I run an '83 blue band Merc 115 on a 20' Seafari. I'm not sure what blue/red signifies maybe salt vs fresh or 20 vs 25" shaft?
At any rate I get best performance with a 15p Black Max prop.
36mph@5500 rpm 2 mpg.
Best economy comes @3750-4200 rpm getting 2.5 mpg at 23 to 27 mph. Fine motor but I'd swap it for a dfi 2S or that Zuke in a heartbeat if I had the extra $8K.
It would easily double my range and likely come close to tripling it. That is huge on tuna excursions.
Etec 90 is about 325 lbs and probably gets better economy than the Zuke throughout the rpm band... I understand the desire for a 4 stroke and that Zuke is the best of the lot, but check out that etec 90... and compare boat performance tests... I think you'll be surprised by what you find...
