Bullet Proof Diesel

[valhalla360]

The reports on Yanmar are more likely the result of volume.If 1 in 10,000 motors will sieze in the next year (regardless of brand) and there are 50,000 Yanmars of various ages floating around and 100 of brand X motors, odds are you will see 5 Yanmars siezed per year and you may never see a brand X fail even if they have the same failure rate.

That said, we love our 4stroke EFI outboard. Simple, quiet, fuel efficent and worst case scenario $5k and we have an entirely new drivetrain. Pluse we have directional thrust, so we can back as easily as going forward. Nothing at all like the old 2 strokes. Of course, our boat was designed for outboard power. If you are cobbling an outboard onto a boat designed for diesel inboard, that's a different situation.

[captain58sailin]

I would never buy a diesel named "brand X" that is just asking for trouble

[Blue Crab]

Wish I had a good feeling about running my Yanmar 2GMFW20 around 2200. Lotsa folks say thats too slow but it's easier on me. It's economical and close to hull speed.

Some say idling kills them, others get 10K hours.

We can put a man on the moon but don't have definitive answers for simpler stuff.

[a64pilot]

Buy the boat you want, regardless of the engine brand, don't accept a baot you really don't like because it has the right engine.

My personal caveat to that is I won't have a Volvo, if I found a boat I really had to have that had a Volvo in it, I'd figure re-powering cost into the price.

I don't care who makes the engine, you don't want it raw water cooled. Outboards get away with raw water cooling, but I believe that is because they are a clean sheet design to use raw water cooling, most if not all boat Diesels are adapted from terrestrial designs and "marinized"

[captain58sailin]

I have had extensive conversations with marine engineers about the best speed to run a Detroit diesel for longevity and fuel consumption. The answer I got was 1700 rpm would get me the best of both. This was for a 471 or 671.

[colemj]

Originally Posted by captain58sailin

I have had extensive conversations with marine engineers about the best speed to run a Detroit diesel for longevity and fuel consumption. The answer I got was 1700 rpm would get me the best of both. This was for a 471 or 671.

These are 2-stroke, 2000rpm engines. 1700 would be very low for a smaller, higher rev engine.

Most engine manufacturers publish rpm curves for HP and fuel consumption. There is no "best" general rpm - that is dependent on the specific engine and the load it is under.

Mark

[mbianka]

Diesels and sailboats don't mix. I found that out when my good running Westerbeke 27 went from perfectly running engine to a non starter in six hours. Despite oil changes every 50 hours and/or seasonally, zinc and antifreeze changes etc. Diesels work best and last longest when driven hard and often. Not for minutes at a time to get out of the harbor. Expect the diesel to fail at some point no matter what manufacturer. Then your choice is repair/rebuild, replace or as I did change to electric propulsion. It may not suit everybody but, in seven years with EP my maintenance cost have dropped pretty close to zero in comparison to the previous diesel engine.

[Wotname]

Originally Posted by a64pilot

Buy the boat you want, regardless of the engine brand, don't accept a baot you really don't like because it has the right engine.

My personal caveat to that is I won't have a Volvo, if I found a boat I really had to have that had a Volvo in it, I'd figure re-powering cost into the price.

I don't care who makes the engine, you don't want it raw water cooled. Outboards get away with raw water cooling, but I believe that is because they are a clean sheet design to use raw water cooling, most if not all boat Diesels are adapted from terrestrial designs and "marinized"

Hmm... I have only had 4 engines but they were all raw water cooled. I haven't ever experienced a problem with raw water cooling but I suppose there will come a time. I do hear about heat exchangers giving problems but having never owned one, I can't really comment further.

AFAIK, Bukh & Yanmar both used a "clean sheet" design for their raw water cooled engines.

I concur that terrestrial designs would be better off with a heat exchanger.

[Panope]

Originally Posted by Blue Crab

Wish I had a good feeling about running my Yanmar 2GMFW20 around 2200. Lotsa folks say thats too slow but it's easier on me. It's economical and close to hull speed.

Some say idling kills them, others get 10K hours.

