What determans a trailers weight limit. Can I make this work?

[Banage]

i found a trailer for my boat, but its rated at 600 lbs. As far as I can tell, my boat is 800 + motor. If i put bigger tires ( it has 4.8x8 i would go with 4.8x12 cause thats whats on the trailer it came from ) would that make up the difference, or do I need a new axle? http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_1063_1063 This is the one. What do you think

[Mr. Clean]

Your boat is 15' the trailer says it is for 12-14' boats. If you plan on using the boat I would at least get a trailer that would handle both capacities. Too bad you are not closer, I have a magic tilt that would be perfect (Florida).

[Banage]

thanks anyways. I got one today. its for a 15' only $150 bux. talk about a deal. It needs a paint job and miner TLC. Now i gotta find a motor. I got a lead on a 40 horse. I Excite!!!!!!