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Old 27 April 2004, 15:34   #11
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Codprawn!
Valid points!
Would the drastic difference in hp between commercial and leisure be due to different prop sizes therefore torque/output varies?
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Old 27 April 2004, 15:38   #12
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Battery box! Yes it is a good idea to keep it dry, but only essential if it's of the un-sealed lead acid type, a sealed gel type batt. will be quite happy to get wet provided that you grease the terminals well (corrosion). The other reason to house your Batt. is to protect it from things you might accidently drop on it, like an Alloy paddle or handle of your boat hook. This could not only physically damage your Batt. but also short out the terminals in worse case causing an explosion.

Good practice to place in a Box and put an Isolater on the top of the box as well, just as good measure.

Hope this helps.

Andy
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Old 27 April 2004, 15:38   #13
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Not knowing much about these things, I would have said it was purley stress to the engine; a 100hp downrated to an 80 for commercial use can be used at WOT for hours without it getting too worn. A 100hp for leasure use running at 100hp for hours would wear out more quickly....
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Old 27 April 2004, 17:23   #14
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Engine wear

undefined
Quote
The higher the revs the more wear there is on the engine - simple


This is simply not true, the higher the engine revs, before redlining doesnt mean more engine wear, If you are not overrevving you are not harming the engine, when it is up to temperature.The higher the engine revs the faster the oil pump delivers oil and lubrication as per required, and coolant, marine engines are rated for constant horsepower afterall.A hard acceleration on a cold engine would be far worse than driving at full rpm.At full revs everything is warmed , oil is flowing , engine is still being cooled and still being lubricated, I would definately feel an engine is more liable to wear when driven hard cold , and immediateely after a start.Do you ever see the smoke out of a Trent or Severn class Lifeboat which are driven hard immediately from a cold start, thats an example of ring and cylinder wear, you are correct to let things warm up and service regulary, but its okay to drive at full rpm, provided you are staying out of the red.
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Old 27 April 2004, 17:30   #15
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Gavin!
What is an aceptable warming up period?

Hightower!
Thanks for the info! I think I might have an isolator which might have been disabled. I'll check it out.
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Old 27 April 2004, 17:45   #16
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Warming up

In the absence of a temp guage, you will hear the difference and feel the difference in a two stroke motor , from cold driving compared to when the motor is warm.I would let the motor idle for maybe less 6/7 mins feel the telltale to know when the motor is warming, there is nothing worse than cold accelerations on a motor
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Old 27 April 2004, 17:48   #17
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Bore wear increases with the square of piston speed (therefore rpm). So the difference between 5000 rpm and 6000rpm is 20% (1.2) , bore wear rate increases by 44% (1.4).

Quote:
Originally Posted by gavin
undefined
Quote
The higher the revs the more wear there is on the engine - simple

This is simply not true, the higher the engine revs, before redlining doesnt mean more engine wear, If you are not overrevving you are not harming the engine, when it is up to temperature.The higher the engine revs the faster the oil pump delivers oil and lubrication as per required, and coolant, marine engines are rated for constant horsepower afterall.A hard acceleration on a cold engine would be far worse than driving at full rpm.At full revs everything is warmed , oil is flowing , engine is still being cooled and still being lubricated, I would definately feel an engine is more liable to wear when driven hard cold , and immediateely after a start.Do you ever see the smoke out of a Trent or Severn class Lifeboat which are driven hard immediately from a cold start, thats an example of ring and cylinder wear, you are correct to let things warm up and service regulary, but its okay to drive at full rpm, provided you are staying out of the red.
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Old 27 April 2004, 17:52   #18
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I'm not 100% sure about this, but I would expect lifeboat engines to be preheated, and probably pre-oiled too. The bigger the engine, the bigger the problem of warming the engine up is as it can take days in big ships. That's why the navy favour gas turbines on many of their ships as they can safely produce full power within a few minutes of spooling up.
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Old 27 April 2004, 21:22   #19
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Quote:
Originally Posted by MadMat
Bore wear increases with the square of piston speed (therefore rpm). So the difference between 5000 rpm and 6000rpm is 20% (1.2) , bore wear rate increases by 44% (1.4).

Thanks for that Mat - I would have thought it was common sense...........
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Old 28 April 2004, 06:02   #20
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Bore wear!

Sorry MADMAT I'm still not entirely convinced of this.
Where did you find out this conclusion?
Conrod off set, size of piston, amount of cylinders, & 2/4 stroke are other factors that may cause more of an effect.

I do agree that sitting on or near the red line for hours on end is not that good for your engine BUT you are MORE likely to damage your engine by starting it & driving off staight away!

As CODPRAWN said 'If you find you are running at WOT for long periods you need a bigger engine! Either that or it's too calm!'
Agree with this also - where's that 90!

Pete
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