Osprey 170 increased capacity fuel tank idea

[powersportcomposites]

So its time to rip the tank out. My boat smells like gas, especially under the console. I want to check it out. I know she is most likely due for a tank.
As this is going to be my reef boat and soon dive boat, I had an idea yesterday.
But I need info or pics from somebody who has really chopped into one of these hulls.
As we all know there is a "coffin" that the tank fits in, and because of that, it would be hard to fit a larger tank without installing a larger tank. But....what is under this coffin? Would it be possible to drop the floor in it down another 6 inches, essentially doubling the available fuel tank space available?
Thanks

[Blue Agave]

Removing the sub-floor the tank currently rests on will give minimal to no additional room for a larger tank. One option would be to cut out the front wall of the coffin box, this would allow you to slide in a longer fuel tank.

[Fletch170]

worked at a gas dock when I was 17, watched a woman pump 60 gallons of fuel into a rod holder....... that was a funny day.

[powersportcomposites]

haha O boy.
I was thinking as an alternative, just use regular size tank, and then I could bring my 12gallon removable above deck tank on those long haul trips......?

[Blue Agave]

haha O boy.
I was thinking as an alternative, just use regular size tank, and then I could bring my 12gallon removable above deck tank on those long haul trips......?

That would certainly work. Another option would be a Bladder tank which can be rolled and put away after use.

[RickK]

Couple questions and I apologize if you mentioned this earlier:
1) What year is the boat?
2) What size motor?
3) Most 170 tanks are 27gal - at mid-range you can expect the boat to burn around 6 gals/hr avg at about 30mph.  That's a long way on 27 gals.
4) How far are you going to go out in a 17ftr? 20 miles? Probably not a great idea unless you have a buddy boat and then it's still iffy IMO.

[powersportcomposites]

Great questions rick!
Boat is a 1981 Osprey 170 with a 100hp johnson javelin. At the moment the motor averages 2.3 mpg. I have the boat on a lift 13 miles from Sanibel. Therefore, that is 26 miles before I even leave the sight of land. I like to go by the rule of thumb that you should have twice as much gas to get home as it takes to get to the destination. So let's just say hypothetically the 26 miles coming into and out of the river account for 11.3 gallons going offshore. Which gives me a range of 5 ish miles if I stick to my "twice as much gas to get home just in case" theory. Alternatively I could gas up after getting to Sanibel, but I prefer not to pay marina gas prices if at all possible.

[RickK]

PSC - you kinda lost me there.  Are you 13 miles via water from Sanibel or 26  I thought you were using a round trip mileage but seems maybe you're not.

[powersportcomposites]

26 is round tripileage to get to the point where I start going offshore. Sorry it was confusing.  I'm 13 miles up river basically

[wingtime]

I seem to remember a member on here replacing a 170 tank with a larger tank that fit in the coffin...  I want to say he was able to get about 35 gallons.  The coffin looks like a bath tub inside.  You would have to have a new tank made anyways so it wouldn't cost you much more to have one made that takes advantage of the unused space in the coffin.  Of course the other option would be to re-power with a more fuel efficient motor.  Say a 90 hp Etec.   Also a Flo-scan fuel flow meter will help you save and accurately manage your fuel.   The Flow-scan will allow you to better use the 1/3 fuel rule. 1/3 of a tank to get you where you want to go.  1/3 to get you home and 1/3 for a reserve.

[powersportcomposites]

I definitely plan to repower, when funds allow

[Blue Agave]

better use the 1/3 fuel rule. 1/3 of a tank to get you where you want to go.  1/3 to get you home and 1/3 for a reserve.

Bingo!