Ah yeah, that would be the setting for your Home Page which you can setup in the General tab of the Shop settings I believe. You'll see towards the bottom it asks you how you want your Home Page displayed and if you want to link it to an outside page and such. That's where you'd put the URL for the page you want the Home button to go to if you don't want it to be your shop home page.
I am thinking the link
www.havelock.net is incorrect as it sent me instead to
http://www.firstcarolina.com/ which has nothing to do with boats hehe.
As for the reason I suggest you get a domain name for the boat site, is because even though it's a subdomain setup of your havelock site, that site really isn't about boat parts, it's not really connected other than to be your site and maybe location wise in the area. You should always have a domain name for specific sites when you're doing a business to make it easier for people to find you and easier for you to list it places to get more traffic on it. Just a suggestion of course, but they are pretty cheap and it would be worth the cost for it in the end.