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Old 24-06-2021, 11:53   #1
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Engines, hours, and brands

What’s the best and worst when it comes to a baby diesels? How many hours do they REALLY run (not just “we rebuilt them at 3500 hours because we wanted to”) I understand there are many factors like maintenance and average loading, but I don’t have a ton of experience in the smaller diesels. In cars they can range in longevity by huge margins.
I’d also possibly be a little more willing to run critical parts until failure simply because in a twin engine craft you can still have some engine if you let one go all the way until failure. Of course that does seem like tempting Murphy a bit lol. Just noodling on diesels at the moment because I’m tying to figure out why twin outboards are not more common on cats of all sizes actually but especially the smaller cats.
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Old 24-06-2021, 13:44   #2
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Re: Engines, hours, and brands

The boat I have came with 2 x 3gm30 Yanmar diesels. At some point they changed the hour meters and if the old hour meters + new hour meters were to be believed, they ran for about 5k hours before being replaced.

The motors still ran well and didn't burn oil or lose fluids. They still produced power and they would start without much complaint. However....

The pulleys in the front of the engines were pitted and burning belts like crazy. The water pumps needed to be replaced and were very expensive. The fuel lift pumps both rusted through and were getting dripped on by leaks in the cooling water system that needed replacement. One engine sprung a leak in the high pressure fuel line where it had rusted through. The engine panels were in bad shape, buzzers dead. New yanmar panel buzzer was 500 dollars! The SD20 saildrives (20 years old) were about shot as well.

In short, the engines still had life in them but everything "around" the engine was dying. I could have pulled them and fixed all these problems, but then I'd have spent over a third of the cost of new ones for well running 20 year old motors.

I think if you treat them right, they'll last a very long time. Keep your hatches tight and don't let the damn things get dripped on.

Side note, I replaced a Perkins MD50 in my last boat at 6000 hours. Personally I plan to get 8000 hours of a small marine diesel that is cared for and 4000 hours out of one if I don't know how well it was cared for.
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Old 24-06-2021, 14:14   #3
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Re: Engines, hours, and brands

Three data points for you:

1976 Westerbeke 4-154 (Block made by BMC). Sold the boat in 2015 with 9000 hours. Ran like a top.

1996 Volvo TMD22 (Block by Perkins) currently 9000 hours. Runs like a top. No problems, no issues.

1996 Onan generator (Kubota powered) retired at 8500 hours. Motor ran without issue, but Onan no longer supported the electrical side with spare parts.

These are all the small diesels I have owned. I have worked on many, many others. Any small diesel that does not last at least 10000 hours has been abused. Note well that some of the worst “abuse” includes not being used.
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Old 24-06-2021, 14:19   #4
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Re: Engines, hours, and brands

I think 4–5k with neglected maintenance, abuse
8500-10k with service and preventative maintenance, working them properly. I wouldn’t be surprised 12+k.
+1 ThereAndBack about external corrosion on engine and components l.
Know best practices, ie; crank/no start to circulate oil if engines not been run for awhile. What’s awhile? For me a week w/out running, I stop/crank for 8-10!sec before starting.
Annual oil change regardless of hours, for “occasional “ use category.
Watch excessive idle, warm up. And few revs before shut down. I find PRI D along with Bio treatment has my 3jh very happy.

To combat external corrosion, Ive adopted 1-2x year depending on use. On a sunny, warm day I use brake cleaner, degrease as necessary. W/a garden pump sprayer with salt away, mixture sparingly spray the engines and accessories down.
Leave deck hatch’s open to dry. When dry i coat entirely with corrosion block.
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Old 24-06-2021, 15:19   #5
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Re: Engines, hours, and brands

