What part are people using for the exhaust port in rear of machine? I have seen links to a part on Amazon but I can not find it now 
TIA
This one has been mentioned in posts on this forum http://www.ebay.ca/itm/Brand-New-4-In-Line-Marine-Bilge-Air-Blower-DC-12V-6Amp-270-CFM-Quiet-for-Boat-/121861740679?hash=item1c5f869887:g:zVMAAOSwEetV9xqs&vxp=mtr
Search “exhaust” and “marine” in the community search field on the left to see member’s posts.
@Ulf_Stahmer Thanks, but I am looking for the part that attaches onto the back of the machine in the slots like the stock POS fan does. Not the actual fan itself 
None, I just removed the exhaust port & put the fan back where it was. Probably not ideal, but I will sort something better when I get around to it.
Oh, I remember seeing something someone posted about buying a flange at HomeDepot. I made my own for a few dollars out of a 3-1/4" x 10" duct takeoff and some spare plywood. I posted the photos here. Search on “exhaust” to see them.
I bought this. Was cheap and said to fit perfectly.
Yes. That’s the one I saw posted. Hope it works for you!
I bought the 4" bilge blower, ~250cfm and a 4" flex hose. Pinched that directly into the opening on the rear and liberal use of the aluminum (real) duct tape.
It is advisable to put the blower nearest the outer end of your exhaust, this creates a negative pressure along the entire run, helping to prevent fume leaks.
@Greg_Curtis_pSyONiDe I bought a 6". It was cheaper than most 4" ones so I am going to use a 6"-4" reducer. Yes, I was going to put the fan on the end of the tube opposite of the exhaust port of the machine.
http://www.ebay.com/itm/172203049670?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I used a floor register vent something like this: http://www.lowes.com/pd_36418-85334-GVL0084___?productId=3134369&pl=1&Ntt=floor+register+box
There are lots of choices of these types.