We can put a man on the moon but don't have definitive answers for simpler stuff.

BC: I would operate the engine as per the Yanmar operations manual. Not sure what yours recommends, but mine tells me "when oparing the engine at reduced power settings, race the engine every 2 hours". The process for racing the engine is described as moving the control handle from idle to max speed and back to idle 5 times while transmission is in neutral.

The above implies that yanmar does not think it is bad to run the engine slow.

Steve

[darylat8750]

Be sure to note the difference between "Raw water cooling" in which sea water flows through the engine block, which is bad, and "Sea water cooled" or some other phrase in which the sea water flows through heat exchangers for the engine and transmission which is good. Keel cooling also has many advocates.

I've run several boats with Yanmars. I think they are good engines. My irritation with them and Volvo is that the companies won't give you cross reference numbers so you can go to a tractor dealer or NAPA and get parts. My friend had a 2 month night mare stuck in Columbia while Volvo shipped the required parts to Minnesota the to the US Virgin Islands before finally sending them where she asked them to send the stuff in the first place. My old Ford Lehman engines are supported anywhere in the world. If I were looking at newer engines I would lean towards Beta at 100HP and below and John Deere above that. That said if I saw a boat that I wanted at the right price I might own another Yanmar or Volvo. Everything is a trade off.....

[Wotname]

Originally Posted by darylat8750

Be sure to note the difference between "Raw water cooling" in which sea water flows through the engine block, which is bad, and "Sea water cooled" or some other phrase in which the sea water flows through heat exchangers for the engine and transmission which is good. Keel cooling also has many advocates.

.....

Hmm... am I the only one who thinks "raw water cooling" is quite OK - assuming engine is designed for it. As posted above, I have yet to have a problem with raw water cooling - over 4 engines to date.

Maybe I have just been lucky

[Blue Crab]

Originally Posted by Panope

BC: I would operate the engine as per the Yanmar operations manual. Not sure what yours recommends, but mine tells me "when operating the engine at reduced power settings, race the engine every 2 hours". The process for racing the engine is described as moving the control handle from idle to max speed and back to idle 5 times while transmission is in neutral.

The above implies that yanmar does not think it is bad to run the engine slow.

Steve

Yeah, I read that and blew on by it. That is good to know.

[Saltyhog]

Originally Posted by Wotname

Hmm... am I the only one who thinks "raw water cooling" is quite OK - assuming engine is designed for it. As posted above, I have yet to have a problem with raw water cooling - over 4 engines to date.

Maybe I have just been lucky

If the engine was designed from the ground up to be raw water (read SALT water) cooled, it should provide reasonable service. Raw water cooled engines will usually be designed to run at cooler temperatures than fresh water (coolant) cooled engines. This is to prevent precipitation of salts in the engine's cooling passages. The thermostat's opening temperature will be selected for that lower temperature. Machining tolerances will also be selected for the lower run temperature. The downside is that a diesel engine will run less efficiently at the cooler temperature. Diesel engines run best when hot. (but obviously not so hot that they damage themselves)

[ranger58sb]

Originally Posted by Fullblown

Thanks for all your advice, I can see now that a Yanmar would be okay if it has been looked after and that begs the question, how would I know if its been looked after. Do I ask for service records, probably hard if the boat is over twenty years old and had a few owners. Do I insist on engine report before buying.

Yes, it's common to ask for -- and then actually look at , when supplied -- service records. Yes its common to have a separate engine report (aka mechanical survey), even in addition to a service record review. Usually the latter is best performed by a specialist in whatever brand engine you're examining.

Cooling with a heat exchanger is often called "fresh water cooling" around here. Fresh water (more likely a mixture of -- ideally -- distilled water and anti-freeze) is routed via several small freshwater tubes through a larger heat exchanger jacket which has sea water continuously pumped through it and then out through a wet exhaust.

-Chris


-Chris

[captain58sailin]

Doesn't hurt to send in an oil sample for analysis. Even if you don't have a historical record, it will give you an idea in general about the status of the engine condition.