disposable engines???

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fatsailorgit

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I,m confused, just read PBO, re readers engine trouble at 250 engine hours.
my landrover diesel has done one hundred and seventy thousand miles with very little maintenance. how come boat diesels are so fragile? are we all being ripped off or am I missing something?
 
Is this the engine that had 'glazed bores'? As I understand it diesel engines like to be driven hard and if they are only lightly loaded( if you only use it for charging batteries for instance) then the bores do not bed in correctly and become glazed and loose compression. Or if you only run a large engine at low speed under low load. Or if they have been run at constant speed with a light load, like a generator. There has been a lot of dispute/discussion on these forums in the past.
I must be honest and say that I fitted a new engine a few years ago and never had a problem, and I don't know of any problem engines personally.
 
Lack of regular use I suspect. Also a tendency to run them for short periods esp starting and stopping again immediately to make sure all is well during winter lay ups.

Modern car engines probably wont have reached their first service interval in 250 hours.. esp petrol engines.
 
The motor boat forum regularly has people asking for advice on used boats and being told that - to quote a recent one - 75 hours on the engine is a bit much.

Modern car diesels should be good for at least 150,000 miles with regular servicing, which is probably around 2,500 hours. On the other hand, car engines spend most of their time running at perhaps 20% of maximum output and only get wellied occasionally. Boat engines - like aeroplane engines - spend a lot more time at high powers and so might be expected to wear out faster.
 
Vehicle engines are mostly run up every day and surrounded by warm dry air (mostly). Marine engines are seldom run so regularly and then only for short periods (if we're considering aux engines in sailing boats). They live in cold, damp, salt laden air, often with fresh and salt water leaking on top of them. It's a hard life and most of them survive after a fashion.

I can do 4 top end overhauls on my 42 year old Morris Minor for the cost of a head gasket on my Yanmar 1GM10. It's predecessor, a Volvo MD1b was replaced as it was uneconomical to repair (re-bore and top end overhaul) even if all the parts had been available. I could have had an exhaust manifold and a water injection u-bend made up, but it was less bother and only slightly more expensive to re-engine.
 
75 hours on a mobo engine "a bit much". I struggle to do 75 hours a year on my yacht but the engine IS the auxhilary. Even a relatively slow mobo ought to be able to make Cherbourg from the Solent in ten hours or so but I really would expect a motor cruiser to log around that in a year, unless it's a marina-based cottage.
 
Ha, Bought a 5 year old engine last year with 7000hrs on it, Started on the sleepers outside first pick after a year standing there under tarps, Had an overhall after to make sure all was good inside, Perfect bores etc, just got valves ground and turbo recon as a matter of process, Goes lovely, like new, I've heard of trucks out there with up to a million hours and only after minor rebuilds, Boat engines, besides the dampness run in a clean enviroment, no dust etc to wear them out, They should last a very long time if looked after.
 
Suspect this installation is wrong with an engine far too big for the boat. It is a Contessa 26 and the owner refers to his new engine being several hp larger than the old one, which suggests probably a 16hp which is way too much. Add to that running at low speeds (because it does not need the power) and for short periods (because it is a sailing boat) leads to glazed bores and short life. On the other hand if an engine is sized correctly and run hard (at 75% power cruising) it will last a long time. My Volvo 2030 has over 3000 hours on it in 10 years. The Yanmar 1GM in another boat went 19 years and is now in yet another boat, still running as good as when it was new.
 
Topcat47 said:
75 hours on a mobo engine "a bit much". I struggle to do 75 hours a year on my yacht but the engine IS the auxhilary. Even a relatively slow mobo ought to be able to make Cherbourg from the Solent in ten hours or so but I really would expect a motor cruiser to log around that in a year, unless it's a marina-based cottage.
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It was the motorboat forum. They generally worry more about the scatter cushions than the vulgar mechanical bits there. And Cherbourg is full of foreigners so is Right Out. :eek:
 
Ubergeekian said:
It was the motorboat forum. They generally worry more about the scatter cushions than the vulgar mechanical bits there. And Cherbourg is full of foreigners so is Right Out. :eek:
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And even the wealthy must wince a bit at the amount of fuel they use. Anyway 5 return trips a year to Cherbourg is less than 100 hours. Mind you, having watched the Smugglers tonight on telly a few kilos of Golden Virginia will help with the cost!
 
VicS said:
Lack of regular use I suspect. Also a tendency to run them for short periods esp starting and stopping again immediately to make sure all is well during winter lay ups.

Modern car engines probably wont have reached their first service interval in 250 hours.. esp petrol engines.
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My modern diesel car engine asks for its oil change about every 16000 kms.
My average speed is 32km/h. That works out to 500 hours. It is just coming up for its a service now at 128000 (i.e. about 4000 hours).

Yanmar boast that their engines are good for 10000 hours. I doubt many raggies do more than 200 hours in a year. The engine should last more than 50 years.

I think very few boat engines really wear out - they die from neglect.
 
As a bit of an aside ......

5000 hours = 300 000 minutes, at an average of say 1500 rpm each of the pistons has gone up and down 450 million times.

My engine is getting on for about 600 million strokes and still runs sweetly.

Pretty good going considering the abuse it gets! ( hot, cold, salt and a mini explosion for every second stroke! )
 
Ubergeekian said:
Boat engines - like aeroplane engines - spend a lot more time at high powers and so might be expected to wear out faster.
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Small piston aero-engines, like the Lycomings used just about everywhere, have a design life between major overhaul of up to 2200 hours. Where they are used in helicopters (for example Robinsons) they are thrashed within a few percent of their maximum allowed for their whole life between startup and shutdown.
 
Ubergeekian said:
The motor boat forum regularly has people asking for advice on used boats and being told that - to quote a recent one - 75 hours on the engine is a bit much.

Modern car diesels should be good for at least 150,000 miles with regular servicing, which is probably around 2,500 hours. On the other hand, car engines spend most of their time running at perhaps 20% of maximum output and only get wellied occasionally. Boat engines - like aeroplane engines - spend a lot more time at high powers and so might be expected to wear out faster.
Click to expand...

Entirely the other way round: car engines regularly get revved and worked to go up hills, accelerate away from lights, etc. The usual ones that give trouble are the ones owned by people who only take them a mile or two to the shops, or drive them out of the garage to polish them and then back in twice a week.

Similarly, the boat engines that give trouble or have a short life tend to be the ones that are under-worked - lots of low revs, charging batteries, short run times, etc.

150,000 miles on a car engine is more like 5,000 hours than 2,500, unless the car never gets into a city or onto the M25 at rush hour. And car engines are much more highy stressed than boat engines, typically producing at least 60-80 hp per 1000 cc - boat engines seem to be about 20-25 hp per 1,000 cc.
 
fatsailorgit said:
I,m confused, just read PBO, re readers engine trouble at 250 engine hours.
my landrover diesel has done one hundred and seventy thousand miles with very little maintenance. how come boat diesels are so fragile? are we all being ripped off or am I missing something?
Click to expand...
Just had another thought on engine hours - drive across the midwest of the USA and you used to see plenty of old Chevrolet V8s running non-stop week in week out at mid-revs, pumping irrigation water to the fields. They got this usage after the car or pickup they came out of rusted away...
 
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