glassing a steel deisel tank?

[jfc6570]

just purchased a 1977 36 pacemaker , converted to deisel 3 years prior , when purchased old owner thought rear tanks leaked, becuase bilge had deisel in it . have not preasure tested yet , but tanks look very good outside with no visable leaks , my questoin is for peice of mind can i remove the tanks and incase them two or three layers of glass ? i have done many projects with boats and glass , and also ask friends in the buisness , and every one just kinda scratches thier head with no difinative answer.

thanks
jim

[marshmat]

I'd advise against glassing the tanks. The fibreglass will tend to trap water against the steel, creating near-perfect conditions for rust to spread like wildfire.
If you take the tanks out, you can inspect them pretty thoroughly. Small leaks might be repairable but if there's significant rust, they deserve replacement.

[jfc6570]

i thought of that too , with the aspect of condinsation , my concern with a patch is popping off , my cousin retired chief bosun c.c. said they weild steel diesel tanks all the time , and for rust i detected none , and the inside
" should " not have any because diesel is a lubricant , maybe a preasurization will tell me more ?

[Toot]

You don't have to just slap a patch on the outside of the tank. You can drill or cut a hole, cut a patch to match, tack weld it into position, and then go all the way around. When done, it'll be pretty much as good as new and should be fairly flush.

Fiberglass seems like a losing proposition in this case. And, heck, I'd bet welding would be cheaper. You could probably get it done for maybe $50 as a carry-in/carry-out job at a local auto restoration shop.

Do a pressure test. A gas cap, a bicycle pump, tire gauge, a tap, a valve stem, and some teflon tape is all you really need.

It could just something dumb like a leaky cap allowing vapor to escape and condense on a surface outside the tank before dripping down into the bilge water.

[marshmat]

No rust on the outside? The diesel in the bilge is probably from a bad cap or fitting somewhere then. The pressure test will help confirm the tank's condition. As Toot says, it's not hard to repair steel.

[buckknekkid]

Weld the sucker !

[Toot]

Originally Posted by buckknekkid

Weld the sucker !

But drain the gas out first!!!


(don't ask me how I know this....)

[Richard Hillsid]

Actually …. Fill it up with inert gas or water first, I imagine even filing it up with gasoline would be safer than welding an empty tank they blow easy as the gas to oxygen ratio is better for igniting, the gas comes from the last drop you could not get to drain out.

[marshmat]

Good point Richard.
ALWAYS purge a fuel tank with water (no common gases will fully displace fuel vapours) before working on it. Even something as innocuous as tapping new threads for the sender gauge can create enough of a spark to blow the thing up.

[jimslade]

if you want to glass make sure you use epoxy and cloth even if you have a pinhole later you will have a safety backup.

[jfc6570]

thanks everyone , preasure test first , then remove
"they are 180 gal a peice" , and weld , if needed , i have rebuilt boats for almost 20 years , it is really nice to be able to get second opinions , i have found one thing the internet is good for

do you know how to press test?
when we get survey we always use manometer, which is simply a loop of clear tube half filled water, put 2psi in tak, and watch water go up in the second half of loop, should rise to 8 feet head, ok, then leave it settle, on cold day water will drop and hot will rise, but water should stay there, if drops and drops and drops , hey your tank it not tight,
i had to do this for all my yachts in survey, same way they test a liferaft!!
no good just testing soap and water, this will find the big leaks, only manometer will be a true test
no charge for this info)

oh you,ll need valves in line , just one at hose to tank!!

[jfc6570]

thanks much