Jumping in with Both Feet on a 20 Seafari - Page 7

SailorChlud · #61 03-09-2017, 06:46 PM

Here is the tank mockup getting installed. Based on this, my width can be 1/4 inch wider comfortably, but needs to be 7 - 3/4 inches high instead of 8 inches to accommodate the height of the vent fitting.

SailorChlud · #62 03-09-2017, 06:49 PM

Here is a shot of the clearance of the tank fill under the deck. Looks good.

SailorChlud · #63 03-09-2017, 06:50 PM

whoops - cannot figure why it came out upside down?

Bushwacker · #64 03-10-2017, 01:03 AM

John,

I have the dimensions of my OEM tank somewhere, so I'll try to dig them up and post them on here. It's square on both ends, but the bottom slopes up at the front, and the top slopes down at the back. All that is done so you can get it in and out of the hatch opening. It holds about 35 gal. and has the vent fitting at the front, port side, with pick up and fill fittings at the back. Denny

SailorChlud · #65 03-10-2017, 01:50 PM

Thanks, Denny.

Bushwacker · #66 03-13-2017, 10:07 PM

Finally found measurements I had made when I pulled fuel tank to inspect it during repower in 2006.

The tank coffin is 25" wide, hatch opening is 22.5" wide x 37 3/8 long, tank is 22" wide and 60" long, as shown in sketch below. The fill fitting is angled back at about a 30 degree angle, so it's sort of pointed at the fuel fill on gunnel.With the tank all the way forward in the compartment, the aft surface of tank is about 3.75" forward of the bait well under port stern seat. The hatch overlaps the front edge of tank by 2.5", so I suppose you could make the tank about 1-1.25" longer if you reduced distance between tank and bait well and continued the sloped aft top surface at the same angle. If you really wanted to get maximum capacity in the existing volume, you could make 2 separate tanks, which would allow you to make the tanks a little taller, plus you could eliminate the sloped surfaces, since it would be easier to install a couple of 30" long tanks than a single 60" long tank! Of course you'd also have to run separate fill and vent lines, maybe out the port side.

John, I suggest you modify your mock-up to these dimensions and test fit it before you order a tank! Denny

SailorChlud · #67 03-14-2017, 06:21 PM

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.

SailorChlud · #68 03-14-2017, 07:05 PM

Using the 48 inch length I made my mock-up, I calculated the total theoretical capacity at 33 gallons, but I would like to get a few more gallons in capacity if possible.

Bushwacker · #69 03-15-2017, 04:14 PM

Quote:

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 · #70 03-26-2017, 04:10 PM

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.