"Only on tick-over."
Dave Morrell comments that a common excuse for speeding past moored craft is "I'm only on tick-over". Unfortunately this could be true in many cases, writes Ian Reid.
Most small marine engines used on the canals are derived from industrial engines. As such they are not usually designed to cover a wide speed range. Typically the tick-over speed might be 1000 rev/min and the maximum speed 3000 rev/min.
Propeller size
The propeller size might be chosen to give, let us say, 6mph on rivers at a non-earsplitting 2000 rev/min from the engine. This would give a bit of speed in reserve if required; but that would depend on whether the engine could produce adequate power.
But what happens at tick-over? 1000 is half 2000 so the boat speed would be half 6mph, ie: 3mph. In other words the boat won't go slow enough for any fine manœuvring. Don't tell the steerer to knock it out of gear; that way the steering is all but lost. As 3 mph can create quite a bow wave on silted up canals there will be particularly loud moans from those with slackly moored boats.
Alternatives
The answer might be to use the wider range of speeds available from automotive engines, but the satisfying throb we are used to would be lost. Otherwise a hydraulic drive should be able to achieve slow output speeds. An alternative which I haven't seen for years would be a gear box with a lower gear for slow speed use. This wasn't uncommon in the days before Elfin Safety ruled, when converted petrol engines from ancient Ford Populars or Austin Sevens were used complete with their original gearboxes. A relatively simple conversion gave two very useful forward gears and one reverse. They were a delight to use and could come slowly into moorings under full steerage control.
Those were the days! They were also the days when real boaters, born and brought up on the cut were still around and not in the habit of slowing for moored craft in silly places (their words, not mine).