I have a Harken furler for the headsail on our boat. It is a Mark II, probably from the late 1980s. From a search on their website, I understand that Harken is currently selling Mark IV models. Can anyone tell me what the difference is between a Mark II and a Mark IV? I am less interested in cosmetic changes, but rather anything that substantially affects it's efficiency, safety and general operation.
Thanks,
Frank.

New bearings (Torlon) so smoother operation, better halyard swivel, dual tracks, removable drum (if you care about racing). Oh yeah - and it comes with a crappy furler line (very slippery) so expect to replace it. We went from a Mark I to the Mark IV. It's definitely a lot easier to manage under load, but that could have been due to the upkeep of our prior furler (which was replaced due to the torque tube splitting). In general, we like it. By the way, it uses new foils so you will have to replace your current ones, meaning you will also probably have to replace your headstay.

I'll second that!!! The stuff is like water ski tow rope! You'd think that for a $1600.00 furler they could at the least throw in a line that costs more than .02 per foot!!!

Same here! Unbelievable, actually, that they do that. We're finding it tough to use, and will likely replace it soon.

We're definitely replacing ours this season. I'm guessing the reason they went with it was to reduce the friction in the drum, allowing the line to stay nice and taut inside as it furls. Whatever the reason, it just sucks.

I'll be very interested to hear what you decide to replace with and how you like it...thanks in advance

Having owned a Furlex 200S, on a past boat, I have to say that line is some of the best I've ever seen. I love to replace my Harken line with it but I just don't know where you can buy it commercially? It's a white line with black tracers.. Any ideas on where to get the line that comes standard with a Furlex?

We replaced our line on our Mark I furler last year due to diesel being spilled on it. The replacement was actually fairly nice. I'll see if I can figure out what it was. It's a turquoise blue with white flecks and I believe about 3/8". I think it's in my basement, but I'll be putting it back on in the Spring and taking that crappy black polypropylene-like line off... According to the docs it's "8mm single braid polyester" but it should just say crap .