Perkins 4-108

[Steve Kidson]

Three years ago I bought a second hand 4-108 for my boat as part of her re-fit. It had been removed from a boat being re-powered with a Yanmar, and the mechanic was selling it on behalf of the owner.

On inspection at his shop, engine started first time with minimal turning over, and that was from cold.

After installing I would turn it over by hand every few weeks to keep oil circulating and prevent seizing.

Just after Christmas, and now much closer to being in the water, I had bought a 12v battery booster and thought it would be much easier to connect this for the routine turning over.

Imagine my surprise when after about 15 seconds of turning over it came to life; obviously there was still fuel in the filter, and although all new fuel lines have been connected, there is no fuel in tanks. It blew no great clouds of smoke - exhaust has yet to be fitted, and for the short time I let it run sounded sweet.

I calmly reached for the fuel shut off solenoid and manually shut down fuel supply, but was so impressed with the obvious reliability of this motor. I have read much about them in discussions here and am pleased with my descision and choice of motor. They must be almost bullet proof!

I am now madly working on connecting remainder of cooling system and exhaust so I can run it again - just for fun .

I know that when it gets into the water it will run without a problem.

Fair winds

Steve

[Alan Wheeler]

Great to hear Steve. When I started reading this, I though uhoh is this going to be a horror story.
Ummm, I do hope you didn't run it with a dry pump impellor. Worth fitting a new one when you commision her anyway.

[ssullivan]

Steve, I too, am a convert! These engines are true work horses. They are much heavier than a Yanmar of equal HP. To my untrained eye, they seem like they would last many hours beyond what a Yanmar would... plus... parts are so easy to find. These engines are supposedly in taxis in England, and definitely in many forklifts and gensets throughout the world. They have a huge following. It never ceases to amaze me how great this engine is either. I had to motor my boat through the Erie canal, and for a good part of a 2000 mile trip from Wisconsin when I bought her. I thought for sure that the old Perkins would die along the way and that I'd have to do some major mechanical work. I also had been told (from a broker probably?) thatYanmar engines were superior. Truth be told, I think a Perkins relates to lightweight new engines, just like any really solid product from the 70's and 80's relates to the modern plastic version. (not trying to start any kind of engine war... just saying they are *solid* metal). It's also a simple engine. You look at it and understand it without much in the way of electronics. Very nice, right?

[never monday]

Originally Posted by ssullivan

not trying to start any kind of engine war... just saying they are *solid* metal

Hum....
I do like the Perkins BUT they have their issues too, like all other man made things.

[Pblais]

They must be almost bullet proof!

I just love it when the magic works.

I would stow the bullets for now. You need as much going for you as you can. I have two boats for the time being one with a perkins and the other a Westerbeke. They are both of a similar nature but they both just run. The each have their own rituals on how they start - but they do.

The newer engines are trying to give you that trun the key and it starts like your Honda in the garage feel. It is is something like that that seesm to be pushing the newer designs. Maybe they will eventually get there too.

You might want to think about rebuilding your Perkins in say 6,000 hours. No telling where you might go until then.

[ssullivan]

Originally Posted by never monday

Hum....
I do like the Perkins BUT they have their issues too, like all other man made things.

I'll defer to the experts here...

Obviously, Never Monday knows these things better than a single, isolated experience. So what are some of the known issues that we all should watch out for on these old engines?

[ssullivan]

Originally Posted by Pblais

The newer engines are trying to give you that trun the key and it starts like your Honda in the garage feel.

Oddly, mine does just that if it hasn't been sitting without being started for 3 months or more. I found it's just a matter of getting some fuel primed up to the injectors in my case when it has been sitting for a few months. If your engine's been sitting and you're short on battery power and worried about a long cranking time, just hit that manual primer with 3 quick pushes and it starts like the Honda in the garage every time.

[never monday]

Sean,
The biggest problems I've seen with the 4-108 is oil leaks from every gasket on the engine and the 2 piece rear crank seal. Everything in the raw water system is subject to corrosion. The heat exchangers are pricy when they finaly let go. Granted it's usualy in the 20th year and $1500-$2000 amortized accross that life span isn't much, but it's a chunk of change. The stamped sheet metal timing gear cover and oil pan are vulnerable when the raw pump leaks. If you stay on top of maintainance then you should get 10K + hours. The 4-108 is a classic that will go down in history as a true workhorse. I think it should be imortalized with the Cat 3208, VW air cooled engines and the Volvo MD series.
Yanmar has concentrated on lightening, and minimizing the size of the small engines. This allows for better utilization in more boats, pumps and generators. After all the market is demanding "more power" in a smaller package. Look at Hondas S2000 engine, 240hp from 2L. The old 4-108 was 50hp from 2L
Back on topic, in a heavy weight cruiser, an older IDI diesel with low rotation speed and high torque is the way to go. Contrast that with new boats. The new market needs a small light engine to power the boat, charge batteries and most importantly. Fit with minimal impact to the living space of the boat.
Thoes that can keep up with the old iron them selves will in the long run be better off. If you personaly lack the knowledge or desire to get dirty. Go for the new iron, it's just as good. Only different.

[ssullivan]

Excellent post, Pat. They sure do like to leak. I have a few gaskets leaking, just as you describe. I use baby diapers to make sure none of that oil ends up in the bilge. When I change the oil, I change the 4-108 baby's diapers as well.

