Plastic Fuel Tanks-Below Deck

[richie rich]

I'm in the midst of replacing my twin fuel tanks and was thinking about using a 60 gallon plastic tank to replace the 75 gallon aluminum tank in the aft section. I will still use aluminum for the forward 125 gallon. Does anyone have any experience with these newer poly tanks that are permanently installed below deck? Reason being, the aft tank barely gets used as I have never burned 125 gallons on any fishing trip in or around LI Sound. When I fill both tanks, the extra weight sits the ass end of the boat so low she never drains right, as this topic of discussion has hit the forum a lot lately. But thats another story.

Anyway, the tank gets filled sparingly, so with low or no fuel in the tank, the inside of the aluminum will protect itself and oxidize over time adding to future problems with crap in the gas when I do fill it up. I was hoping to eliminate these long term issues for a seldom used tank, plus save some weight to boot. But I have read that these tanks expand a lot, ie, a 40 inch tank will expand to 41+ just from normal swelling with the fuel, and they "bleed" a little vapor as well....no biggie I guess if installed right but I'd like to hear any pros or cons from anyone with experience or horror stories with these tanks. The price is also about 40% less than a quality aluminum version. Thanks

 

[CJBROWN]

My 'new' boat has a plastic/poly tank permanently installed. Does everything you mentioned, but no problems, and they never corrode through. The stock 208 is 82gal.

Leaving fuel in for an extended time is not suggestable with today's oxegenated gas. Definetely use a stabilizer, STABIL or AMSOIL, or it starts to go bad within a few weeks. You would want to rotate use, or at least use some and refill/refresh it, and treat it.

An extra 60 gal would add quite a bit of weight, with tank maybe and extra 400-450 pounds? If it came with a 75 aux back there I don't understand why it wouldn't be the same as designed originally. Isn't the boat setup for it?

 

[richie rich]

CJ, the original design did have a 75 gallon aluminum tank, but when you filled it, the weight of the fuel brought the scupper drains well below the waterline so your standing in water when bringing a fish in the corner of the boat and/or quickly washing down fish blood with the washdown. I didn't design it and it is what it is. So because I didn't use all the fuel in the main tank on my trips I stopped using it to avoid this problem. But from time to time I would and will use more fuel if I want to go on a long trip. The problem I see in using an aluminum tank sparingly is the slow and steady oxidation that will just get worse over time and will dirty up the fuel next time I fill it....and then get into the engines even after Racor filtration...its already happened before and I'm thinking the plastic tank would be better for this application.