From personal experience the 3 engines that stand out as problematic are Lombardini ( the unit injector ohc model).... Volvo Penta (earlier, pre shibaura small engines and current common rail engines) and finally Steyr.
By far the biggest cause of early failure right across the small ( up to 200hp) engine range is raw water cooled exhausts, they do a lot of harm for a long list of reasons from catastrophic lockup to slow insidious cylinder/ turbo valve corrosion. There could be a whole new thread just on damage caused by wet exhausts.
I like Yanmar, all of em , Perkins most of em , Ford are an oldy but a goody and Detroit Diesel which are now quite rare outside the US. There are more but I’d like to hear what others love and hate first.
Pete
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Old 24-06-2021, 17:03   #6
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Re: Engines, hours, and brands

Don’t defer maintenance/ inspection of wet exhaust systems. Definitely has various consumables that need replacing to maximize engine longevity. Not sure why my Yanny 3jh has no zincs. Also holding. my 3jh5e exhaust manifold will last 8-10k miless. 1700hrs I believe previous owner may have only serviced. 1x. I could be wrong. There’s definitely some corrosion (normal) showing at flange area. I used some metal putty to fill some of it in, on recommendation from the radiator shop.
Had no idea about ultrasonic cleaning…
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Old 25-06-2021, 19:02   #7
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Re: Engines, hours, and brands

I have a Yanmar 4jh5e with 4500 hrs, the marina that I belong to run there 4 launches on the same motors. They do oil changes every 100 hrs and a rebuild at 10k hrs not because they have to because that’s part of there maintenance program. They have an extra 4jh5e so one motor is on the blocks getting rebuilt or is ready to install at all times.
I took a Yanmar small engines class and the instructor told us the new motors are hard to work on by DIYers because of all the extra hardware on the motors to accommodate EPA regulations. He said an engines longevity is directly related to the maintenance and attention it gets, keep it cool, keep it clean, do the scedualed stuff and buy spare parts of the important things belts, impellers, heat exchange fittings, fuel injectors, fuel filters, engine room fans, oil, and oil filters, keep them dry, and they should last for evah!!
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Old 25-06-2021, 20:41   #8
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Re: Engines, hours, and brands

Do these little engines typically run timing gears, chains, or belts?
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Old 25-06-2021, 21:16   #9
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Re: Engines, hours, and brands

Timing gears are the most common but the Perkins Prima has an overhead cam and timing belt, rare to see a timing chain.
Pete
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Old 25-06-2021, 21:46   #10
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Re: Engines, hours, and brands

My Westerbeke 30B has about 450hrs on her, barely broken in. Great little engine, easy to work on, runs very well.
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Old 25-06-2021, 22:04   #11
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Re: Engines, hours, and brands

Quote:
Originally Posted by Kd9truck View Post
I have a Yanmar 4jh5e with 4500 hrs, the marina that I belong to run there 4 launches on the same motors. They do oil changes every 100 hrs and a rebuild at 10k hrs not because they have to because that’s part of there maintenance program. They have an extra 4jh5e so one motor is on the blocks getting rebuilt or is ready to install at all times.
I took a Yanmar small engines class and the instructor told us the new motors are hard to work on by DIYers because of all the extra hardware on the motors to accommodate EPA regulations. He said an engines longevity is directly related to the maintenance and attention it gets, keep it cool, keep it clean, do the scedualed stuff and buy spare parts of the important things belts, impellers, heat exchange fittings, fuel injectors, fuel filters, engine room fans, oil, and oil filters, keep them dry, and they should last for evah!!


I totally agree with good routine maintenance and it’s great to visit a boat that has the change date and hours written in magic marker on all the filters or a log book with all the service history and no argument about those engines lasting longer BUT, the reality is that almost all the dead engines I’ve replaced over the last 20 years were either killed outright by wet exhausts or damaged over time by raw water to the point it was no longer financially logical to fix em up.
The “outright” group were done in by hydraulic lock on startup, and vent loop fault flooding while the “over time” group often had evidence of long term raw water intrusion in or from the heat exchanger, the exhaust manifold the mixer elbow, the vent loop and the aqualock. Some owners return to their boats after an absence and report a flat battery which is often one or two seized pistons caused by the high humidity between the waterlock and whichever exhaust valves are open... turbo’s also suffer badly. Good storage prep can eliminate that nasty surprise.
Some engines fail for no predictable reason, split liners , broken pistons and dropped valves etc and the best maintenance in the world would not have saved them. There was a thread on this forum about a fairly new yanmar that broke a con rod and punched a hole in the block for reasons that even yanmar couldn’t identify.
Ok, enough doom and gloom , but l’ll leave you with a question. How many folks on this thread maintain or check the operation of the anti syphon valve and vent loop or inspect the joint between the mixer elbow and exhaust manifold for corrosion?
Pete.
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Old 25-06-2021, 22:31   #12
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Re: Engines, hours, and brands

