Engine

Time to start thinking about this engine thing. It's a Stuart Turner, and I think, from looking around the web, that it is a P55M model. I can't be sure though, as the plate which should be there no longer is. Here are some pics. Can anybody confirm it for me? It starts with a hand crank - no starter motor from what I can tell. The magneto is labelled "Lucas".

The engine has a forward and reverse gear, and a little knob to control revs.

Luckily, the thing isn't seized, I can turn it quite easily, and the moving bits look well lubricated and free from rust.
My knowledge of petrol engines is remedial at best. I don't know the process for starting it, as the knobs are all unlabelled. There is also a dipstick, which surprised me, as I thought petrol engines had the oil mixed in with the fuel. Maybe that's just outboards. The oil on the stick looks pretty clean but I'll drain it anyway, once I find the plug (any suggestions where that might be? And where do I pour in the new stuff?).

I want to begin by cleaning it up a bit, replacing the oil and fuel, and giving it a new spark plug. I daresay the water intake pipes might need looking at too - the valves look all rusted up. If I'm lucky, that might be enough to get something happening.

Where the handcrank shaft meets the magneto, it rattles around a bit. Any info on how to tighten that up? You can see where it enters in the fourth picture below.