Speeds

Ridgewoodwoody · 08 June 2015, 08:25

I have a 3.3m inflatable powered by a 6hp Yamaha outboard. How do I find out the maximum speed of such an outfit? The reason for asking is that we're taking the boat to Holland soon and I'm informed that I would need a license if my boat is over 15ft and is capable of doing more than 20km p.h. I don't think it is but would be reassured to have definite knowledge. There will be just the two of us on the boat.

Fenlander · 08 June 2015, 08:33

Buy or borrow a GPS/Nav is one way.

I'd make a guess with one light/medium weight person that outfit would plane and exceed 20km/h.

With a couple of heavier people and fuel/kit etc it probably wouldn't exceed displacement speed around 12 km/h.

Pikey Dave · 08 June 2015, 08:35

There's a theoretical maximum based on WOT engine RPM/gearbox ratio/prop pitch, the boat can't exceed this theoretical speed, because there's also "slip" to factor in.
You could buy, beg, steal, borrow a handheld gps & do some practical on-water tests. Not a bad thing to own anyway & can be picked up cheap as chips.
Or you could just make up a number, no-one is going to test it.

What licence do you need? ICC or are you taking it inland on the canals?

PS, your boat is only 10'9" so doesn't exceed 15'

willk · 08 June 2015, 08:54

I'd have thought that the secret here is not to get CAUGHT doing more than 20kph in it! That's about 11 kts - if you can plane that thing at all it will do 11kts.

ShinyShoe · 08 June 2015, 09:01

Smart phone well protected from water. Plenty of APS for other sports like running / cycling that will capture speed data.

mixyblob · 08 June 2015, 10:02

I use the GPS Test App and find it very good/accurate.

piotr · 08 June 2015, 11:14

Quote:

Originally Posted by willk

I'd have thought that the secret here is not to get CAUGHT doing more than 20kph in it! That's about 11 kts - if you can plane that thing at all it will do 11kts.

No, when stopped by the police they will check the max speed of your boat. The fine for not having the correct licence is 550,- euro.

Ps: the length of the boat doesn't matter, if it's capable of doing 20+ kmh you need a licence (ICC Inland Waters) for the large lakes and rivers (i.e. IJsselmeer, Markermeer, Wester Schelde etc) you need ICC Coastal Waters.

More here

Max... · 08 June 2015, 11:31

Just test it with the lightest load with GPS and then wind in the max throttle position on the carb until it is 10% under the max permissible.

Ridgewoodwoody · 08 June 2015, 15:49

Thanks for the advice, everyone. Just out of interest, if one were to buy a larger vessel say a 21ft motor cruiser, are there stautory competances/licenses required to use it on British waterways?

Pikey Dave · 08 June 2015, 16:36

Quote:

Originally Posted by Ridgewoodwoody

Thanks for the advice, everyone. Just out of interest, if one were to buy a larger vessel say a 21ft motor cruiser, are there stautory competances/licenses required to use it on British waterways?

On the sea, no. On inland waterways, yes, but I'm not sure what they are.

Fenlander · 08 June 2015, 17:39

On our Cambridgeshire rivers you would need a licence at about £345/yr and the boat would have to pass a safety check in regard to gas/fuel systems. It would also have to be insured.

Ridgewoodwoody · 08 June 2015, 17:50

Thanks. Could you tell me what is the license and how is it obtained?

Fenlander · 08 June 2015, 17:54

Well this is for our area but I guess yours might be different... https://www.gov.uk/government/upload...0/LIT_6608.pdf