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  #11  
Old 02-22-2008
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Ok, thanks Danjarch. Off to bed now, it's pretty late over here.
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Old 02-22-2008
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Engine hours certainly do count. The problem being, are they "hard hours" or "soft hours" ? With proper maintenance and load, or too many hours idling without load? Based on what logs or hour meters? And oil changes, etc?

If you can get a reliable grasp on engine hours and operating conditions, that very much matters. I'm just guessing that the authors felt after 20 years, parts can be problematic, corrosion can be problematic, and so on. But, a good engine, treated well, with parts still available, can last forever.
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Old 02-22-2008
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Quote:
Originally Posted by kengoodings View Post
Our Volvo-Penta MD11C two cylinder Saildrive had no compression or power.
30 year-old Volvo parts are hard to come by and we waited nearly 9 months for components to replace the cylinder liners and rings. After all this time we bit the bullet and purchased a modern 4 cylinder saildrive for $13k A hard decision but full time ocean cruising demands a reliable auxillary in the boat.
We'll have that soon, launch day is fast approaching and our Niagara 35Mk1 will have wings with that 39 hp !!!
Ken and I know each other quite well, and have broadly similar cruising plans, so I feel happy to agree that in his situation, replacement made more sense.

In my case, rebuilding makes more sense. As has been stated elsewhere, total hours and the cooling state make a big difference. So does availability of parts.

My engine is 20 years old, but has only 1,300 hours on it. A rebuild will very likely only reveal ring wear, and some other minor fixes. On the other hand, the pattern of 20 winterizations and low, cold hours could show a problem I don't want to face in Fiji three years from now. Also, my engine is not only fresh-water cooled (anti-corrosion anti-freeze, in fact), but the raw water is fresh water. So the pump, heat exchanger and starter will be replaced, but as they all work very well, they will be the spares for the trip.

My engine takes Mazda spares and gaskets as it's essentially a Mazda pickup block...there's about 100,000 of them still in Australia alone, working and being serviced. A full set of rebuild parts would run me about $7,000, with maybe $2,500 for the labour. A new engine would cost $15,000, plus extensive welding work, tank migration, shaft tube alteration, and so on added to that cost. Lastly, my engine is ridiculously easy to access: drop a hook directly down after lifting off the pilot house roof.

At 2,700 hours on a 29 year old engine, you are facing a situation closer to mine than to Ken's in that I assume it's working well, but it has been used sparingly. If that's the pattern, then the benefits of a new, lighter engine (that runs hotter and needs lots of air to get those fuel savings) might never match another 29 years of the same old engine, but rebuilt.

Just my thoughts...I've been mulling this over for about 18 months now, and my solution is mine alone.
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Old 02-22-2008
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Quote:
Originally Posted by hellosailor View Post
Engine hours certainly do count. The problem being, are they "hard hours" or "soft hours" ? With proper maintenance and load, or too many hours idling without load? Based on what logs or hour meters? And oil changes, etc?

1 engine hr. = 40 miles, that's the industry standard and most people can relate easier to xxx miles vs. xxx hours. (I was a heavy equip. mech. for 30 yrs.)

Hard or soft hrs.?? I never heard of that, but idling any diesel is not good for it and will kill it fast, always put some sort of load on it. The more load it has, the longer they will last. Don't baby a diesel, it's made to run under full load to last almost forever w/ proper care as long as it has the right oil. (Shell Rotella T 15W/40 is about the best all around oil you can buy)


If an engine is rebuilt properly then the starter/injection pump/injectors are also rebuilt at the same time and you basically have a new motor.


"Throw away engines" (just replace, rather than rebuild) don't have replaceable cyl. sleeves.
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Old 02-22-2008
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Quote:
Originally Posted by MacGyverRI View Post

Hard or soft hrs.?? I never heard of that, but idling any diesel is not good for it and will kill it fast, always put some sort of load on it. The more load it has, the longer they will last. Don't baby a diesel, it's made to run under full load to last almost forever w/ proper care as long as it has the right oil.
Maybe we should call Mythbusters in one this one... Diesels really do not care one way or the other as long as they are properly operated and cared for - and in some cases - some diesels like that on my F-350 run religiously regardless of lack of maintenance...

