Follow the suction hose that goes from the raw water pump (the weird brass pump awkwardly attached to the crankshaft pulley) to the hull. If there's a tee and a hose bib, you're in good shape; that's where you'll attach the garden hose to run the boat out of the water.
If there is no tee, then you'll have to improvise. There's a device called a "fake-a-lake", which is basically a toilet plunger with a hose bib on it - you brace it up against the bottom of the boat over the water intake, and turn on the hose. Never used one myself. Here's
a bunch of permanent mount solutions from Skidim. Alternatively, you can disconnect the suction hose on the raw water pump, attach a new hose and drop it in a bucket of water - the raw water pump will suck it up. Keep the bucket full.
I've seen a couple of fine-looking Home Depot-sourced solutions using a various brass bits. The Tee is easy; buy a cap to close the tee when you're not using it, and you're good. Make sure that the cap can't leak; it'll suck air through the cap and stop cooling the engine. You will have to have a way to shut off the suction hose down to the hull, however.