Obtaining W/H time twards my 100T sailing as engineer

Good morning, I’m looking for a little guidence on a topic that I’m not entirely familiar with. I sail as a licensed Engineer with a NY based Oil moving company on one of their ATBs. I’d like to obtain my 100T W/H ticket and I’m curious about documenting my sea time. I’ve been with the company since 2012 working a two week hitch. On the captains watch only he and I are up, I function as a deckineer and often I’m in the W/H as lookout. I called the port captain and asked about a sea service letter to which he (without much elaboration) said get it from your Captain. So, I’d like to know the most affective way to approach a sea service letter in order for it to be applicable twards W/H time. Thanks.

You’ll have to log separate time. . So planning ahead, you can have separate days logged as a deckhand, or an os.(assuming you hold an OS on your mmd)…specifying you were part of a bridge watch and such.
Some engineer time can be used towards a deck license and visa versa though. I wanna say 90 days, I’m not positive. Refer to the 100 ton checklist.
For you to get a 100 grt master is possible, just have to make sure you have legitimate deck time worded in a letter correctly that doesn’t contradict previously documented engine time.

Thanks for the heads up; appreciate that.