I got a 14' Aluminum boat I am making a small casting deck on the front. I have a piece of marine plywood and I am in the process of putting 3 coats of spar varnish to seal the plywood. What adhesive should I use over the spar varnish to ensure it sticks to the rubber backed marine carpet?

 

I called Roberts about their 6700 adhesive and they told me it wouldn't adhere to the spar varnish. I then called DAP about their Weldwood Outdoor Carpet Adhesive and they told me the same. But from what I have read, it seems like people used these exact adhesives in the exact scenario and haven't had issues.

 

I was also thinking of just using a staple gun to get the carpet in place. Any thoughts on that?

http://www.iboats.com/Boat-Carpet-Adhesive-Gallon-Advance-Adhesive-Technologies/dm/view_id.686895?mkwid=ZOo40XWI&crid=12352303392&mp_kw=&mp_mt=be&pdv=c&cm_mmc=Microsoft-_-Mall+New+Shopping%3ABing-_-All+Products%3AMall+New+Shopping-_-KWs+Sitelinks+PLAs&utm_source=bing&utm_medium=cpc&utm_campaign=Mall New Shopping%3ABing&utm_term=1100101400095&utm_content=All Products%3AMall New Shopping

Have you used that adhesive? It doesn't very well reviews and this is the first I've came across it. 

 

Has anyone used the Roberts 6700 or Weldwood outdoor carpet adhesive over the varnish? I have read that others have.. and they say it has held up but the manufacturer doesn't say I should do it.

I made a small platform out of birch that i sealed with spar varnish and used outdoor carpeting adhesive that i bought from Menards or home depot  Been on the boat 4 years now with no peeling

This stuff?

 

https://www.menards.com/main/flooring-rugs/carpet-carpet-tiles/carpet-installation-maintenance/tec-reg-indoor-outdoor-carpet-adhesive-1-gal/p-1450446645591-c-6538.htm?tid=-2931656997483751216 

That might be it

I would use Loctite construction adhesive in a tube from Depot/Lowes/Menards.