Motor mounting question???

I acquiered a tri hull via my mother-in-law. had it out Sunday on Bald Eagle. First thing I noticed was the big Evinrude seems to ride awful low in the water,and second sucks alot of gas
So would I get better performance and gas consumption if I raised the motor a notch or three? There is no power tilt and trim. And is their a good location to start with.

Thanks in advance

More info would be helpful.
Make
Length
Motor hp
And years mfgd
-Mark

Evinrude 115 horse. not sure of year early 80’s is my guess.boat length is 15ft. open bow. not sure length of shaft but I do know it is a long shaft moter. When in the water the discharge for water pump is well below the water surface I have never seen one like that. Are they not supposed to be above water line?

Thanks Mark when writing post last night I was having trouble wording the question. I had an alumacraft years ago and I moved the moter up 2 notches seemed to plane out much better. Please if you need more info Please everyone ask away I will do my best. I would like to get this resolved and fish this weekend.

Thank You

Paul

Unless you have a jackplate, a general rule of thumb on mounting a motor is to have the cavitation plate either even with or slightly above the bottom of the boat hull.
Now if your long shaft motor is mounted on a transom built for short shafts, you have a bigger problem that can best be remedied with the correct shaft length engine.

Herb has a good point. With the motor not having tilt n trim on it really hurts the gas mileage per hour consumption. Their is alot of drag on the motor when it is trimmed down all the way. As stated above, check to see if the cavitation plate on the motor is even or slighlty higher than the bottom of the hull.