Originally Posted by boatster_sr4
For me I'd look at the fuel economy between a 90 and 70. I've got a 70 hp Johnson 2stroke and its plenty of power but I don't tow sailboats. A 90 would be nice if I could get the same fuel economy plus the extra power when its needed. Otherwise most of the time I'm trying to run at the most fuel economical range. For me its mostly about fuel economy short of buying a 4 stroke for now
Hence the choice of the direct injected E-TEC two stroke, which is as clean and economical as a 4 stroke (some would argue more so), at a substantial weight savings.
ANY new tech motor (DI 2 or 4 stroke) is going to be one hell of a lot more economical than your old 70 or my old 80 carburated guzzlers! Most reports I've read indicate increased cruising range of 50% - 70% on a this sort of repower to the E-TEC. I've heard 90 & 150 E-TECs at idle and cruising speed, they're also amazingly quiet in comparison to our old motors, very similar to 4 strokes.
Most of my use is idling around, following sailboats upwind, then high displacement or low planing speed following them downwind, with occasional relatively brief high speed blasts, setting race marks and such. I'd go through 7-10 gallons/day doing this with the old Merc. I expect to see that drop to 3-5 gallons/day.
I want the power to be able to tow a heavy keelboat (Sonar or J/24, ~2500-3000 lb) at planing speed, or in case of a need for high speed emergency response. I've also had to do high speed mid-distance runs for spare parts, where speed is hugely important
The E-TEC 75 and 90 are the same motor, but for a different ECU and intake, as far as I've been able to discern. Other than at WOT, the should be equally economical.