What's the speed limit?
On our network the speed limit on most canals is 4 miles per hour and on most rivers it's a bit higher at 6 miles per hour, but speed isn't the only factor you need to consider. It's highly unlikely that you would ever pass moored craft at the maximum speed limit.
To judge if you are doing an appropriate speed you need to check your 'wash', which is the waves your boat is creating as it moves through the water. How much wash you're creating will be a combination of water depth, the shape of your boat and the waterway's banks.
A hard-edged bank that's been piled will reflect your wash much more than a soft edge with reeds. Higher speeds in shallow water will create more wash and will drag the propeller closer to the bottom, increasing the chance of fouling.
Short and wide boats will create more wash than long and narrow. The shape of the swim on a boat can affect how much wash is created. Some boats are capable of higher speeds with less wash purely because of their hull design. The smaller the 'scend', the slower you need to go.
Mind your wash
You should never travel with a breaking wash, as this can erode the banks and also harm wildlife. Every year we get complaints about water fowl nests, eggs and very young chicks being destroyed by speeding boats.
When approaching moored boats, slow down and check your wash. You should aim to pass the moored boats with the minimum of water disturbance.
Check your wash some distance away from the moored craft and throttle back in good time. Some people like to pass at tick over and some find they might have to briefly put the boat into neutral, but whatever you do, make sure it's gentle and that you have some steerage.
Moor up properly
The flip side of passing moored boats gently is making sure that your boat is not going to bounce around or come adrift if you are moored up.
Using spring lines can really help reduce the amount the boat will move when another boat goes past. Take care if using mooring pins in soft ground, as they can easily be pulled out. Some people recommend double pinning or using ground anchors. Others are advocates of mud-weights, especially on rivers.