Re: For Frank Acampora!(mostly) anyone please chime in too
First you need a transom to hold more motor, if your is the same as my '83 I'd say some knees and thicker transom are needed as its only 3/4. I thought about doing that and running a jack with the 85hp.
According to some stuff I look up the 85hp is prop rated after '83, some say no. So, I dug up my manual and it only says BIA rated@ 5000RPM, 72.39CI, 275lbs with trim/tilt.
You could run an inline Merc, they are under 300lb and 115HP, you can even cheat and put a 90hp cowl around it. Most other motors are heavy, in particular newer ones, and that changes handling and speed in a negative way. Naturally the older motors are not going to get better mpg no matter the brand. If I bought one today it would be an etec, just my choice and it might depend on what I found a deal on. I think but not sure you could put a 4cyl power head on the 85hp leg I think it is the same but check first.
Really other things are best for performance, like taking any extra weight out of the boat, having the prop done to performance specs, rounding the front of the skeg/LU some, ensuring the pad/bottom is straight and smooth, putting the weight more to the stern of the boat, raising the motor some, all that stuff. I get 43gps out of my 16 capri, sometimes only 41 and change with normal LU lube and different weather. But I could repeat 43 with synthetic lube and most weather with a thinned and cupped SS 19p just me in boat. Gets on plane better with the trim up, fairly fast, it runs pretty good considering. I'd like to see 50mph, but hey its not that kind of boat like say a hydrostream, and really for a 16 bowrider that speed is respectable. Most of these the foam is full of water, increasing weight and slowing them down.
Another issue is its hard to fit a performance prop to these.