Roy, thanks for input. And I'll apologize in advance to All for a long post.
On the Mercury outboards with only a 3 pound difference between 8hp and 15hp I too would definitely use the 15 instead of 8. What are the actual weights (or Model/serialNumbers--Mercury doesn't use Models, right?) of the 8 and 15 (with the 9hp being same weight as 15 in Mercury product line) ? It seems to me that the Mercury 8 is either quite heavy or the Mercury 15 is quite lightweight-- or maybe some of both.
I prefer Johnson/Evinrudes for 2 reasons (and admittedly maybe these are not really great reasons. Perhaps I need to "open my mind" a bit.). First reason is that I have been tinkering with OMC products for around 10 years, so that's where my hands-on experience (albeit limited) exists. Secondly, I have had trouble finding a knowledgeable and fairly-priced mechanic for small (< 40hp) outboards in our small town. I have found one good small outboard mechanic and he strongly prefers OMC's (and Yamahas). He claims that "Mercury's just blow up" and Suzuki's self-destruct via corrosion. Although I have friends with larger (>40hp) Mercurys) and their experiences have been no worse than my experience with my 90HP 2000 Johnson, I am inclined to stay with OMC's based on my mechanic's advice.
So...here are the weights that I know for OMC's. I have a 1969 6hp Model 6R69 Johnson (runs great!) listed Weight on iboats website is 51# (I weighed it at 54# --so there is a 3 lbs discrepancy). I am considering purchase of a 1985 Evinrude 8RCO which iboats lists as 56# (and Sellers have weighed at 56 to 58#). I am also considering purchase of a 1986 9.9 Johnson 10RCD which iboats lists as 72#. iboats also lists 1986 15HP Johnson 15RC as 72#. So in the Johnson/Evinrude product line there is a 16# difference between 8HP and 9.9/15hp. This makes sense as I understand only difference 9.9 vs. 15 is carburetor.
That 16# difference seems significant when I am hanging it on my Higbee's transom, or lifting it with my aging lower back (I spent a year or so getting chiropractor fix on my back not long ago).
A couple years ago I bought a really sweet used Mercury 6hp (s/n was either 3372456 or J3061988--my records are unclear). It weighed a whopping 70 lbs! This is compared to 54# on my 1969 Johnson 6hp 6R69M. But if a Mercury 9.9 or 15hp weighed only 73lbs (=70 +3) then that would be comparable to OMC weights.
I will do some more searching on websites for Mercury 9.9/15 weights--maybe I am missing some good deals on a used Merc.
Dave my 8hp merc is a 1999 sticker weight of 73 lbs. My 15hp merc is 2004 and sticker weight of 76 lbs. Both short shaft tiller motors. 9 hp in 2004 model year should be same weight as 15 hp. I do know the 8 can,t be bumped to 15 by changing carbs, etc. but the 9 in 2004 could be.
Thanks again for all inputs.