Hi Clay and welcome aboard! Congratulations on the 191 too. There is a great amount of information in our Triumph Boat forums compiled over 14 years that might be of help to you. The Boat Owner forums are available to Premium Member subscribers ($12/year via PayPal). If interested in subscribing click on the "Go Premium" button to the right of our logo above. That will take you to the info page on the subscriptions.
Regarding the rear deck cap, are you referring to the access hatch? If it hasn't been opened in awhile you may need to use a rubber mallet to assist in unscrewing it. You could always remove the screws and pry it off but be sure to user RULE Elastomeric sealant to reattach it or a replacement hatch. If you could attach a photo that might be helpful.
Again, welcome aboard.
Blessings
Randy
Admin
