disposable engines???

[Silent Lady]

7500 Hours

We had a charter boat the other year with 7500 hours and it was running superbly Beneteau 323 with Yanmar 3ym20

 

[Ubergeekian]

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.

I have spent a fair amount of time being aerotowed by small Lycomings. That's a hard life: full welly at low speed for eight minutes followed by the fastest dive at idle back to ground which the heads can stand.

 

[Ubergeekian]

Entirely the other way round: car engines regularly get revved and worked to go up hills, accelerate away from lights, etc.

Even then they are rarely asked to produce anything like full power. My little Nissan Micra can easily keep up in normal traffic with cars which have four times as much power available. Full throttle is very, very rarely used in normal driving.

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.

The engines which survive 150,000 miles are generally the ones with easy long distance high speed lives. But yes, "at least 2,500" would have been better.

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.

I was thinking of making that point but checked the list of Volvo Penta engines and decided that it didn't really stand up.

For example, out of their 5 cylinder 2.4 litre diesel they get anything from 107 bhp (45 bhp/l) to 213 bhp (89 bhp/l), which seems fairly close to what they get out of the road-going equivalents.

And I stick to my claim: a 100bhp marine diesel is likely to spend most of its life at 80bhp while a 100bhp car diesel is likely to spend hardly any time at more than 50bhp.

 

[alant]

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.

What "high powers" do you run your revs at?

2000-2500 seems ok on my car diesel & don't normally run my boats any higher.

 

[Tranona]

For example, out of their 5 cylinder 2.4 litre diesel they get anything from 107 bhp (45 bhp/l) to 213 bhp (89 bhp/l), which seems fairly close to what they get out of the road-going equivalents.

And I stick to my claim: a 100bhp marine diesel is likely to spend most of its life at 80bhp while a 100bhp car diesel is likely to spend hardly any time at more than 50bhp.

But that is not relevant to most small yacht auxilliaries. Kubota (Beta and Nanni) small engines are 479cc with outputs of 10 or 13.5. A 38hp has 1498cc. So specific outputs of between 20 and 25hp per litre maximum. Run at 75% means using 15-18hp per litre. Almost "vintage" outputs!

 

[Ubergeekian]

What "high powers" do you run your revs at?

2000-2500 seems ok on my car diesel & don't normally run my boats any higher.

Speed is only part of it. Stick your foot down in the car and you get a huge increase in power without - initially - any increase in speed.

 

[Heckler]

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.

Just a thought to chuck in to the equation. Weekend before last I took Sacha to Milford Haven from Pwllheli. Hardly any wind so motored all the way. Logged 17 hours on my NEW hourmeter.
I kept it at 2000 revs except for the 2 odd hours spent stooging around in Whitesands Bay waiting for the tide.
My Peugeot 406 cruises comfortably at 2000 rpm and does about 70mph. So if you multiply 17 hours by 70 mph it gives 1190 miles. Sachas engine did the equivalent of 1190 miles that weekend.
At the average annual hours most often quoted for a boat engine of 150, that gives a mileage of 10500 per annum
So a 5 year old engine will have done well over 50k miles in less than optimum conditions.
Food for thought?
Stu

 

[Ubergeekian]

My Peugeot 406 cruises comfortably at 2000 rpm and does about 70mph. So if you multiply 17 hours by 70 mph it gives 1190 miles. Sachas engine did the equivalent of 1190 miles that weekend.

Remember, though, that your car is probably running at 20 - 30% of full power while cruising at 70mph, while Sacha is probably at 80% or so.

 

[ProDave]

The engines which survive 150,000 miles are generally the ones with easy long distance high speed lives. But yes, "at least 2,500" would have been better.

I drive a Subaru, and my present car has done 120,000 miles. The two before did over 160,000 and I only traded up as they were getting old and rusty, not because the engine was failing. We have just sold an 18 year old VW golf with 180,000 miles on the clock, still running well, but the bodywork was getting rough.

These days, it's not a question of an engine which "survives 150,000 miles" that's pretty much the norm. I would be very very dissapointed with modern cars if the engine was not good for 200,000 miles.

 

[vyv_cox]

We had a charter boat the other year with 7500 hours and it was running superbly Beneteau 323 with Yanmar 3ym20

I know of a couple of Yanmar 3GM engines in charter company flotilla lead boats that have done over 15,000 hours with no attention other than routine maintenance. Both run perfectly, smooth and reasonably quiet, and start well.

One of the big differences between car and boat hours, according to Yanmar, is that boat ones are mostly at constant speed. The varying revs of car driving help considerably in longevity.

There is information on bore glazing on my website at http://coxengineering.co.uk/bore.aspx It isn't complete yet but I hope what is there might be useful.

 

[westernman]

Remember, though, that your car is probably running at 20 - 30% of full power while cruising at 70mph, while Sacha is probably at 80% or so.

Motorway driving is the most undemanding use for a car.
However, a typical car will probably average around about 20mph during its lifetime, with a lot of stop start driving.

This is why sometimes a high mileage sales reps car which has been thrashed up and down the motorway is a better bet than a low mileage old grannies car which has never exceed 20mph in its life and has done only short trips and has never been fully warmed up.