The biggest issue with any engine is over -revving, letting fuel varnish by sitting long periods of time, and in cases of seawater cooled engines - allowing seawater to sit due to not properly ejecting water and properly winterizing...
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Old 02-23-2008
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Jody-

You sound a bit confused in your post. First of all, AFAIK, Diesel fuel doesn't have the varnish problems when sitting for long periods of time, gasoline does.

Second, all engines do care about being run properly. If an internal combustion engine, diesel or gasoline, is run for long periods of time at relatively low loads and for short durations, bad things start to happen. You'll start to get carbon build-up or deposits in the engine. These deposits are normally burnt off when the engine is running under a heavy load. Running the engine for only short periods of time will lead to condensation in the block and rusting from the condensation. This is because the block never really warms up to operating temperatures properly, but is more a problem in gasoline engines than it is in hotter running diesels.

Quote:
Originally Posted by artbyjody View Post
Maybe we should call Mythbusters in one this one... Diesels really do not care one way or the other as long as they are properly operated and cared for - and in some cases - some diesels like that on my F-350 run religiously regardless of lack of maintenance...

The biggest issue with any engine is over -revving, letting fuel varnish by sitting long periods of time, and in cases of seawater cooled engines - allowing seawater to sit due to not properly ejecting water and properly winterizing...
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  #17  
Old 02-23-2008
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Quote:
Originally Posted by sailingdog View Post
Jody-

You sound a bit confused in your post. First of all, AFAIK, Diesel fuel doesn't have the varnish problems when sitting for long periods of time, gasoline does.

Second, all engines do care about being run properly. If an internal combustion engine, diesel or gasoline, is run for long periods of time at relatively low loads and for short durations, bad things start to happen. You'll start to get carbon build-up or deposits in the engine. These deposits are normally burnt off when the engine is running under a heavy load. Running the engine for only short periods of time will lead to condensation in the block and rusting from the condensation. This is because the block never really warms up to operating temperatures properly, but is more a problem in gasoline engines than it is in hotter running diesels.
No I am not confused about my post. Owning a wide variety of powered contraptions... That rarely get used but always get up and go... However, I pay attention to the fuel... And FYI Diesel degrades.. while may not varnish will give varying declining return depending on volume and sit time... Which is the problem most sailboats have as a engine is an auxiliary source of power...
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  #18  
Old 02-23-2008
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Jody-

I never said that Diesel fuel doesn't degrade... just that it isn't generally going to turn into varnish, like gasoline does. The declining quality of fuel, whether diesel or gasoline, has much more to do with the more volatile components evaporating off than anything else.

Gasoline has additional problems since the introduction of ethyl alcohol as the primary octane booster/oxygenator, since the ethanol will start to separate out once the water content reaches 1.5% by volume or so... making the remaining gasoline about 84 octane or so.

BTW, ethanol has replaced MTBE, which was the previous octane booster used in unleaded gasoline, but had some serious issues, since it was both a carcinogen and water-soluble IIRC. MTBE replaced tetra-ethyl lead, which was the most common octane scavenger up until the advent of the catalytic converter. The platinum catalyst in the catalytic converter is contaminated by lead, and the Clean Air Act of 1970's requirement of catalytic converters was a primary reason for leaded gasoline being phased out.

Diesel fuel is helped quite a bit by modern fuel stabilizers, and shouldn't be that much of an issue. The biggest problems with diesel fuel over long periods of time are condensation and the resulting growth of bacteria at the water-diesel interface. Modern fuel treatments help with both of these problems to some degree to, within reason.

Quote:
Originally Posted by artbyjody View Post
No I am not confused about my post. Owning a wide variety of powered contraptions... That rarely get used but always get up and go... However, I pay attention to the fuel... And FYI Diesel degrades.. while may not varnish will give varying declining return depending on volume and sit time... Which is the problem most sailboats have as a engine is an auxiliary source of power...
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  #19  
Old 02-23-2008
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Originally Posted by sailingdog View Post
Jody-

I never said that Diesel fuel doesn't degrade... just that it isn't generally going to turn into varnish, like gasoline does. The declining quality of fuel, whether diesel or gasoline, has much more to do with the more volatile components evaporating off than anything else.

