We have a 97 marlin. We just repowered with 2018 300 4 stroke Suzuki's.
We have put 22 hours on it on Labor Day weekend. The first 10 hrs being the initial break in.
On Monday we did a trip to the canyons off of Cape May. Trip was 70 miles out. 70 miles back and 7 hours of trolling.
With our ox66's we would have burned about 210 gallons. We would have cruised at 24 knts out and about 26 knts on the way back being half empty.
With the new motors we burnt 152 gallons, cruised out at 29 knts at 4200 rpm and cruised back at 30.5 knts at 4200 rpms.
As far as weight, Suzuki I believe list their weight full of oil and props. Yamaha list their weight dry with no props.
So by the time you take out the oil tanks it is only about 100 lbs more.
We did not notice any difference and our scuppers are above water.