I was constrained by the dimensions of the space I wanted to fit it into, but it's been adequate for me, even in some pretty cold temperatures... Of course, my boat is rather small compared to most...

A circulation pump is probably a good idea with a loop of that length, I was able to keep mine much shorter. My total loop only adds a few more feet from what I was already running through my hot water heater anyway, and I've never detected the slightest difference in my engine coolant temperatures...