On 03/05/10 21:55, dennis wolfe wrote:
Back when my boat was powered by a petrol 2 stroke it didn't have reverse at all. It had a clutch and throttle, no gear box. (Direct drive off a 2 cylinder 2 stroke).The first Sevcon PMAC I had (bought Summer 07) would not go into reverse until it sensed the prop had stopped turning forward. In my slippery launch this could take up to 15 seconds coasting down from full speed. Could be pretty scary waiting for the 'brakes' to kick in! Others reported this same issue.
Thus I learned to operate 750kg 5m 'launch' with no effective brakes as there was no reverse gear.
Turns out it was possible to reverse - by getting the engine to run in reverse. Throttle down to idle, loosen the magneto, press magneto shorting switch (carefully :-), turn magneto 15" to other 'dent', release shorting switch. If you got it right, the engine would fire out of time and reverse direction. (Most of the time you would just stall, it took some practice).
Even with practice, it you couldn't do it fast enough to use as a braking method and I hate to think what stress the sudden reverse of direction was putting on the crank shaft.
Being able to flip my electric motor almost instantly into reverse is heaven compared to the 'old way' although out of habit I tend to come in so slowly I don't really need reverse power.
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