We had an Eberspächer Airtronic D5 installed in La Rochelle three years ago. This is the brand and model Amel ordinarily installed on SM's where the buyer requested heating.
This install is easy on many SMs that were originally sold to the U.S. customers because if I understand correctly many of these Amels had a bunch of options included as standard. The valuable factiry option here is "forced air ventilation". Of course any number of Euroland boats also checked this option at build time, but, critically, not all.
If your boat has "forced air ventilation", the installation is not quite trivial, but "light". The furnace is hung from the ceiling of the long cockpit portside locker, exactly replacing the two 24V fans installed there by the factory. In this case, all the ducting to the forward, main and aft cabins obviously already exists. The main additions are:
(1) The Eberspächer temperature sensor to be added on the port side of the dining table, above the oval cubbyhole, right on the mahogany.
(2) The furnace exhaust escape, where your hull will be breached on the port side, at the level of the sole of the long port locker
(3) The fuel pump, which will tap somewhere around the racor filters and run diagonally and upward towards port
(4) A bit of the ducting inside the long port locker should be upgraded to heater-rated ducting. I guess you should change all of the ducting from the original thin-Amel-factory stuff, but we did not, and the boat has yet to catch on fire.
(5) The Eberspächer controller needs be installed somewhere. We put in on the galley's aft bulkhead, inward of the watermaker controls. Some people put it on the removable piece of wood outward of the 230V electric panel.
We supplemented the default wall controller with a remote controller, so we can start/stop/adjust the heater from the aft cabin. It is wireless, a bit smaller than a car fob's, and it introduces the ability to schedule automated heating cycles (say, Mo-Fri, 5am to 6am). In the U.S. market, back in 2015, this was not available, even though it was offered in the European market. We bought it from HEATSO, the British company Eric of Kimberlite recommended. Note our remote is the _orange_backlit_version, which is compatible with the standard European _orange_backlit_bukhead_ controller. In the U.S., they were still giving away a 70's-style controller with rotary buttons.
After three years of winter use, the thing has proven 100% reliable.
The thing is too noisy, so we hate it.
Yet we love it and need it because we sail in winter and live aboard all year. We installed the Eberspächer silencer for the aft cabin duct because it was easy and cheap, but didn't install the silencers for the other two heating ducts, and most critically did not install the INTAKE silencer because hull #350 still has the short intake above the long cockpit locker. At some point in later hulls Amel put the intake at the bottom of the small port locker, so the Eberspächer intake silencer may be easy to install in these lucky cases. In our case, the intake sounds like we have a helicopter jet turbine about to take off from the cockpit.
Any Amels not having the forced air option preinstalled should install a quiet Hydronic heater. I know that's what I would do.
SM2K N°. 350 (2002)
En route, Porto Kayo to Koroni