 

[Avocet]

Is it just me or are we missing the point? My 12hp single cylinder (about 400cc, I think) is getting on for 30 years old. It's going to be killed off by rust eating through the head casting, ultimately. The anodes keep it at bay, but ultimately, I'm sure I'll throw away perfectly serviceable internals.

 

[Poignard]

A few years ago, whilst phoning Al at BUKH [UK] Ltd to order something, I bemoaned the news that the DV10ME was no longer being made.

'What will I do when my 25-year old one needs replacing?' says I.

'It won't' says Al.

I like a man who has confidence in his company's products

(Not sure that applies to ROCNA's snake-oil salesman, though!)

 

[Spyro]

. 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.

This is what I always thought and wondered if this is the case how come we don't get glazing of the bores on our diesel cars?

 

[Dockhead]

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.

Quite. My long term average speed in my motorcar according to the on board computer is 21km/h since new. That's 13mph. That does not consider time idling as far as I know. I live in a giant metropolis with horrible traffic so maybe not entirely typical. But at least a couple times a week the car is used on motorways at speeds up to 100mph, so it's not all standing in traffic jams by any means. 150,000 miles on that regime would be 11,538 hours.

I'll bet that your average speed in your motorcar is a lot less than you think.

And a motorcar engine is, as jwilson correctly pointed out, rather higher stressed than a boat engine, in terms of specific output. And motorcar engines spend a lot of time idling and working at lower loads and lower RPM's than many of us think are permissable for diesel engines.

So I think the difference in life we expect from marine engines comes down to disuse and neglect. It's a big plus to the useful life of motorcar engines that they are used more or less every day. While our yacht engines are expected to crank up and take us out into the Solent without complaint after sitting for a week or five, only to be shut right back down again after we raise sail, having hardly had a chance to warm up. I think THAT's what kills them at relatively low hours, personally.

 

[Dockhead]

But that is not relevant to most small yacht auxilliaries. Kubota (Beta and Nanni) small engines are 479cc with outputs of 10 or 13.5. A 38hp has 1498cc. So specific outputs of between 20 and 25hp per litre maximum. Run at 75% means using 15-18hp per litre. Almost "vintage" outputs!

Not always so. My Yanmar 4JH3 HTE gets 100 bhp out of 1,995cc. The same block and head are used for for differents variants putting out between 56 bhp to 125bhp. So I would be cautious with that generalization. Turbocharging and intercooling can wring quite a bit of specific output out of a relatively primitive marine engine. There is a big range in specific outputs these days.

 

[Signed Out]

A few years ago, whilst phoning Al at BUKH [UK] Ltd to order something, I bemoaned the news that the DV10ME was no longer being made.

'What will I do when my 25-year old one needs replacing?' says I.

'It won't' says Al.

I like a man who has confidence in his company's products

(Not sure that applies to ROCNA's snake-oil salesman, though!)

And probably why they aren't made any more. Nothing like a bit of built-in-obsolescence to keep the market moving.

 

[angelsson]

Problems at 250 hours must be the exception rather than the norm. Plenty of 30 year old marine diesels still chugging away.

Mine for example, original 1972 installation, Perkins 4108, starts quickly, no smoke, loses no oil between changes, which I do more frequently than recommended realising clean oil is a diesels lifeblood, along with filters of course.
Had the usual failures of course, water pump, change of alternator, but she runs sweet as a nut.

 

[Tranona]

Not always so. My Yanmar 4JH3 HTE gets 100 bhp out of 1,995cc. The same block and head are used for for differents variants putting out between 56 bhp to 125bhp. So I would be cautious with that generalization. Turbocharging and intercooling can wring quite a bit of specific output out of a relatively primitive marine engine. There is a big range in specific outputs these days.

I agree, but it is not true of the under 40hp sizes (most popular in yachts). Not one of these is turbocharged - indeed the only model that was, the 2003T was very short lived.

Most of the small engines are derived from industrial diesels more used to dump trucks and diggers, generators etc. which have very different operating cycles from automotive derived engines.

The original example that started this thread was probably of this type - and almost certainly too powerful for the boat, so never run in the way it was designed. It is a common mistake now for people re-engining older boats to fit an oversized engine in the mistaken belief that a "bit more power" is a good thing. Helped of course by the small price (and bulk) differential between say a 14hp and a 20hp. Both will fit in the same space as an older 10 or 12hp, but in many cases the 20 will reach hull speed at 70% power so the extra is never used and the engine is run at 40% power at cruising speed. Add to that the operating pattern of low hours at each run and low hours overall and you have a recipe for short life.

 

[Norman_E]

Not always so. My Yanmar 4JH3 HTE gets 100 bhp out of 1,995cc. The same block and head are used for for differents variants putting out between 56 bhp to 125bhp. So I would be cautious with that generalization. Turbocharging and intercooling can wring quite a bit of specific output out of a relatively primitive marine engine. There is a big range in specific outputs these days.

I have the 88bhp version of that, now with just over 5000 hours and going well. I have seen others with over 7500 hours on them. Mine is rated at max revs 3600, max contiuous revs 3400, and I usually cruise it at 2500, but every so often I give a few minutes at high revs just to avoid glazed bores or to punch against a strong headwind. I think it would be pretty hard to wear one out. As I average 100 hours or less per year I think it will last till I am 100! The key is regular oil changes.