Gasoline has additional problems since the introduction of ethyl alcohol as the primary octane booster/oxygenator, since the ethanol will start to separate out once the water content reaches 1.5% by volume or so... making the remaining gasoline about 84 octane or so.

BTW, ethanol has replaced MTBE, which was the previous octane booster used in unleaded gasoline, but had some serious issues, since it was both a carcinogen and water-soluble IIRC. MTBE replaced tetra-ethyl lead, which was the most common octane scavenger up until the advent of the catalytic converter. The platinum catalyst in the catalytic converter is contaminated by lead, and the Clean Air Act of 1970's requirement of catalytic converters was a primary reason for leaded gasoline being phased out.

Diesel fuel is helped quite a bit by modern fuel stabilizers, and shouldn't be that much of an issue. The biggest problems with diesel fuel over long periods of time are condensation and the resulting growth of bacteria at the water-diesel interface. Modern fuel treatments help with both of these problems to some degree to, within reason.
We actually do not disagree less that I felt you were trying to hit the finer points that I may have left out. Ironically with lead almost minimal in fuels a catalytic converter is still required... ironic? My original points I stand behind - having 5 vehicles, (one diesel)... plus the boats - I am more aware of the damage of bad fuel than most... also - more aware that one doesn't have to be overly energetic either... which was my point.. 20 years - semi regular maintenance and concentration on fuel quality goes a lot longer way than regularly doing every maintenance aspect and neglecting the fuel (which I think most do - considering when wintering - it sits for for six month or so and regardless if it is varnish or bio containments (diesel) - fuel is probably one of the top contributors to engine problems due to the nature of how sailboaters use the engines...
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  #20  
Old 02-23-2008
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I tend to disagree on the "myth" that says a diesel engine will get glazed cylinders because it has idled too long. If it is running at proper temperature and is burning cleanly (proper fuel metering, clean injectors, clean fuel) there really should be no reason for it to leave enough un-burned fuel in the cylinders for it to build up. There are hundreds of thousands diesel trucks on the road that run at idle for hours while at truck stops; as well as tractors that sit idle between jobs, and they don't "glaze" while running at idle.

I think that under-loading the engine while motoring is a bigger problem. Most sailboats have undersized props to reduce drag and the hull form is easily driven for efficiency; so the engine never sees the loads that it should regularly get to keep it from getting carbon build-up, dirty injectors and valves. In addition the wet exhaust wears on the engine due to the salt vapour (while sitting dockside) and back pressure while running.

I suggest doing a few acceleration runs now up to max RPM now and then while motoring (when engine is fully warm). If you get black smoke puffing out at first; do it a few more times and it should clear. It is just carbon getting flushed out of the combustion chamber and exhaust.

Let your engine warm up when starting from cold; it is important to warm up the engine oil before putting it under load. I'd be more worried about bearing and cylinder wear while running the engine under load when cold than causing cylinders to glaze. I'd be willing to bet that most if not all diesel owners manuals recommend warming the engine before driving/revving.

On the issue of rebuild vs. replace; well that depends on what your plans are and if you can DIY. A rebuild is almost always cheaper if you do your own work. If your engine is only stubborn to start or has some other problem (smoking, rough idle, etc) it might be worth having a mechanic look at the engine and diagnose the problem before you drop big bucks on a new powerplant. Too often the problem is a simple repair and the engine is otherwise fine (but the owner thinks it is tired/worn out). Sometimes all that is needed is a cylinder head rebuild; or a new starter, injector cleaning, injector pump, etc. These are maintenance items for a diesel engine; and should not be overlooked. Change your oil every 100 hours or 6 months; keep it topped up. Do the regular maintenance like pencil zincs, coolant, impeller, fuel filters, injector maintenance if needed, and your engine should last almost indefinitely.

Last edited by KeelHaulin; 02-23-2008 at 06:25 AM.
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