Slow You Down

[Paladin]

2 hours ago, grendel said:

surely its down to the rangers to prove intent to speed. a number of the Martham boats I hired didnt even have a rev counter, so the speed you are doing always has to be a subjective judgement, to prove intent to speed for a prosecution, the BA would be required to pprove the boater knew they were speeding- if they dont even have a rev counter on the boat then its going to be mighty difficult for the BA to prove intent- some boats have a rev counter, but nothing else, again, if you are doing the rpm for a certain speed then how are you to know the speed across ground due to the current, I know that 2000 rpm is around 5mph, and that 1600 rpm is around 4mph (ish), but if I was pulled up for 4.2mph they would probably be asked how I can measure .2mph without a speedo and just a rev counter, actually I have a good idea what speed I am doing just by the appearance of the wash.If I have white flecks in the wash I am doing 5mph, if I can barely see a wash I am doing 3, judging 4 is a bit more difficult.

No, intention does not form part of the offence.

The relevant bye law states: "No person, being the navigator of a motor vessel, shall cause or permit such a vessel to be navigated on any stretch of water specified in Schedule 1 to these Byelaws at a speed over the ground greater than that specified in the said Schedule in relation to that stretch of water."

In my experience, the rangers only intervene if the speed is excessive and/or is creating too much wash. They certainly wouldn't bother with the odd 0.2 mph over the limit in isolation.

 

[Smoggy]

If running through somewhere like reedham with the tide they will turn a blind eye to quite a bit over the limit as long as the wash isn't excessive, they will sometimes shout at boats well under the limit if pushing a bow wave against the tide.

[oldgregg]

2 hours ago, rightsaidfred said:

Even a rev counter is subjective depending on hull, engine and prop. At  a 1000rpm I am doing 3-4mph lower than that and I am in neutral, 12-1400 is around 5mph depending on tide and so on, at 2000 I am flying on Braydon with another 300 to spare but doubt that would make a lot of difference with  the hull design, I know from my hiring days and friends the same hull with different configurations of engine and prop behave differently, there is no one size fits all.

You also have the variables of whether the prop is on a shaft, hydraulics (or on some boats V drive, IPS etc) and what the ratio is on the transmission.

Shaft drive boats typically have a ratio of around 2:1 (1000 engine revs = 500 shaft revs) but it varies. Hydraulics will also effectively have a difference between input and output revs (though I don't know what the ratio is) and you then have to factor in probably 20% conversion losses depending on which type the boat has.

[NeilB]

As Vaughan said a lot of hire boats are propped for low speed handling, if run flat out and unresticted the engine will be severely overloaded with reduced lifespan.  
A marine drive line will have a specified rpm range it must meet with the vessel at full displacement, this is recorded on the commissioning report.  If it doesn’t reach the correct rpm the warranty is void.  I very much doubt any Broads hire boats are treated this way but it’s the official line where I work.

[Broads01]

8 hours ago, grendel said:

surely its down to the rangers to prove intent to speed. a number of the Martham boats I hired didnt even have a rev counter, so the speed you are doing always has to be a subjective judgement, to prove intent to speed for a prosecution, the BA would be required to pprove the boater knew they were speeding- if they dont even have a rev counter on the boat then its going to be mighty difficult for the BA to prove intent- some boats have a rev counter, but nothing else, again, if you are doing the rpm for a certain speed then how are you to know the speed across ground due to the current, I know that 2000 rpm is around 5mph, and that 1600 rpm is around 4mph (ish), but if I was pulled up for 4.2mph they would probably be asked how I can measure .2mph without a speedo and just a rev counter, actually I have a good idea what speed I am doing just by the appearance of the wash.If I have white flecks in the wash I am doing 5mph, if I can barely see a wash I am doing 3, judging 4 is a bit more difficult.

I disagree, "ignorance of the law is no defence" as the saying goes. The fact that a boat has no GPS or rev counter doesn't in itself mean speed over ground can't be measured, it just means the boat doesn't happen to be fitted with the means to do so.