Prop Size advice

  • Thread starter Thread starter Guest
  • Start date Start date
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Guest

Guest
I just fitted a new engine and the prop I chose with advise from the engine Manufacture and a prop calculator were both wrong! I need to get the right one does anyone know how I can ensure I choose the correct one? Engine is beta 28hp 2:1 gearbox and ona Westerly SeaHawk 34 ft LWL 28ft.. I have a 14X9 which is far to small, 2000 rpm gets me around 2.5Knts..

Hope someone can help me?

Thanks

Shreck

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G'day Ken.

If you deal with a prop manufacturer, they will swap a prop if it's not what you expected at no cost, having said that, they won't pay for haul out.

I have included some web sites for your information, are looking you looking at fixed, folding or feathering props?

http://www.autoprop.com/

http://www.yanmarhelp.com/Install/prop_clrcs.htm



<hr width=100% size=1>Andavagoodweekend, Old Salt Oz /forums/images/icons/cool.gif
 
Performance indicates something more fundamental than size. Not wishing to patronise but have you got the handing right? When I installed my Beta the hand changed relative to the previous Yanmar.

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Umm, interesting Prop calc gives me around the size you've got fitted as well.
Not being stupid but it is the correct size isn't as I've just had a traumatic prop incident and the prop was no where near the marked size!
I guessed 6 ton, max revx 3,800. As someone else said it sounds fairly fundamental.

<hr width=100% size=1>Jim

Draco 2500
 
IMHO your prop is way undersized.
I had a 15*13 3 bladed prop fitted to my 34ft yacht (6.5 tons) using a Yanmar 3GM engine (21hp). The engine would push the boat at about 6 knots. Reverse was virtually none existent. (I suspect due to thickness of skeg obscuring large part of flow.) At max revs the engine was not struggling.
I changed this last year to a 17x14. This was way oversized with the engine only able to do 1500 revs but reverse was great.
I have just changed it again to a 16x13. This is much better. The engine is much smoother and whilst I still cannot obtain max revs reverse is still usable.
Your boat size and weight sound very similar to mine. You have more hp and consequently I suspect a 16 x 13 is probably closer the mark. (My gearbox ratio if I remember correctly is 2.36:1.)
Others may differ.
If you want to try a 17*14RH 3 blade prop with 1" shaft I can lend you one.

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