Line for preventer?

[allene]

I can't comment on the line size you need but I can point out some things I observed on my boat, which has the same setup. First, any stretch and the boom can come around as it takes only about 10% change in length in the line from the prevent position to the boom straight back. You are right to use Amsteel as I tried using 7/16 StaSet and it has too much stretch, won't work. It would be OK if you only went from the boom tot he bow but the long run back to the cabin is just too much unless the line is very low stretch. What this also means is that the boom has huge leverage on the line. It just doesn't take that much force on the boom to really tighten up the line. Make sure you do these calculations before picking the line. I use I think 5/16 Amsteel line but just because that is what I had lying around. My boat is 36 feet. I don't think it is too large though.

Allen