Overall range of Seacraft 18

[Greno]

I have an 18 with a 175 looper. I have a 47 gallon tank with a usable amount of about 42 gallons that is based on pumping the tank empty through the bulb. I try to keep a full tank and have not yet run more than 25 miles in one day or more than 48 miles on a tank before filling it up. The fuel gauge is as accurate as most are and is off a little. I cruise at 28-29 at 4200 rpm with a 17 pitch prop. How is the range of 18's at cruise. Obviously my engine is an old gas guzzler, but what do folks with 2 strokes get? Is 2 mpg a good estimation for most folks?

[Ryank]

2 mpg seems to be the standard for most smaller boats 20-25 range. I compared til I was blue in the face my 225 Yami efi 2 stroke vs a new 225-250 4 stroke, and the MPG was almost identical. Might be better on a 18 or the tecs may be a bit better but 2mpg is good.
My 29 Whaler with 2 225 hondas was getting 1 mpg, thats why it needed a 400 gal tank.

[Greno]

we used to fish at 1 mpg on 1980s motors. It was very common for everyone to haul a drum on deck for a weekend of fishing. I still have a friend that has a 31 fountain and they typically haul at least one drum of fuel with them when fishing a tournament.

[eggsuckindog]

If you have the ability to figure your mileage just fill up before and after - should be close and 2 mpg is probably pretty close anyway, thats kinda what I use too.

Using my Flowscan, gps, fuel gauge and the basic fill up before and after, I am getting an average of 4mpg with a 150ETEC on my 20SF - cruises at 3800-4000 and 36-40 mph. I say this because I had a 175 carbed Yami - 1990 before I got the ETEC. Using the same methods, I got about 1.5 mpg with it on the same boat.

[Fr. Frank]

With a '92 carb'd Mercury XR4 150, actually dyno tested about 190hp, I used to average about 2.2 to 2.5 mpg on my 20' Seafari. My bet mpg was a trip from Marathon to Key West in Florida Bay, where the entire trip was on plane at optimum cruise speed of 27 mph, and I got a little better than 3 mpg (3.04).

I now have a lowly 90 hp Mercury Optimax on the back of my Seafari, and I average 5.1 mpg at 24 mph, and my best is 5.4 mpg on a run from Homasassa to Cedar Key and back.

Oh yeah, I have Pettit Trinidad bottom paint for extra drag.

[Ryank]

5.4 is awesome how does she move with some weight in her?

[Bushwacker]

Before I repowered I had a 1975 115 V-4 that I bought new when I bought my then 3-yr old Seafari. It used to burn about 8 gph at 4500 rpm/22-23 mph cruise. Over the 6 trips I made to the Abaco's with it, loaded very heavy, I averaged 2.8 mpg. I used to figure on 2 mpg just to be safe and have some reserve.

I just finished a 700 mile trip around Fla. with the E-Tec and averaged 4.35 mpg, again loaded very heavy and with Bimini top up but generally running in fairly flat water relative to the Bahama trips. I usually assume 3 mpg with it for planning purposes, but the neat thing about the E-Tec is that if you get in a situation where you're worried about running out of gas, just slow down to hull speed/900-1000 rpm! When they're running in the ultra-lean stratafied charge mode they burn even less gas than a 4-stroke! I have the I-Command gages with GPS spedo and fuel flow from computer, and it typically shows about 10 mpg at 5 mph! That system appears to be very accurate . . . every time I refueled the actual fuel used was within about 0.1 gallons of what the computer said I had used!

[Fr. Frank]

The 5.4 mpg was with the bimini top down, and just two people. Loaded with 6 adults, it planes in about 6-7 seconds, and has a WOT of only 30 mph, cruises at 22-23, but the rpms jump by 200 to hold that.

My prop is wrong pitch to run fully loaded. Max rpm with just me is 5200, max with 6 adults is only 4850. Recommended range is 5000 - 5750. My opinion on propping is that I should be able to turn Max of Max at Max for safety reasons. That means I should be able to turn the max 5750 of the maximum rpm range with the boat loaded at maximum weight. So with full fuel and 9 people in the boat, I want to be able to turn 5750 rpms at optimum trim.

I need a different prop, but haven't found the right one. I currently run a Trophy Plus SS 4-blade 13.25"Dx21"P. I need to drop that at least to an 18"P, but my local dealer hasn't got one, and since I've had this prop over a year, won't trade me for a new one, but offered me $250 in trade toward one ($650). I've had this prop over a year because he told me just to hang on to it and he'd trade when he got an 18" or 19" in stock.

[McGillicuddy]

Fr. Frank, That prop info is interesting. I'm surprised you can turn a 4 blade 21p SS wheel so close to target with a 90hp on the Seafari. I didn't even bother testing a 4b Trophy plus last year because it was a 17 or 19 pitch and I was barely reaching the target rpm on my 115 I-6 with a 15p black max...should have given it a whirl...might have to see if he's still got it.