I went through the same when I was fixing a friend's 1990 Evinrude 70hp 3 cyl. Here's a thread on the subject and a solution for your engine, I think the Evinrude 70 pictured is the same as your model.
http://forums.iboats.com/forum/engin...a-cowling-seal
What I found on my 1990 70hp is that the seal not only is there to seal out water, but
most of all it is there protect the cowling from dings, like if you drop it or hit it against something (which I did after I had filled it in and painted it.!) That little automotive U trim the man used in the link above looks great but it does not protect against dings.
In the end, I concluded that it is better to go with the OEM seal, which you can get cheaper at nymarine
http://nymarine.ca/parts.htm or better yet, if you are lucky you'll find it on Ebay. Remember that if your same seal mold is used by a bigger engine, you can use it, you just have to cut it to your length, so you may find one on eBay that you can cut.
