Re: Where'd All The Gas Go???
It's mounted on the next to lowest setting (I believe it's the 2nd mounting hole). Unsure of the RPMs, no tachometer yet. Cruising speed is about 20 MPH according to our GPS so we're not beating this thing up. Engine runs very smooth, no strong smell of Gas. Could there be a problem with the Carb?
As HighTrim said, at wide open throttle, your gas consumption would be 11-12 gph. You are going at cruising speed which should be lower consumption because - theoretically - the engine's RPMs at cruising speed should be lower than WOT, burning less gas. My personal experience is that the "10% of HP" gas consumption at WOT is pretty accurate (give or take), and that my cruising GPH is about 25-30% less probably because my cruising RPM is about 25-30% less.
First question - are you really going significantly slower than WOT at what you consider cruising, like 65-75%? If you are going closer than that to WOT, like 80-90%, your consumption of close to 12 gph would not be all that surprising. It is also not surprising if you are pulling skiers, etc.
Second -Are you absolutely sure you're burning 6 gallons every 1/2 hour, not 4 1/2 or 5? Bottom line, your outboard will burn a lot of fuel no matter what you do. At cruise, I don't think you'd be doing much better than 8-10 gph (4-5 / 30 min). It could be that unless you're measuring your fuel consumption pretty carefully, it could actually be closer to 5 than 6 - therefore fairly normal.
Finally, without a tach, you don't really know if that cruising speed is in fact lower than the engine's recommended WOT. It is possible that your current prop and set up could actually run the engine at higher than recommended RPMs at wide open, therefore, the cruising RPMs, while being lower than that, are still as high as or closer than you think to WOT. Therefore, gas usage would be at the 11-12 gph rate. I have no idea if this is the case, but it is a possibility that only a tach will tell you.
So, to me, to know if you are really burning more gas than expected at cruise, you really need to know if you're cruising at less than the engine's recommended WOT. If it were my boat, I'd install a tach, or at least buy a "tiny tach" (available through many sources - Cabela's is one) to figure this out and also to fine tune your prop selection and engine set up.
As for engine set up, you probably know that performance (and economy) can be effected by the height and trim of the engine. You've mentioned the trim position - how about the height - the relationship of the antiventilation plate (aka AV plate, also called cavitation plate) to the bottom of the boat?
Are you absolutely sure the boat is not waterlogged at all?
