"Manual" . . . Don't get your hopes up. Boat manuals really don't exist, often just some basic stuff and safety information. Nothing detailed about the boat and its systems.
There is a thread or 2 here on iBoats about the same question (Renken manuals), but nothing found.
The engine is going to be the most documented, and from the engine manufacturer, not the boat manufacturer.
I also believe Renken went out of business in the late 1990's, so you are pretty much on your own to figure things out.
I don't even see that there is a Renken owner's forum, like many other brands. . . . However, many boats are built about the same way and use same/similar components, so you can gain knowledge from other sources, not needing to be Renken specific.
