Hello Brian,
some years ago I had the same question like you. I wanted a boat for using the inland waterways and canals in Europe, owner operated by a couple with the possibility of the occasional 2 more guests in a separate cabin with ensuite bath. Comfortable for onboard living for some weeks and capable and sized for traveling from the Swedish islands down to the Med (via inland waterways). I was open to all materials, propulsion systems, designs and sizes. The only design feature which was set, was the choice for a full displacement yacht, because of volume, comfort, speed limits and economy.
By order of the Admiral, I started a serious and deep research. Because of my lack of experience with inland motor boating, I hired additionally a professional small yacht engineer for an independent and open research of this subject.
We both came to the almost same result. And our result was nothing new. The wheel was already invented
. The exact same type of boat was built in Holland by many yards, because it is the most practical design for the European inland and costal waters and its corresponding laws and regulations.
This was the result:
Material:
Steel and undoubtedly only Steel. Because of the many locks and sloping riverbanks with rocks and the many sheet pile walls, Steel with a solid rubber running strake. Anything else would not have lasted very long.
Hull Design: Multi chine full displacement hull with frames and stringers for volume and stability, because stabilizers were not concidered suitable for the sloped riverbanks.
Maximum size and technical data: Maximum length 14,99 meter (length because of licence requirements) x 4,8 meters width x 1,5 meter draft and 4 meter airdraft (3,5 meter with mast and windscreen down for the bridges and canal tunnels in France). Displacement max. 30 to 32 metric tons. because of the capacity of the haul out lifts in the inland boat shops in Europe. Twin engine diesel of 150 to 180 HP each with prop and shaft plus 24 volt electrical or hydraulical bow and stern thruster. Fuel capacity for 1000 NM range at 8 Kts, potable water for one week for two people plus watermaker. 8 KVA diesel genset, diesel central water heating, air conditioning, electrical cooking, no gas, no petrol store.
And thats the way they all looked like. Aft owner cabin with ensuite bath and owner office with raised aft deck above, two steering positions, one on the aft deck, one in the salon. Engine room under salon, galley forward of salon with additional dinette and foreward guest cabin with ensuite bath. This type of boat is build only in the Netherlands but by more than two dozend of high quality yards. These boats last for ever but are an investment between 650.000,- and 2.000.000,- US $ depending on luxury and options build in. Built time one year.
In order to confirm our research, we chartered one for two weeks in the Netherlands and found all results correct and confirmed and bought one.
But and there is a big but. Our children found slow boating on inland water ways f...... booooooring and
never joined us and they never used the boat themself. We never had the time to go down to France or through the Göta Canal with it. It was and is only used in northern Germany and the Netherlands and selling it would be an enormous loss. So it is still in the family and sits 8 month a year in a hangar on the hard.
Answering your question: A pure displacement motorboat for slow boating on the canals is a non starter, period.
Below the European inland motor cruiser !