340 HP? And this is a trailerable boat?
In general, there are speed limits on Swiss lakes - 40Km/h. The rules may be slightly different for (part of) the lake(s) in the italian part of CH.
The boat has to be at least CE/6 certified ( including no bilge water into the lakes), and many others.
In addition, the boat engine has to have strict emissions and noise checks.
It is best to check with the lake authorities on all the requirements. They can and are required to provide you with full and complete information.
Since 2009, boating license in CH has been standardized. The same license is applicable to all lakes in CH. To get the license, one has to pass a written test and a driving/sailing test. The written test can be taken in English, German, French and Italian. Offices in major cities (Bern, Geneva, Basel, Zurich, etc) administer the test in english. There are a total of 60 questions. To pass, one has to correctly answer 56 questions. I recommend the CD at http://www.click-me.ch/en/produkte/theoriekurs.html . The english is not good (it is swinglish), but understandable. The webiste www.click-me.ch also has practice tests (with answers) on line and on CD. I strongly recommend this CD also.
The motor boat practical test will include man overboard skill, parallel parking skills on port and on starboard side, reverse parking skill, various types of knots, and your general knowledge of the boat. They also like to see that you know how to read a compass and local charts so you can read your current location manage to go to the nearest port (assuming it is foggy and/or sudden storm warning). But in general, this last part is on a very high level.
If you have
a) the docking/mooring area organized,
b) formal and original documentation from the manufacturers (boat and engine) that they are compliant with the relevant local and CH regulations
or
c) documentation from a CH boat builder certifying that the company has made the boat compliant with the specified CH and local regulations
d) documentation from a CH boat engine dealer/garage that the company has made the boat engine compliant with specified CH and local regulations,
then you should be able to get a temporary permit (2 letter and 4 numbers) to put the boat into the water. Then the lake police will come, test drive and certify the boat.
Be aware that not all engines can be made compliant with CH regulations. Many fuel injected engines can be, but not all.
They have some weird regulations etc around electrical connections, generators and relevant (electrical) fire supressing equipment. The lake police can also provide you with details of what is required. There are electricians who can provide you with, equipment, installation, and the certifications that the lake police will want to see.
The boat ID (2 letters and 4 numbers) has to be mounted on the port and starboard side of the bow. They have special requirements for visibility purposes. A local print shop can print them for you or find someone who can. Similar prints from co-op bauhobby etc is not acceptable.
You must have some emergency equipment and other things on the boat (like tool box, etc). The lake authorities can also provide you what you need to get. The medical emergency kit is the same as the one you are required to carry in a car - no need to get a one from a boat shop and pay the $$$.
You have to pay tax on the boat every year, just like a car. Once it is paid, you get a vegniette that needs to be applied on the port and starboard side of the bow.
Boats have to be inspected every 3 years by thelake authorities. This includes the boat and the engine (noise and emissions). I believe the electrical components need to be tested and certified every 10 years.
Good luck.
Regards,