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Old 14 October 2004, 08:04   #31
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Cookee and who ever is intested I just found this thread I was talking about with the broken Falcon prop BAY TO BAY RACE South AfricaHave a look at it if you like
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Old 14 October 2004, 17:34   #32
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Quote:
Originally Posted by John Kennett
..there's no way any manufacturer is going to understate the output of their engines . . .
Yes they do.
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Old 14 October 2004, 19:51   #33
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getting back to the original question ....then what about a fantum evo
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Old 15 October 2004, 04:25   #34
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Yes they do.
Who?
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Old 15 October 2004, 07:34   #35
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Yanmar 300? Actually 315hp??
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Old 15 October 2004, 07:53   #36
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Yanmar 300? Actually 315hp??
I've often wondered about that one, it seemed to change overnight. Barrus must have got a new batch of stickers coz as far as I'm aware the motors are the same spec!
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Old 15 October 2004, 07:53   #37
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I think it's fairly standard practise, JK. The info. I have is considerably out of date now but I'm sure it'll still be indicative.

These are the results of dyno tests on standard engines:

OMC 150 ..............155 @ 5000
OMC 150GT & XP ...175 @ 5250

Merc 225 ...............225 @ 6000
Merc 200 ...............220 @ 5750
Merc 175 ...............195 @ 5750
Merc 150 ...............165 @ 5750

Yam 225 ................250 @ 5750
Yam 200 ................220 @ 5500
Yam 150 ................160 @ 5250


It certainly accounts for the differing performances of various makes of engine on similar boats. After all, 200hp is 200hp and all boats, if rigged properly, would give the same or, at least, similar top speed with the same engine power.

This, of course, doesn't take into consideration mid range power and, therefore, the actual drivability of a particular boat/engine combination.

----------------

Just as an addition, for information. Except for an increase in engine capacity, the only engine modification which will give increased power over the whole of the rev. range is an increase in compression ratio. Generally, mods give extra power at increased engine revs. Note the word 'generally' because this is not necessarily a fixed rule.

Oh yeh, a higher compression ratio will also give a better fuel consumption. Just though you'd like to know that.
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Old 15 October 2004, 08:03   #38
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where is "horsepower" measured in these tests, JW, are they crank ratings or prop ratings? If crank, did they establish transmission losses? I notice that Yanmar rate their engine from 250 ish up to 315 depending on inlet temperature. Also they give a continous rating as well. Any idea what the inlet temperature is under normal running conditions installed in a boat?
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Old 15 October 2004, 08:17   #39
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The literature refers to an absorption brake powerhead dyno so I guess they are powerhead figures. I believe them to be comparative tests but no indication of air temp or air pressure is given.

Jono, these are all outboard motors, are you referring to a diesel?

Temp in a boat is going to vary with the engine housing design and how much heat is collected by the air passing over various components on its way to the airbox. The engine block temp is going to be very close to the engine water temp. I guess various ancillaries may reach substantially high temps.
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Old 15 October 2004, 08:42   #40
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Sorry, JW, I should have separated out my post a little better..

Yanmar "315" engine is only rated at 40 C at the injector. I just wanted to know what a standard operating temperature was in this region. I know you have the heat soak effect raising the temperature but you also have the cooling effect of the fuel passing through the injector, so what would the temperature be. it strikes me as a strange way to quantify power rating. I mean, I understand that dirty 'ol diesels ( ) produce their max power when cold, but do they reach 40 C in normal operating conditions?

As for the outboards, if we take transmission losses into account are we more in line with what the engines are "badged" at?
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