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Old 23 August 2007, 16:04   #11
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When I mentioned the Yanks getting 2 - 3,000hrs on their engines I was on about the 2 strokes.....
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Old 23 August 2007, 16:32   #12
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Originally Posted by 9D280 View Post
Most car engines theser days are designed for >150K Miles. Difference here is that you don't do said mileage at WOT!

Having said that I have a 1972 vintage Johnsorude which after the bottom end rebuild (which wouldn't have been needed if the previous owner hadn't introduced it to the bottom quite so often!) is still a "first pull" starter....

I suspect it's one of these things - some people will own the most reliable engine ever built, and the next boat along will have the same engine and nothing but troubles..... It's all dowm to the statistical fun of mating components reliably in mass produced machines - until relatively recently sometimes it's spot on, other times.....
There are some stats on readout from outboards on this forum now which breakdown the Time run against the percentage time at each rev range the time at WOT is minimal,the main drawback is continuous running without a break. In a car this breaks down the protective components in the oil.


The sump on my three litre outboard is 8.5 ltrs (compare that to a 3 ltr car) it is also producing 50 hp per litre so is relatively unstressed.

Changing the oil in a four stroke regularly is in my view critical.
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Old 23 August 2007, 16:42   #13
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Originally Posted by codprawn View Post
When I mentioned the Yanks getting 2 - 3,000hrs on their engines I was on about the 2 strokes.....

So maybe even double that for a 4 stroke then ?


Outboards seem to be in a lower state of tune than car engines and with more constant cooling , faster warm up , and less variation in revs in general I guess they should last longer in most cases .
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Old 23 August 2007, 17:04   #14
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Originally Posted by ian parkes View Post
So maybe even double that for a 4 stroke then ?


Outboards seem to be in a lower state of tune than car engines and with more constant cooling , faster warm up , and less variation in revs in general I guess they should last longer in most cases .
I wouldn't bet on it. The main problem are the emission laws. They tend to run engines leaner than they should which does nothing for the pistons and the bores. I think the early problems with the suzuki 4 strokes was caused by this - a reprog sorted them out - I suspect by making sure the pistons received more cooling fuel.
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Old 23 August 2007, 17:47   #15
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Originally Posted by codprawn View Post
I wouldn't bet on it. The main problem are the emission laws. They tend to run engines leaner than they should which does nothing for the pistons and the bores. I think the early problems with the suzuki 4 strokes was caused by this - a reprog sorted them out - I suspect by making sure the pistons received more cooling fuel.

I agree with that , emissions laws are not helping many engines these days but that goes for all motors not just 4 strokes . I read the other day that the E Tec was gaining emissions aproval somewhere wher 2 strokes had previously been banned

But how many of ever likely to do 2-3000 hrs for pleasure use , in fact not many of us could afford that much fuel , £90 grand at a litre a mile with my math
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Old 23 August 2007, 18:12   #16
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Also Outboards for the whole tend to run in saltwater. So even if the engine doesn't pack up in the conventional sense, other components could make the engine unusable. Such as PTT knackered for whatever reason or wiring totally wet. Even sea water in the fuel could shorten its life. Something that won't happen with a car.
My engine is apperantly a Suzuki Swift engine (Didn't know they did a 2.2 Litre version, but their you go) and I suppose if that was run at 4500 RPM for hours on end it wouldn't last long.
I suppose at the end of the day there are very few outboards that will get hammered like company cars on the motorway all day. But companies that own these cars must know something as in a lot of cases they sell them on after 6 months.
I have owned a 6 month old rental car and it was awful. You could just tell it had been thrashed during its short life.

Anyway back to an old answer of mine. Anyone seen any Trabants or old Skodas knocking about lately ?
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Old 23 August 2007, 18:54   #17
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It is a well known fact that cars that do high miles on regular long journies last considerably longer .
its partly due to the amount of time an engine runs below normal operating temperature

Its harder to drive a boat engine badly , you cant get the wrong gear up hills and make it labour or hold it in a low gear and over rev it for ages .
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Old 23 August 2007, 21:19   #18
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Hey... My boat won't coast....

I believe marine engines have a much harder life than our land based equipment, these motors are constantly under load, no downhlll in a boat, that motor is always working, it never gets a break..
I would think a well cared for motor in a car would outlast a marine engine hour for hour just because of that constant load being a significant operating stress for marine engines versus car or truck motors. You motor experts out there are free to chime in, 2 cents worth, whatever...
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Old 24 August 2007, 05:19   #19
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Low temperatures and high loads

I would imagine that an outboard is run at a significantly lower temperature than optimum due to the limitations of a seawater cooling system. You can't run much higher than about 65C without filling the waterways up with salt.

My outboard tends to run at 45C when at speed and up to about 70C when running slowly. Thermal cycling is bad for engines.

Most cars will be up to 90C within a few minutes of starting and the temperature will be stable.

Also, as said before marine engines are run at much higher loads than car engines. My opti burns about 28-30 litres per hour (as per smartcraft gauges)most of the time i'm using it. 60 litres per hour at WOT - so most of the time i'm runing at 50% load, or 75hp from 2.5 litres displacement.

Have just bought a cable and diagnostic software so I can plug into my car. Observing the airflow into the engine indicates that at motorway cruising speeds indicates that the engine is producing less than 40hp. That's from 2.7 litres displacement - so approximately half the loading of my outboard.

Anyway - outboards almost never wear out - bits drop off long before they have a chance to!
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Old 24 August 2007, 06:21   #20
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Quote:
Originally Posted by ian parkes View Post
...Its harder to drive a boat engine badly , you cant get the wrong gear up hills and make it labour or hold it in a low gear and over rev it for ages .
You should go over to the boat polishers' site, there's ayeways someone breaking 'em.
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