wow!! my girlfriend bought me a boat! Could use some advice though.

[banjosareunderrated]

it's an 86 galaxie granada. 17' long, 7' beam with a 170hp Mercruiser in/out. I've never had a powerboat before, but the engine looks just like a 4 banger to me. It's a 4 cylinder with plugs, wires, cap, etc.

I took it out 3 times last weekend. The first two times, it ran great: the speedo doesn't work but it felt like it got up to 30-35mph. The 3rd time though, i got a TON of white smoke from the engine. It was anti-freeze. The radiator boiled over, but not the overflow bottle. My first thought was a bad thermostat but now that I think about it, i'm wondering if maybe the impeller got choked with weeds. It was a mile or so trip back to the dock and by the time i got back, there was no more smoke and my temp dropped back to 175. Since then, I used an earmuff with a garden hose and up to 3500rpm and no more coolant boiling.

Any thoughts? Is it common to choke an in/out with weeds?

any help is appreciated. have a great weekend!