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Post by chrisw1311 on Jan 12, 2014 19:04:32 GMT
I have a eolia 24 foot seven inches long, fitted with a yanmar 1gm, i have it moored in Grays on the thames where the tide is particularly strong, i dont have the power to push through the tide when its at its strongest, my engine is fitted with a 12 inch 12-8 two blade, right hand propellor, should i reprop and if so what size would you recommend, also any ideas where i could buy a secondhand prop (Essex area)
I also have a Yanmar 2gm in the garage which i could fit at a later stage if reproping doesnt help, this looks fairly easy apart from probably having to have the prop shaft shortened.
Any suggestions recommendations will be gratefully received
regards
Chris
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Post by sitara on Jan 12, 2014 22:29:04 GMT
Chris,
The size of the propeller is governed by the following. The water line length of the boat which sets maximum hull speed, the displacement of the boat, the available horsepower from the engine (allowing for transmission and bearing losses), the maximum engine RPM and the gear box ratio. Plugging this data into the appropriate formulas will give you the optimum size of propeller for your boat.
I guess the main info that you will need is hull speed for the boat which would be about 6 knots and the strength of the current in the Thames. If the current is near six knots then you will have difficulty pushing into it no matter what prop or engine you have. To get you boat to speeds much greater than hull speed starts using a lot of power as the boat tried to climb the bow wave. A bigger motor and prop would be an advantage when pushing into head winds and significant waves. I lost about 2.5 knots boat speed when pushing into 30 knot head winds a few days ago.
It will pay to get lots of advice before taking on the expense of a new prop or the hassle of replacing the engine and prop. Hope this helps, Rob.
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