I ran a mixture of 300 & 500W halogens on my first rig, hooked to a Champion 3500W genny.
The general rule of thumb is to keep your running watts to around 80% of the rated running watts of the generator.
Since I built my new boat, I've switched over to running HPS lights. I've got 8, 150W HPS on there & I get roughly 5 times the lumen output of Halogens, for 1/3 the watt consumption. I also have amps to spare by hooking up to the 20A RV socket of the generator. I still have enough power to run my 750W IOTA inverter to power the trolling motor, which increases my fishing time & lets me get away with not having to constantly charge batteries.
The initial expense can be a little daunting (around $70 per fixture, compared to $5 for halos) but the benefits far outweigh the cost.
Here she is in daylight.....
And a night-shot.....
Incedentaly, the $12 Walmart ropelights around the interior gunwales are THE best addition I've made! I have them switched separately from the fishing lights to make driving on the big motor easier, but for unhooking fish, de-tangling line & finding the beer I just dropped, they're amazing.