[McGillicuddy]

It does ok considering its got three carbs.

It sucks gas at low speed so if you're planning on idling a lot or slow trolling get kicker motor.

I really like the smooth, even, seemingly effortless performance of the motor. The inherent balance of an inline 6 motor has a lot to do with that. But the right prop is the key to performance. My $50 13-3/4 x 15p Black Diamond aluminum prop bested 3 other props I tested in in top speed, economy, and grip but most clearly on the hole shot. Using some online calculators I'm getting about 7% slip (WOT)which I think is very good for an old design right out of the box. It gets out of the hole and on plane immediately. It cruises around 2.3-2.5 mpg measured by gps/navman inline fuel meter.

The sooner you get on plane the better with these hulls. The Etec has a huge advantage at low speed only burning what it needs. I've seen reports citing 26 mpg on a 20' hull (not a SeaCraft) @ 700rpm. Same for the Zuke 90 but keep in mind 7 or 8k will buy a lot of fuel.

Here are my results:
Quicksilver Black Diamond 13.75x15 Al
RPM SPEED MPG GPH
1000 4.10 1.80 2.28
1500 6.40 1.74 3.68
2000 7.30 1.50 4.87
3000 17.70 2.20 8.05
3500 21.00 2.30 9.13
4000 23.60 2.40 9.83
4250 26.50 2.45 10.82
4500 29.00 2.50 11.60
5000 31.00 2.40 12.92
5500 35.90 2.10 17.10

You'll notice a big gap where I just couldn't run at 2500 RPM. Just past 2K rpm it would bust up on plane and the motor would simultaneously rev up and haul out... I couldn't control its desire to get on plane.

Enjoy your new setup!