# Care and Feeding of the Perkins 4-108



## PearsonCommander (Feb 10, 2009)

We just bought a new boat with a Perkins 4-108 with a Hurth transmission. We would like recommendations for engine and transmission oils and fuel additives. Any other wisdom would be appreciated. The engine seems to be running well and we would like to keep it that way – fingers crossed.


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## WanderingStar (Nov 12, 2008)

You can find origainal engine manuals online. I found them at a Cape Dory Owners site. They are also available on ebay. My 4-107 transmission uses the same oil as the engine, so did my yanmar.


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## PearsonCommander (Feb 10, 2009)

Yes, we have copy of the manual. But has anyone tried the newer synthetic oils? And waht about fuel additives? Do you use them?


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## btrayfors (Aug 25, 2006)

The Perkins 4-108 is one of the most ubiquitous and most reliable engines found on sailboats. It will outlast you if treated right. They all leak a bit of oil; not much you can do about it except use absorbent pads. I fitted a Walker Air-Sep about 5 years ago; it helps reduce the oil leaks by maintaining a negative crankcase pressure.

Maybe synthetic oils are OK, but I wouldn't use them in mine. No data to disprove their beneficial effect, but regular diesel oil works just fine. And, I believe, it should be changed at regular intervals. Good, clean oil is cheap insurance.

A few years back I fitted an automatic oil change device. It makes oil changing a breeze; takes less than 10 minutes, no fuss, no mess. Encourages you to change the oil when you should, and not wait.

The Hurth transmission is something else. Some have had good luck with it; others have sworn it's a piece of garbage. Guess you'll just have to baby it and keep fingers crossed.

Bill


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## CalebD (Jan 11, 2008)

A good oil is Shell's Rotella T. It comes in SAE 30 or 15W-40. What weight oil does the manual say to use?
It is one of the few oils that is good for both compression and spark engines (dieseal & gas).
As for fuel additives (snake oils) there seems to be little proof of most of their claims. Using a biocide in diesel tanks may help if you have a bacteria problem in your fuel, which starts with water in the fuel.
Clean oil, clean fuel and clean filters are your friends.


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## killarney_sailor (May 4, 2006)

*Check this website for more information*

Ask Dr. Diesel - Answers to All Your Industrial Engine or Transmission Technical Questions

There is quite a bit of good information here about engine oils and transmission fluids. There advice can be a little worrying as they say that Hurth transmissions are delicate and often boat builders put a smaller than needed transmission on a particular engine to save a few bucks.

These guys suggest half synthetic and half regular engine oil (in both cases oil designed for diesels) and synthetic transmission fluid. I just replaced my transmission oil with Mobil 1 synthetic.


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## PearsonCommander (Feb 10, 2009)

Can you tell me a bit more about the automatic oil change device?


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## PearsonCommander (Feb 10, 2009)

Still hoping for some additional details on the 4-108...In particular:

1)	Additives to deal with change in sulfur content of last 20 years?
2)	Walker AirSep?
3)	Easy oil change systems, X-Change-R System?
4)	Synthetic Oils?
5)	Biocides?
6)	Lubrication for the Hurth transmission?
7)	Good independent mechanic in the San Francisco area?

Thanks in advance for any help?


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## KeelHaulin (Mar 7, 2006)

For "additives"; I have been using Diesel Kleen with Cetane boost. But I have also been running ~60% bio-diesel and the bio-diesel has a low Cetane. Without the booster I was having some difficulty getting the engine to start on cold days.

I have been running Delo-400 15W-40 for engine oil. It's possible that a synthetic would be better in the long run; but with such low hours (6 months or 100 hours) between changes I would say that the benefit would probably be minimal.

You deifnitely want to run a biocide; but if you can't get into the tank and clean it of growth then you should be careful. Biocides (and bio-diesel) will tend to break the growth free in the tank and can clog filters. So it's best to have a dual filter system that you can switch to the back-up filter and change the clogged filter if needed.

What repair work do you need done on it?


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## KeelHaulin (Mar 7, 2006)

On the low-sulfur diesel issue; the new ULSD (ultra-low sulfur diesel) is low in lubricity; and tends to cause seals that are not designed for it to harden. On the opposite end of the spectrum; bio-diesel tends to soften rubber/seals and fuel lines that are not the new type. So I decided to split the difference and run 50% to 2/3 bio-diesel and ~1/3 ULSD. It has been working fine for ~2.5 years now and the only fuel line I had to change was the return line from the engine to the tank. Everything else was already newer lines.

For oil changes I use a tool called "Suck-Up"; it is a hand operated vacuum pump (looks like a garden sprayer but makes a vacuum instead). I bought it at Whale Point Marine in Richmond, CA. The 4-108 has a port low on the left side with a cover plate that you remove to insert the vacuum hose. I think it also could have an optional OEM vacuum pump installed there; but my boat did not have one due to space constraints.


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## TSOJOURNER (Dec 16, 1999)

After numerous discussions, we have decided that the arguments in favor of additives make sense for both lubricity and biocides. Would others who use these additives on the 4-108 like to share their brands and amounts?

Thanks


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## SteveInMD (May 11, 2007)

I run a biocide and PRI-D which is a stabilizer (both from WM). I follow the amount listed on the bottle.


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## meuritt (Aug 25, 2008)

My recent purchase has a Perkins 4-236. Chucks Marine in East Bay has cared for this engine, according to his records, for 15 years. I have contacted him twice with questions and have gotten prompt, with two days, polite and friendly answers. I've moved my boat to Marin, he is willing to come here, if he has more than one appointment to justify the trip. 

This is my contact for him 510.272.0765

Mike
San Rafael


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