The boom is definitely 170, I put it side-by-side with the boom from our old (170) boat and they are identical. The mast is not identical, I have noticed the following differences:
- The main sheet luff has no plastic slugs, the luff rope slides up in the mast slot. The slot is considerably smaller. The boat came with a sail that has the 170 logo on it and the plastic lugs were clearly cut off to make it work in this mast.
- The step attachment is completely different, you have to position the mast on the step, insert and secure a pin, then pivot the mast up. Not nearly as simple and easy as the 170.
- There are 2 internal ropes in the mast, one for the main sheet and the other (I think) for the optional spinnaker. On the 170 all the ropes are external. The mast has no attachment point for a topping lift. Could use the spinnaker line but it comes out the front of the mast, not ideal.
- Standing rigging is an open question. The Hunter 18 specs indicate 52" tip-to-tip on the spreaders, but this boat clearly has 170 spreaders that are several inches shorter (compared to our 170, identical). We bought some H18 spreaders but they don't work because at 52" spread the upper stays are too short to allow the mast to stand fully upright even adjusted to the highest pin in the chainplate. We can either (1) get longer chainplate for larger adjustment rage, (2) use the 170 spreaders, or (3) cut the H18 spreaders to the 170 size. I think all the standing rigging is a bit off, but the owners manual has no clue on how it should be adjusted (mast rake, amount of slack in the stays, etc).
My theory: Original boat was a 170 (which is what the hull ID indicates). It suffered from major cracking and at some point they got Hunter to swap out the 170 hull for a new H18 hull. Most of the rigging and sails were moved over. The mast is probably H18 because the mast step differences did not allow that reuse. Everything else was adapted - the main sheet lugs were removed, standing rigging adapted, etc. Original specs for the H18 was a larger main sail, but I understand that currently the 170 and 18 main sails sold by Hunter are identical in size, just a different logo. This is Hunter's (now Marlow-Hunter) attempt to make the 170/18 sails interchangeable so mash-up boats like this will work with either one.
We have ordered a new main sail from here at sailboatowners.com.
The adventure continues...