Guesstimate My Range
 

I replaced my tank with a 40 gallon this year. I have a 79 V-20 with a 2000 150 Johnson. If you had to guess what would you say my range is at cruise?

My conservative guess is 34 usable gallons x 2.5 MPG. It is quite possible that your mpg will be better, but better safe than sorry.

Good
 

I replaced with a 40 gal as well and last weekend went 33.7 miles to J bouy, 33.7 back to dock and maybe 5 misc miles back to fuel dock. Thats a total of 72 and a half miles. It took 28 gallons to fill it back up and my DI Evenrude needs new plugs and injectors cleaned out. That would leave approx. 30 more miles to empty for a possible grand total of 102 miles on a 40 gallon tank @ 2.5 mpg

Hey Airslot, usable gallons is what? Because the first time I filled up the 40 gal from bone dry it only took 36 gal. Are tanks rated slightly lower than what they are ?

That is a VERY dangerous practice on that engine, always keep them in shape to avoid major problems. Plus your milage sounds really low for that engine, you should be able to get up around 4.5 MPG with a DFI outboard. As to the original question, I wouldn't try and push it past 75-80 miles on it. Your engine at a decent cruise of around 4000 RPM's will probably burn 12 GPH, and be pushing you close to 30 MPH(roughly 2.5 MPG). Now assuming any sort of reserve in the tank that leaves you the 34 gallons useable, which yields 85 miles of range.

Great info guys, I was thinking of making a run to the Old Grounds off of Cape May for deep water flounder fishing. It would be a total of 54 miles round trip. I figured at about 2.0 miles per gallon I would burn 27 gallons. I never really figured out what my exact fuel burn is at cruise so I was conservative at saying 2.0 miles to the gallon, I would hope its a little higher.

12 GPH at 4000 RPM's is a safe fuel burn number for that 150 JOHNNY-RUDE you have if your propped out right. 9-13 GPH seems to be the range that most see with them. The 175 seems to get the same fuel burn numbers as well at cruise, but only slightly higher at WOT. The 200/225's actually were pretty close to the 150/175's on fuel burn at cruise.

I estimated "useable gallons" because your pickup tube ain't gonna get those last 4-6 gallons out of the tank.

I would estimate 2 MPG on that 2000 Johnson. I have gotten anywhere from 1.9(rare) to 2.2(avg) MPG with my setup, so I base all my range off of 2 MPG to be safe.

-Svence