Hello Stephen
Firstly, your inboard should provide more than enough oomph to push your Atalanta along – even against an ebb tide. You might consider checking your motor setup. If this is for A89, as I recall she was originally based on a lake and had a hydraulic drive – and is still the case, you may consider switching to a direct drive to add about 25% more power.
On the outboard options, many Atalantas have had outboard motor installations – including my current one (A169) when I originally acquired her in 2011. The outboard had a complete wired setup with ignition and morse controls routed to cockpit. I removed the installation as part of a total refit/rebuild – there are some archive photos of her with this setup in one of the back issues of the Annual Bulletin (also other Atalanta outboard setups as well. I have now a Lynch 48V 7.5 kW electric inboard motor. For any extended motoring I also carry an old (refurbed) Seagull SP 5hp outboard motor with a Seagull removable outboard bracket – from Sheridan Marine – with a long range tank. Some early Atalantas used the same long-shaft big prop Seagull engine instead of an inboard; one interesting article is in an early bulletin issue has the motor mounted on an outboard bracket outside the cockpit.
This link shows my transom outboard bracket holder installation i.e. for the seagull bracket bolted through to an internal 20mm hardwood backing plate
https://drive.google.com/file/d/1jISSTqvX3o8P04Vs3yTGdfE-5-7jaCce/view?usp=drivesdk
I hope all this is of some help.
Chris