based Beta makes it’s 50 hp at 2800RPM vs the 4-108 which makes it’s 50 at 4000RPM. So for some the repower may be an upgrade....