A warning and a request for help.

[boatnut]

We have started some work on our 1969 18' H&M classic. The plan is to rebuild the 302 and that is underway (stroke to 331, GT-40 heads, keeping the H&M externals). Our goal is to have the boat look exactly as it did when it left the factory in 1969 (it is already in awesome condition). We already took care of some (typical for a 46 yr old boat) transom and stringer glass/coring issues. Rewiring the entire boat, painting drive, etc. etc. etc. etc. We decided not to remove the deck and change the tank for many reasons. However we just discovered something, we have not used the boat in over 10 years, it has been covered and indoors, but we left gas in the tank. When we went to pump out the tank yesterday we discovered a thick coating of a varnish like substance on the tank bottom (removed the sending unit for visual access). Also the gas pick up is seemingly plugged with this substance as we cannot blow any air into the tank from gas line back in the engine area -- it seems to be solidly plugged. This substance is thick tough and difficult to remove. So based on this:

1) the warning, we really screwed up leaving gas in the tank, if a boat is going to sit around for years (actually we never thought it would go unused for so long but it did) you have to remove the gasoline from the tank(s). I am not sure how much was in there and how much evaporated but we removed the liquid in the tank and it was only a couple of gallons --with much residue left behind.

2) the request for help: does anyone have any idea what we can do to recover from this blunder? Short of removing the deck and changing the tank. We dug some of this gunk out of the tank and experimented with it. Diesel fuel doesn't seem to effect it. Gasoline does little to effect it. Acetone seems to effect it slightly. MEK seems to have the biggest effect on it and will dissolve chuncks of it. Hot water seems to soften it but not completely dissolve it (only tried for 10 minutes or so). Vinegar (based on a suggestion found on the internet) seems to have little or no effect. I haven't tried carb cleaning solution.

I guess we could try dumping several gallons of MEK in the tank and letting it sit for a few days and then try pumping it out. Nasty and dangerous stuff to work with but it seems to dissolve the gunk. However I don't know if it will have enough access to the solidified varnish in the gas line pickup to be able to clear that. We would love to find a feasible and safe way to clean out this tank without changing it. You all know where this tank is and how it is difficult to access. Any ideas? Thanks very much in advance. Ed

[BUIZILLA]

I can tell you from over 40 years in the fuel biz.... your NOT going to get the tank as clean as you would like, or need..

[mattyboy]

I wish there was an easy way around this but a 69 would be a steel tank and is way beyond its lifespan. I have seen early 70s boats with alum tanks fail the fuel system needs to be upgraded to handle today's fuel
Try rubbing alcohol on the sludge and see what it does . if it breaks it up today's fuels will do the same And all that stuff will be fed into the motor The gas tank, lines and anything rubber that handles gas need to be replaced

As far has splitting the deck it is not that big a job a few friends or some college engineering makes lifting the deck easy. It just makes sense if you are doing all other things right why not do the fuel system right

[yeller]

As Matty said....it's not as big a job to split the deck as most people think. If you just want to pull the tank, you might not even have to disconnect any wiring. Jus open it up like a clam.

[Greg Guimond]

You might also consider carefully removing some floor and then the top of the tank enough to get a rubber race bladder tank in there. It would take some research and careful forethought but be less overall effort than a full removal.

[gcarter]

You might also consider carefully removing some floor and then the top of the tank enough to get a rubber race bladder tank in there. It would take some research and careful forethought but be less overall effort than a full removal.

Greg, GEOO had a bladder in Mighty Mouse. I read in one post that you could smell gas using it.
Also, bladders are EXPENSIVE! Maybe you could buy 2 aluminum tanks for the price of a bladder.

[Morgan's Cloud]

Many years ago my brother bought in a used , but in very good shape , CC XK19.
He had the exact same problem. I'd never seen anything like that stuff before. It was like brown tar and nothing broke it down or got it out of the lines.

