12v71 - information

We have just purchased an old steel ferry as a project boat. It has a 1970's 12v71 natural in it that has just been rebuilt with less than 100 hours on it. We have several other diesels in the fleet, but none this size, and no 2 strokes or Detroits. Has anyone got any special hints about what to look out for or how to maintain this old beast. Looks like the original engine did around 18000 hours before it's rebuild. We are looking at running around 1000 - 1500 hours per year at light to medium loads, so it would be nice to get a similar life span again if we can get the maintenance right.

Out of interest, the boat also has an old 1940's technology Lister diesel genset. It hadn't been run for years, but after getting it bled (tricky operation) and sorting out a new impeller and a little rubber Y connection that helps lubricate the valves (this is real old school lubrication design this one), it started as soon as I could get the massive flywheel turning. Now it starts first time, every time. I don't know how many hours this thing has done, but I would guess that it is a very large number. Really interesting to get into the guts of these old school engines. Need to find a crank handle for it now and try out the decompression levers etc. Only problem is that this 'baby' 2 cylinder shakes 57ft and 40 tonnes of boat around.

The 12V 71n is very hearty and easy to maintain. Feed it good clean fuel (how are tanks on that old girl?) and keep the air box drains clear and she may exceed her previous mark.
Keepng the cooling system tip top is all important and the oil coolers need to be kept free of scale deposits
Hopefully the vessel has a good array of instrumentation and the skipper can easily monitor water temp, oil temp and oil pressure.
Poor fuel or watered fuel and overtemp are the two worst enemies.
She was made to use a bit of oil so frequent level checks are prudent.
The Lister is a single cylinder I take it? No balance shaft? Just curious.
Good luck.

Thanks JGMO. The Lister is a twin. Going to pull the cooling system off and service it soon so that will be interesting as well I expect.

The oil use on the 12v71 might explain why there is a ~100gal oil tank built into an engine room bulkhead with an external filler like the fuel and water ones. Was trying to work out why such a large amount of onboard oil required. Where are the oil coolers located on these? I take it from your comment they are external and raw water cooled? I haven't spent any time on the main engine yet as it seems to be like new, and there are other more pressing things to sort out (bilge pump system, fire pump system, steering, genset, wiring etc). Will start going through the main engine shortly and setting up the maintenance systems for it, hence my original post. Only an oil pressure gauge and tach on the 12v71 at the moment so a complete new gauge set is on it's way before the boat moves again. No working gauges on the Lister at all so the wheelhouse dash has been ripped out and replaced so there is a nice new home for a full set of matching instruments. Boat had sat on a mooring 'semi-derelict' for several years before we bought it so there is plenty to do.

Man! That sounds like fun! If I were a couple of years younger and a bit more "spry", I'd be sorely tempted to come give you a hand! But, these days, I would just be in the way.

One thing to always keep in mind about DETROIT DIESELS is orientation. This is important for ordering parts and communicating component location. An example would be identifying left cylinder head as opposed to right cylinder head. All orientation is taken as if viewing the engine from the rear. EXCEPT ROTATION. To determine rotation, you stand at the front.

Having said that, oil coolers are typically mounted low and forward on the right hand side of the engine when viewing from the rear. However, you can plumb anything pretty much anywhere if you have enough pipe and ingenuity. This is often necessary on a boat so your results may vary.

I would be shocked if, on a vessel of that vintage, EVERYTHING isn't keel cooled. You would be danged lucky if someone had installed fresh water engine cooling and heat exchanger. Much easier to maintain the engine that way.

No idea why they stocked THAT much oil! Cabin heating perhaps? The Detroit "slobbers" oil from the air box drains and requires monitoring but I'm talking pints and quarts....not GALLONS!

Are you sure the Lister is firing both cylinders? If so, then why all the shakin'? Might need to freshen or re-design the mounts. All that vibration can actually cause fatigue. Both to crew and vessel. It can be surprisingly destructive and can effect instruments, compass and even a helmsman's vision if severe enough.

So many problems!
You lucky guy!
Have a BLAST!
(fun, I mean)

Thanks JGMO. You would have to fly to New Zealand to help so it would be a bit of a trip anyway. Engine and genset are both equipped with heat exchangers so no keel cooling to worry about. The boat is actually a minor celebrity here in NZ as it carried 100's of thousands (probably over a million) people on a well known cruise in the "Bay of Islands" which is one of NZ's best known tourist destinations. The trip is known as "the Cream Trip" and basically cruises the islands picking up milk & cream from the dairy farms on the islands and dropping off supplies etc. We are converting it from a ferry configuration to a luxury day cruise boat for wining and dining etc. So far the hull has been thickness tested (wastage is an issue on steel hulls) and approved for re-entry into commercial work, and I have got most of the mechanical systems working. When we got it, the engine would start and you could steer it. That was all that worked on the boat so we have been going through all the pumping systems, electrical wiring etc. So far 90% of what we have dealt with looked worse than it actually was. A pleasant surprise. Interesting dealing with something that is more 'ship' than 'boat' though. All the valves that we have stripped and cleaned are 4 times bigger than a 'normal' boat and require a whole different set of tools and thinking.

The Lister runs perfectly now that I have sorted out the fuel system and oil flow to one of the valve sets, and doesn't look visibly shaky, but does transmit a lot of vibration. It starts as soon as you get the huge flywheel turning so compressions etc are assumed to be good. Engine is hard mounted to a frame which is on rubber engine mounts to the hull framing, with a flexible steel exhaust section (new) coupling it to the dry stack used for both engines. The engine mounts appear to be OK, but I will change them out for some softer ones and see how that looks. One interesting thing I found was that there was a bleed hose on the hot side of the saltwater flow through the Lister that I traced back through 3 water tight compartments to find that it was the hot water for the sink taps in the toilets. Very strange setup that I assume happened after the boat stopped taking passengers. Heaps to do, but an interesting project.

Oh Yes! New Zealand! We have always wished we could visit. For years, my mother in law had a couple she met during the war come to the USA on "holiday" every few years. We so enjoyed their company! Wonderful people and friends. They have both since passed and our Kiwi connection has waned even though we do get news of their granddaughter from time to time.
No, if I were to come to New Zealand, I would be much too busy "visiting" to work on ships!