Check out
http://media.channelblade.com/boat_graphics/electronic_brochure/Company624/_17_427200741404PM.pdf for more info.
I have an '86 mariner with 450 hours on it. I love the boat with a few exceptions. To get the amount of room and space into this boat, they squished the bottom to a weak 10 degrees so the ride can be quite rough in a heavy chop. Check the weep holes under the cabin sole (7 I think) and in the engine compartment (9 i think). Unfortunately they did not seal these up and they are prone to water damage should a previous owner let too much water get in the bilge.
I take the boat to a plane and keep it right there. Depending on sea conditions, trim, and load. That is roughly 28-32k rpm's and I averaged over the summer 1mpg. Not bad for a tank like this. My transmissions are similar to yours but the gearing was changed slightly after 1986 (I think to your benefit). If you have to work on or pull the transmissions be prepared to have a little less skin on your knuckles!
I personally prefer the voyager design because of the lower helm, but would not pass up a mariner platform as I only wished I had a lower helm once this summer. Honestly, don't think I would be comfortable driving from the lower helm.
If I had the money, I would sell mine and buy a 92-93 28/300 sedan as I like the layout better but I am broke so I stick with the Mariner.
Hopefully not being too negative, just trying to express my opinion. One more quirk is that the dogs can't get into the v-berth without lifting them in.
Hope that helps. If you are interested in a 1986 in excellent condition (Interior looks like It was installed in '86 and never used) I would let it go for $22,500 which is what I paid for it plus the cost of the improvements I have made to it. I'm on Lake Erie.
Thanks,
Jim