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Old 10 June 2016, 11:31   #11
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Also bear in mind the diameter of the prop also affects the RPM......


FWIW, I'm 60Hp, 5m and the difference in literally a tap or two of the trim switch can make or loose 4 knots.

E.G on Monday I had it running at something like 4800 rpm, getting about 20 knts. I trimmed up a tiny amount, didn't move the throttle, and next thing I'm doing 5300rpm, 25 knots and throttled back a bit for a quieter / more economic run!



If you were going with the tide on Etive shouldn't you have been doing about 108 knots?
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Old 10 June 2016, 12:43   #12
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i remembered to check the prop when i was over at the boat doing some bits an bobs to it and the prop is 12.5 x 19 so the 32 knots i was getting out of it isn't that far off the mark to be honest i was quite happy with this as its fast enough
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Old 11 June 2016, 04:06   #13
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To check speed accurately you need to go in opposite directions and take the average 👍
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