Eventide 27 hull speed

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Eventide 27 hull speed

Postby johnwatt » Wed July 9th, 2008, 4:16 pm

Hi all, I sail on a 27 foot eventide 'Beti Wynn'. Im not too sure if the engine is running as it should. We have a Yanmar 1gm10 fitted which will push the boat along at around 4 1/2 knots though it sometimes struggles into the wind. Anybody know if this is about right or should i be getting more speed?

Thanks in advance


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Postby helenrose » Wed July 9th, 2008, 7:03 pm

hi john,

Welcome to the forum,There is a formular for working out the max hull speed but for the life of me i cant remember it,someone will post it on here soon i`m sure, is the boat new to you and in the past did it go faster?but on flat water with no wind i would expect close on six knots,but there a few other factors such as how clean is your bottom? condition of engine, correct prop fitted. hope this helps,


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Postby johnwatt » Thu July 10th, 2008, 2:47 pm

Hi, thanks for you reply. Yeah i've heard about the formula but again cant remember it. I don't actually own the boat just skipper her fairly often, the owner says he was gettin around six knots before which is the reason i query this. i have had a good look over the engine and can't find anything obiously wrong and the prop has never been changed and is in good condition. Also the bottom was cleaned this winter just past so the problem isn't there. think i might have to have a more thourgh look at the engine, im thinking maybe a fuel/air related problem as the last 30 deg travel on the throttle doesnt seem to affect the engine.

Thanks again


chris s
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Postby chris s » Thu July 10th, 2008, 4:13 pm

I think the formula is 1.6 times the square root of the waterline length :lol:

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Postby johnwatt » Fri July 11th, 2008, 4:04 pm

Hi again all, thanks for your replys. managed to get the problem sorted after a further look at the engine. checked the valve clearances and found the inlet valve was around 4mm :!: rather than 0.2mm. slight adjustment and its running great pushing at around 6 1/2, 7 knots.

Thanks for your help


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Fiddler's Green
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speed formula

Postby Fiddler's Green » Wed September 17th, 2008, 1:24 pm

Glad you fixed the problem, try square root of waterline in feet divided by 1.3 .

An Eventide 24 works out at 5.5 knots an E 26 just over 6 knots

It also equates with length of WL in metres, equals speed in knots and hp needed to achive it..... in still water with no wind.

Works for boats up to 30 ft odd.

top speed of my Eventide, a stretched 26... it is 27'3" is 6.75 under sail, yes, done it once!!! Frightened the crew....

6 knots under power because of drag of keels etc... do that regularly at beginging of season, one bit of slime and we are down to 5.5!

Proud owner and builder of 'Fiddler's Green'

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