[btrayfors]

I've lived with my 4-108 for 17 years now, and my son just bought an older sloop with a 4-108, so I know them pretty well...from a user's perspective.

As Pat says, they leak. Had my front cover plate replaced last year and it leaks much less. However, a few absorbent pads under the engine keeps the oil from reaching the bilge.

Mine still starts within a few revolutions, after all these years. It's quite amazing. And, I don't have a glow plug of any kind.

Had an overheating problem for years in the Caribbean; finally solved that with a few tweaks and a larger heat exchanger.

If you ever have to replace the circulating pump, be careful: there's a steel plate which sits between the pump and the engine block and has a gasket on each side of it. These gaskets are NOT identical.

While rated variously at 42HP, 47HP, 50HP, etc., this engine is overrated. It's a small engine, despite it's bulk and weight, and should be rated down around 30-35HP in actual use.

Parts are easy to find from lots of sources. I've found Foley Engines in MA to be a good source, though some have found them difficult.

A few years ago I purchased and installed a Walker AirSep for my 4-108. The difference in cleanliness of the engine room is hard to believe. It's a truly wonderful thing to have, and well worth the $400 or so.

Another upgrade which I'd say is just about mandatory is an easy oil change system (I bought an XChanger system). For years I just sucked oil out the dipstick, but found that it doesn't evacuate ALL the oil and, worse, the sludge which forms in the bottom of the oilpan. Over the years, the amount of sludge buildup was unbelievable. Much better to drain the oil from the oilpan.

Love that old engine which has taken me literally tens of thousands of miles.

Bill

[AnchorageGuy]

I can't add much to the previous posts but our 10 year old 4-108 was finally replaced with a Yanmar 56 for one basic reason. Without going into details the end result after many conversations with the Perkins people the engine was only delivering 26HP at the prop even though it was rated at 50HP. Not sufficient for a 14 ton cruiser. That rating is on a bench and not installed in a boat. The rated HP can not be achieved in a marine installation. Our Yanmar delivers 56HP at the prop. A big difference. The old Perkins was running strong when we removed it and was sold to another boat owner. I believe it is still going strong in its new home. We spent lots of money trying to stop the oil leaks to no avail and finally gave up and kept a good supply of absorbent pads on the boat at all times. The engine had 2400 hours when we did the re power.

[Alan Wheeler]

It doesn't matter what model Perkins you have, they are all natoriouse at leaking oil. One of the main area's and easiest fixed, is the tappet cover. If you ever have this engine out, I strongly suggest you do not replace gaskets with the perkins gaskets, but instead use the Red silicon gasket maker in a tube. This will solve the leaks.
The HP tratings is a difficult one. The big problem is comparing apples to apples. Perkins makes one mistake. They are too honest ;-). No actually they publish too many figures. Great for the designer/engineer, but confusing to the ordinary Joe Blogg. They publish all the different "types" of HP ratings. SAE, DIN, SHP, and so on and so on. That's great if you know what rating you should use for what job. The apples to apples part is comparing say a Yanmar HP rating the same as the Perkins rating. It is quite possible two different ratings are being used. Which rating is used is often due to whom is selling the engine or boat with the engine in it.
There is one advantage of Diesel over petrol engines. Diesels derive there power in set specific ways. The ltr/cu" of the pot plus the fuel doesed determins in a ruff rule of thumb, the HP. The length of stroke/burn time, determins the Torgue. X amount of CC plus X amount of fule delivered produces X amount of power. I have to dig around and look it up, but I do have the figures in my text books somewhere. The length of stroke and the burn time determin the Torgue. The Torgue and the power are related to the measured dose of fuel. It could be said that the the Sum of Torgue and HP equals the work done. Just like Volts x amps equals Watts. So when looking at specs of engines, you have to look at more than JUST the HP. A 2 ltr NA Yanmar will deliver ruffly the same TOTAL power as a 2Ltr NA Perkins. But how that total power is delivered, either torque or HP maybe different.
The other big difference with Yanmar is they are more commonly Turboed. A Turbo gives an instant 50% more power for the same CC rating. Perkins being great work horses lend themselves well to turboing. But like anything, the more power you get out of an engine, the less life the engine will have. You can't get something for nothing.
I hope all that isn't too confusing.

[ssullivan]

Actually, Wheels... that makes perfect sense.

[SkiprJohn]

I would like to add that my old 4-107 was a great engine too and never let me down. No 4-107/4-18 never produced 50hp
JohnL

[Pblais]

A Turbo gives an instant 50% more power for the same CC rating.

But at a cost of more fuel consumed fuel due to air forced in to aid the combustion. The power has to come from some place. With power boats like trawlers running twin engines it's like going 8 knots compared to 13. But oh the fuel bill. All my trawler friends now run just under the turbo so they can enjoy the longer ride and save money.

With cars it's actually nice. You use that burst of turbo and suddenly accelerate and then kick back and cruise down the highway as the turbo cuts out. My VW 1.8 liter with the turbo picks up just nice. I had the turbo go out and without the turbo the car is terrible. Not so with a boat. Turbo goes on and stays on. It's no wonder the turbo takes it's toll on the engine. The stress has to be tremendous.