Arduboat on a retired board

Ok, I know there will be some looking down and suggestions to upgrade, but…
I have this APM2.5 board laying around and doing nothing. I also have a GPS, Telemetry, and power module. Here is the thing: is it possible to get an arduboat installed on it? How hard would it be to separate the boat code from everything not related and flash it on APM? It feels to me these older boards can have a second life if used for some less demanding applications.

You can load Rover 2.5 or earlier on it . I think 2.5 was the last APM 2.5 useable code. Check the Docs.

It’s 2.5 beta1 actually, I know. It does not contain boat code though.

I used a APM 2.5 on my boat years ago. The rover code work well for what we had back then. Rover 2.5 will work just fine on a boat. You just don’t have a more refined code. Missions work.

I would prefer the newer code as the old one does not do many things. Also, looking for documentation for old software is a bit hard.

Get tyourself a Pixhawk 1. mRo is a good source for something that will work for you very well.

Please read the initial question.
I have a few Pix boards, they are in use. APM is laying around and doing nothing.