In the end he had to remove the tank , which was a shame as it was galvanized and in as new condition , and all the fuel lines and filters and replace them .
Yep , new tank !

Buiz and Matty are right . If not done properly now you never know where you'll be left stranded later on down the road as the residual globs work their way backwards (that's if you can even remove the obvious stuff)

[gcarter]

Ed, stop and say to yourself, "Pulling the deck is easy and the right thing to do".
If you had all your stuff together, you could do it in 24-36 hours.
But you might as well take advantage of the convenience while it's off.

[Greg Guimond]

Greg, GEOO had a bladder in Mighty Mouse. I read in one post that you could smell gas using it.
Also, bladders are EXPENSIVE! Maybe you could buy 2 aluminum tanks for the price of a bladder.

The technology has advanced tremendously over the last 5-10 years so I would not be concerned with that at all. But you are correct George that they are a little pricey. The thing about pulling a deck and then a tank though is that you always find more to do and more costs along the way.

[mattyboy]

there are always things to drop money on in a boat but this sounds pretty much like my 16 it was good cosmetically and structurally so I had help pulling the deck i did do some minor stuff with the deck off paint the bilge and get a new starter which is a bear with the deck on. After that I knew the boat was good to go for many more years it will give you piece of mind.

[joseph m. hahnl]

Try Turpentine or denatured alcohol MEK is explosive and a skin irritant.

[boatnut]

Ed, stop and say to yourself, "Pulling the deck is easy and the right thing to do".
If you had all your stuff together, you could do it in 24-36 hours.
But you might as well take advantage of the convenience while it's off.

Lots of good advice and responses. I am also not optimistic about cleaning this tank or lines sufficiently to have acceptable boat usage going forward. In addition there is the risk of the tank being close to corrosion failure (no way of really knowing with crevice corrosion). And George (my trusted guru) if I had my "stuff" together I wouldn't even be working on this boat -- it belongs to my son now. However that is not true as we both are motivated to make it a perfect 69 H&M 18, one of the best boats on the planet and it is a family project. We are somewhat blown away by tearing the deck off of this boat and what it might entail. (However cleaning this tank might be a more difficult job.) One question, when you remove the deck (I have read some of the threads on this), are the deck and hull flexible and unstable to the extent that it is difficult to get the shapes aligned sufficiently to get the deck refastened and everything in the proper alignment. Or in other words, is the deck easy to put back on, or is it a challenge? Ed

[mattyboy]

They are flexible but pretty strong you are not removing bracing so the bottom won't loose it shape . the deck needs a little more attention the real lifting should take place near the cockpit 6 people do the job nicely 2 on each side by the cockpit one in the hatch area and one on the nose the people on the nose and the hatch only support they don't lift some milk crates and tires will do to rest the deck on .

I had 6 iron workers after 2 cases of beer get the deck back on I thought for sure the deck was going to snap my 16 was not cored only glass so it was flimsy it went back on no issue at all

[jl1962]

Here are some links to the deck-off tank replacement on my old boat.

http://www.donzi.net/forums/showthre...ght=deck%20day

http://www.donzi.net/forums/showthre...Deck-off-Day-3

http://www.donzi.net/forums/showthre...ght=deck%20day

This was performed by the previous owner so I can't make any representations as to how easy it was or wasn't. But to echo others, the peace of mind and potential safety is worth it. And no point in doing a lot of engine work only to sort out endless fuel issues.

Good luck and keep us posted.

[gcarter]

Ed, you may or may not have noticed, I sat the 22C deck on two small folding scaffolds I bought at Harbour Freight , or somewhere. One under the foredeck just in front of the cockpit, etc.
Then I went a bit more minimal, and replaced the rear scaffold w/a cinder block sitting on top of a furniture dolly which was placed under the battery box.
It worked very well and the price was right.

The hull is stable enough so that the 22C sat on dollies (and not a trailer) for several years and then went right back together.