Re: Silvertip respond please - and others
I do not have fuel consumption data on the Opti engines you mentioned and certainly don't have it on every boat those engines could be mounted on. The only way to prove or disprove your theory would be to actually install a fuel flow monitor or using Mercury's fuel meter and perform those tests. Theoretically (and give or take a bit depending on the hull), each of those engines at wide open throttle would burn 13.5, 15, and 17.5 gallons of fuel per hour respectively on exactly the same boat. While it is true that each engine has a sweet spot, each engine on the exact same boat would NOT be propped the same. The 135 would need a prop of lesser pitch than the 175 and the 150 would be close to either one in that regard. So the 135 would not have the top speed of the 175 and although it's speed would be less than the 175, it would in fact burn less fuel. Regarding the sweet spot, again, each of the three boats would likely have a sweet spot at roughly the same RPM, but the boat speeds for all three engines would be different. You can't change the laws of physics -- therefore if you want high end performance at a sacrifice of economy, go 175. If you want economy at the sacrifice of performance go 135. If you want the best of both worlds, the 150 may be the choice. The caviat I think you are after, is that a 150 running wide open (whatever speed that produces) may result in the same or slightly better fuel economy than a 175 running at its sweet spot. The converse of this is that the two engines running at their sweet spot will result in the 150 turning in the best economy at the cost of speed. And putting another twist on this, if "time" is crucial in your boating (as it would be for a tournament fisherman for exampe) you want to get from point "A" to point "B" as quickly as possible so your choice of engine would likely be the 175. If you ran the 135 it would take you longer to make the same trip so the difference in fuel consumption (because of the longer run time) would be of less importance than the lost fishing time. If time is not a factor, then overall economy is likely more important and the 135 would be the choice. All of this however assumes that the 135 doesn't end up being a "marginal" engine on the chosen boat. Overall however, I tend to agree that the 150 and 175 would likely perform very similarly with economy differing primarily by how either boat is operated and the conditions under which it is operated.
As for the 150/175 E-tec, they are the same weight (about 419#) and both are 2.6L (158 cubic inch) blocks. The reason you don't see a lot of E-tecs is quite simple. Brunswick (Mercury) owns about 40 Boat brand names. It stands to reason that they therefore package Mercury motors on most of those brands and the selling dealers may be required to order them that way. Some dealers simply don't want to or aren't qualified to handle Evinrude motors. BRP (Evinrude) is not in the boat business although they do have supply agreements with many boat manufacturers. Still, the manufactures offer all four engine manufacturers (Suzuki, Yamaha, Evinrude and Merc).
