Jumping in with Both Feet on a 20 Seafari

[Bushwacker]

Originally Posted by SailorChlud

Very interesting. My coffin has a 48 inch deck under it, not 60 inches. I wonder if having 12 inches of tank length unsupported would be a problem?

I have about 8 1/2 inch of depth to work with in the coffin, and a tank height of 7 3/4 is possible, because once the tank is under the lip of the lid, the under deck clearance rises to 9 1/4 inches.

The calculated capacity of OEM tank is about 35 gallons. I was able to put 36 gallons in it when filling to brim, probably due to additional volume in the fill and vent lines, but I put 34 gallons into I-Command system for fuel/range remaining calculations. If you install the quick connect fuel fitting on one of the output ports on filter to permit siphoning gas out thru the filter, you can find out how much fuel is unusable by dumping in 5 gallons, draining it out, and measuring how much you drain out.

I would just extend coffin deck with some 1/4" PVC or starboard. To maximize fuel capacity with the available space, one way would be to install a bladder tank, if you can find one with the right dimensions, although that may be a long shot. The other way would be to install 2 tanks that would each fit thru the hatch without having to tilt them, which would allow you to use more of the vertical space. (The OEM tank just barely fits thru the hatch, so Moesly designed it very carefully! I'd recommend modifying your mockup to those dimensions to verify fit before ordering one like it.) Before going the 2 tank route, I'd do some calculations to see how much of an increase you could get to see if the extra cost/work is worth it. On my Bahama trips with the old carbed gas guzzling 2S motor. I typically carried at least 24 gallons on deck in 6 gallon tanks and jugs, which was enough if we refueled at West End or Walkers. However after we couldn't get gas at Walkers one year, (fuel barge had not shown up and they didn't know when he was coming!) I started carrying about 80 gallons, which was enough to run all the way to Green Turtle. The E-Tec has proven to use about 50% less gas however, so fuel situation would be much better with current motor.

[SailorChlud]

At Denny's suggestion I modified my tank mock-up to the OEM dimensions Denny provided, and lo and behold, the mock-up fit first try.

So now, my theoretical tank capacity is up by 10% over my initial design. Might just make the difference between getting home, and not one day.

Here are a couple of shots of the modified tank mock-up. It is amazing how much cutting and measuring went into a basic trapezoid shape! Now we will have to see how much the extra surfaces and welds adds to the price compared to a rectangular shape.

[Bushwacker]

Originally Posted by SailorChlud

. . . I modified my tank mock-up to the OEM dimensions Denny provided, and lo and behold, the mock-up fit first try. . .

Yep, one good indicator of how well a boat was designed is how much thought was given to ease of maintenance! Moesly designed all those weird sloped surfaces on top and bottom of tank, so it would just barely slide through the hatch, and then he was smart enough to install it without using foam, which holds water against the tank, helping it to corrode faster!

Most boat builders don't even bother to install a hatch! They just drop the tank in, surround it with foam and cover it up with the deck. A gas tank inspection on them = checking bilge for gasoline!

[Dogbomb]

Denny hit the nail on the head.
This is the first boat I've had where the fuel tank was
accessible, easily removable and not buried in foam.
That's just smart engineering!
I hope your new tank slides right in.

[SailorChlud]

So far today we have had over 3 inches of rain, and rivers are rising, creeks, flooding, whitecaps forming on usually-placid bays. So what to do? Go pick up the boat after the dealer installed the new (to me) Johnson 115hp.

Here she is back home in the driveway. Now to get a fuel tank, harness, steering installed...and lights...and...and...

[Dogbomb]

She looks great with her new motor!
Sorry about all the rain. Hope things dry out ASAP!

[SailorChlud]

So the day dawned bright, cloudless, and 60 degrees for the high, so it is time for some painting and teak refinishing.

This is the teak after 2 hours of sanding, with the first coat of Cetol.