18' Superfisherman performance

[Fr. Frank]

I've finally put the 18' in the water. It has a 1987 Mariner 115 hp motor, with under 200 original hours. I put a 4 blade Turning Point aluminum prop on it, 17" pitch.

The 1987 115 inline 6 cylinder is the same motor as the old 140's, right down to the size of the jets in the carburetors. We tried to put it on the hydro-dynamometer, but had to look at the gauges, as the computer interface wasn't working, and the printer was out of paper. It appeared to be producing about 123-125 hp at the prop-shaft.

Auto-Blend oil mixing is disabled and removed, running on 5-:1 premixed fuel. There are no trim tabs, but I will be adding Sport Tabs later because Choctawhatchee Bay is frequently very choppy.

Hole shot is very impressive, at just over three seconds. Very little bow rise with the stern-lifting 4 blade prop.

Best cruise seems to be at 3700-3800 rpm and 25-27 mph.
Top end is at 5800 rpms at about 41-42 mph.

Overall, I burned about 8 gallons in just over 80 minutes and traveled 31 miles according to my GPS, with an average speed of 17.8 mph over the entire time, for an average of almost 3 mpg. That actually surprised me, as I was expecting a fuel burn closer to 2.3 mpg based upon owning many inline 6 Mercs over the past 40+ years.

I'm looking at/considering repowering with a new or NOS motor in the 90-150 hp range. So far, I'm leaning toward either a Suzuki 115/140, or a Mercury 4S 115EXLPT Command Thrust or 150EXLPT, both of which can be found as NOS leftovers in the 2015-2016 model years, with a purchase price of $7600 to $8100 for the Zukes to $8300 to $8500 for the Mercurys, not including rigging, controls, gauges, or props.

I leaning toward these motors mostly because of price, because the Etecs are 2017-2018 model year only for an extra $3K, and because Yamaha now wants you to replace the flywheel/balancer assembly on 2014 and newer motors inline 4 and V6 motors every 80-100 hours because of known failure issues, and it costs over $900 each time.

If anyone has simple data on the Zukes and Mercs, let me know. I can't buy the motor until July, though, as I'm taking a sabbatical trip to Israel in June, and have to pay for that first!