Volvo RWD 200 Forum

You shouldn't have any trouble towing a boat+trailer of that weight, or even more. I tow even heavier boats, but always add a transmission cooler, use synthetic ATF (and engine oil), and have a Nissen 3-row (50% larger) radiator, all to deal with the possible effects of the additional heat to be expected (especially with summertime driving).

But sailboats (I have both a sail and a (heavier) power boat) may present a particular problem, depending on its design. You mentioned a "dinghy", and I'm assuming you'll have a retracting centerboard, etc. But unlike power boats which almost always have a planing hull (flat bottom), sailboats often have a deeper hull (round), which while facilitating stability when they heel (necessary in a sailboat) also require a taller trailer, and this means deeper immersion of the trailer, and farther descent of the car down the ramp, into the water to launch and recover.

So depending on the length of your trailer's tongue, and the slope (steepness) of the ramp (which is very variable from one ramp to another), you may have marginal "reach" for your wagon to launch your boat. Obviously, longer trailer tongues are better*, and so are steeper ramps. Be sure your tailpipe is positioned as high (close to the bumper) as possible -- I've encountered ramps where my tailpipe's mouth is dipping in the water and "gurgling" -- and don't shut your engine off at the bottom of the ramp if the tailpipe is dipping into the water!
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* Don't be tempted to reposition your boat farther back on the trailer -- this will unload the tongue and make the trailer unstable as it reduces tongue weight, whereas you want at least 5-10% (the more the better) of the total trailer's weight on the tongue!
If you find that you have a problem with tongue length, there are kits to extend its length, but are to be used only at the ramp, not on the road.
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The good news, viz your 245, is that it's generally great for this: the greater rear weight, together with RWD, means less slip on the slippery ramp (better than FWD, whose drive wheels are lifted when you pull up the trailer :-).

Have fun.