Welcome to PD's Jesper

The Swiss Kramer WEB site certainly advertise the Anton Exclusive range of engines, however this morning after reading your post I can open the WEB site but not view any product...possibly they are have WEB issues
You certainly could e-mail Anton directly in France...I found the Kramer site offered better translations & views of the Anton product than the original manufacturer....also interestingly I found the exchange rate from AUD$ to Swiss CHF [Swiss Franc] offered a cheaper alternative to AUD$ to EURO [from Anton]
I have no experience with the Anton product, but many French marine steam groups display many models installed with Anton product & running well
As you plan to progress with the Africa Queen, another WEB site called Model Mayhem offers many threads & postings on the same Africa Queen......each example uses a twin cylinder engine......from memory one example uses the Anton Cristal
Please confirm the scale or overall length of your vessel hull
Single cylinder steaam engines can be problematic in marine applications as dependent on the configuration could be single rotation and non self starting....so it is important you understand these points prior to an new engine purchase
Having said this

I am not suggesting you should not post here on PD's

Many members of PD's are also members of Mayhem............and

post on both sites

So please keep us informed with your thoughts & directions........digital photographs are always welcome ..........Derek