I broke two mainsheet blocks on my hobie 18 last summer on the outer banks. In one day of heavy seas I broke the lower block-Harken H170 which is standard for the 7:1 system. I had an old back-up block (Harken H170) which I later broke in the same seas. I obtained a Harken catalogue hoping to upgrade my mainsheet system but it seems the mainsheet blocks for both the hobie 18 and 20 are special orders from Hobie or from Harken. Looking on the internet I see that many H18 and H20 sailors do not use the standard issue hobie block systems. I would be extremely grateful if someone can provide me with thier recommedations on a new mainsheet system that would be rugged enough for the outer banks where I do most of my sailing.
FD

i used hangers (s hooks) on my 3 upper blocks when i had an H18 so i could easily remove them for breakdown and transit. this caused them to occasionally get tangled so i upgraded to a harken 57mm triple block.

I loved it and eventually upgraded to the 57mm ratchamatic base. I have now replaced the triple top for a quad and run an 8-1 on my mystere.

The 57mm is a good size for your boat (and most other beach cats). The new RonStan blocks (orbits) are nice too... and would work. the only issue i have is they use line instead of shackles and eventually may need to be replaced with new line... not a big deal but added maintenance.