we have a pair of 4JH2TE's (1998 vintage) with a tad over 7000 hrs.

they have always been well maintained and we're presently doing oil changes every 150hrs

feel that one reason they are still going smoothly is they get used frequently (boat has been lived aboard full time basically for last 10 years), and used reasonably hard (who said 'diesels love work' ?).

on the otherhand i'm constantly torn by not wishing to push the girls too hard and it's been a long time since they saw their designed max rpm of 3600. 2600 is all i can bring myself to now

but in respect to OP's mention of "tying to figure out why twin outboards are not more common on cats of all sizes actually but especially the smaller cats.", imho outboards are actually quite common on small cats - around here anyway, however reasons why they are not more common include ;

- folk not wishing to carry large quantities of petrol
- inability to get enough traction to get you out of real trouble
- inability to charge batteries effectively
- inability to make hot water

there are reason why outboards are a good thing, but these are what i see as the negatives

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Old 25-06-2021, 22:55   #13
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Re: Engines, hours, and brands

Yes good points, I should have listed the negatives although in my mind those don’t apply to all cruising boats, I’ll propose possibly why.
First I don’t quite understand the fear of petrol, and actually see that as a plus for gennie and dinghy fuel.
Seems like you could size them to get as much traction as needed
A cruising cat would presumably not need to rely on engines for charging and rather they would rely on the solar/gennie grid.
Same goes for hot water.

I agree with you though, a motor used at 2600rpm will always outlast the 3600 one.
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Old 26-06-2021, 02:10   #14
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Re: Engines, hours, and brands

Quote:
Originally Posted by SV WELDER View Post
Yes good points, I should have listed the negatives although in my mind those don’t apply to all cruising boats, I’ll propose possibly why.
First I don’t quite understand the fear of petrol, and actually see that as a plus for gennie and dinghy fuel.

PETROL GO BANG. MORE PETROL = MORE BANG

Seems like you could size them to get as much traction as needed

ITS NOT ONLY A QUESTION OF SIZE, BUT ALSO HOW FAR UNDER WATER THE PROP CAN BE LOCATED

A cruising cat would presumably not need to rely on engines for charging and rather they would rely on the solar/gennie grid.

WE ALL HAVE SOLAR, WIND ETC ETC, BUT O/BOARDS TAKE AWAY ONE OPTION

Same goes for hot water.

ENGINE HW IS A FREE BY PRODUCT. HW VIA ANOTHER SOURCE WILL USE BATTERY (FOR WHICH THERE IS NEVER ENOUGH)

I agree with you though, a motor used at 2600rpm will always outlast the 3600 one.
these above are my personal views. you are welcome to accept or reject as you see fit. a lot depends on your usage. for us (full time cruising live-aboards) outboards do not make sense, for the reasons outlined

cheers,
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Old 26-06-2021, 07:16   #15
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Re: Engines, hours, and brands

In a commercial fishing vessel ( not a sailboat) I have an Isuzu C-240. This a an inline 4cyd 60 hp diesel. I installed it new in 1992 and changed oil every 150 hours (mobile Delvac 15-40). Today it runs great, no smoke and has just over 28,000 hours. I never run it over 1800 rpm or let it idle excessively. I have however rebuilt the fuel injection pump at 21,000 hrs and of course the normal things like a few starters, alternators, water pumps and adjust valves each 3500 hours.
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