Engine power outputs

[doug748]

Any engine experts out there?
My Petter is rated at 11hp @ 3000rpm
The Beta BZ482 is rated at 13.5hp at 3600rpm
Are these "at the prop" power outputs, or otherwise?
If I change to the Beta will I get a true extra 2.5hp?
Will I get away with the same prop - 13" * 10.5"
Thanks...

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[ongolo]

If you run the beta also at 3000rpm you will not get extra 2.5HP and if you try and increase the revs, your prop might be too big.

I would select the more reliable, easier to repair engine with better parts supply available.

I could calculate the torque and other related data from the revs and HP as there is a fixed relationship between these two and the torque. Whether you need another prop I cannot say unless you give the details of gearbox ratio, pitch and diameter and number of blades and the wheel % of the prop.

Generally, overproping has some advantages if you intend motor sailing.

There will no doubt be other answers coming.
regards ongolo

<hr width=100% size=1>1000 dream about it, 100 talk about it, 10 start and 1 completes it

 

[boatless]

From manufacturer websites, and in the absence of any contrary advice, I'd say that both are rated shaft horsepower. So with identical amounts of friction in gearboxes, you should get what you pay for!

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[ongolo]

An engine manufacturer usually gives DIN or SAE horse power, shaft horse power are only used in the Marine industry and as these engines are probably used in other applications, DIN or SAE rating makes the engine look more powerful and may be easier to sell. Just another swindle.

regards ongolo


<hr width=100% size=1>So what......... it floats

 

[Redmond]

my Petter was rated 11 hp at the engine - and thses engines were never reliably marinised although mone only broke down twice ereparablywhilst at sea and caused one fire.

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