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boatnut
03-26-2015, 02:51 PM
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
03-26-2015, 03:23 PM
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
03-26-2015, 03:31 PM
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
03-26-2015, 03:43 PM
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
03-26-2015, 04:22 PM
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
03-26-2015, 05:34 PM
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
03-26-2015, 05:41 PM
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
03-26-2015, 05:44 PM
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
03-26-2015, 06:28 PM
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
03-26-2015, 07:51 PM
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
03-26-2015, 07:51 PM
Try Turpentine or denatured alcohol :kingme: MEK is explosive and a skin irritant.:boggled:

boatnut
03-26-2015, 08:17 PM
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
03-26-2015, 08:35 PM
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
03-26-2015, 08:44 PM
Here are some links to the deck-off tank replacement on my old boat.

http://www.donzi.net/forums/showthread.php?35831-Deck-Off-Day-1&highlight=deck%20day

http://www.donzi.net/forums/showthread.php?36402-Deck-off-Day-3

http://www.donzi.net/forums/showthread.php?36558-Deck-off-Day-4-5&highlight=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
03-26-2015, 09:12 PM
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.

yeller
03-26-2015, 09:42 PM
We are somewhat blown away by tearing the deck off of this boat and what it might entail. ....... 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? EdI was concerned about the work it might take to get my deck off also, but once I got into it, I was "blown away" by how easy it was. I had help removing the deck, but using this method, I was able to reinstall completely by myself. If you have an overhead hoist, it'll be even easier.

Greg Guimond
03-26-2015, 09:49 PM
A backhoe works well also. I guess if you want to really have an "original boat" it's time to take off its head!

boatnut
03-27-2015, 12:08 PM
Thanks to all, you continue to make a strong argument to just spend 10 minutes ripping the deck off and proceed with a new tank. Or maybe it will take a little longer. It looks like there is some sort of sealant or adhesive at the deck-hull joint, what is that (it is close to white) hopefully not 5200? Is this adhesive difficult to separate once you get all the screws (and glass tabs) off? Ed

mattyboy
03-27-2015, 12:36 PM
All the older classics I have seen didn't have sealer around the deck hull joint
There were glass tabs holding the deck in place around the inside of the floor locker and around the ski locker area. Remove the rub rail screws then the deck screws cut the tabs and lift

Take a utility knife to it see how tuff it is usually you see sealer as a repair for rub rail screws that loosen up and are stripped out

smidgen too
03-27-2015, 01:07 PM
I have used E-85 to clean out Sludge out of the aluminum fuel tanks in one of my Magnums, it can cut through even the hard crud making it easier to pump out . I would hate to see what will happen to engines & fuel related parts when that's the only fuel we can buy.

mattyboy
03-27-2015, 02:46 PM
I have used E-85 to clean out Sludge out of the aluminum fuel tanks in one of my Magnums, it can cut through even the hard crud making it easier to pump out . I would hate to see what will happen to engines & fuel related parts when that's the only fuel we can buy.


damn straight :yes:

just think what ethanol does to 45 year old lines and hoses

boatnut
03-27-2015, 04:06 PM
Hi Guys, been looking through the forums reading deck off and tank replacement info -- pretty amazing how many great Donzi's have been saved from landfills by you guys on the forum. Good work. I haven't found specific tank drawings yet, but what I have read implied that I could use the standard 18' classic 25 gallon tank to replace the one I have or if I am willing to move the rear bulkhead back I can use the later 18' classic 41 gallon tank. These tanks would work and I wouldn't have to take measurements from my current tank and have it reproduced to exactly the same dimensions. Does that sound correct? Of course I would talk to the tank builder and make sure what they were providing seems to be close to the "hole" I have to put it in. And one other question, does anyone know approximately how much longer (how far do I have to move the rear bulkhead) the 41 gallon tank is than the 25 gallon tank? While this task (tank change) seems like a big complex job, it at least seems doable ---I do not have that feeling about cleaning the gunk out of the old tank, so thanks for the guidance. Ed

mattyboy
03-27-2015, 04:45 PM
some more thoughts is the original size 23-25 gallon tank too small for your boating style?

Bigger is not always better with today's fuels and the risk for phase separation the less fuel onboard at any given time the better especially if the boat is not used all the time . But if your boating style calls for doubling your range then go for a 40 gallon tank.

If you want a little bigger tank research Rootsy here he had a taller tank made that fit in the original footprint for his 18 project


Florida marine tanks makes a FMT 23 DZ they were an OEM for Donzi they will build a tank for you and send you a drawing they will add ears or any other items you may want you sign off on the plans and they build it . so make sure you get what you want and make sure if there is a sight glass vent and fills match what you have

gcarter
03-27-2015, 05:48 PM
Ed, I did this to an 18C.........http://www.donzi.net/forums/showthread.php?49388-vonkamp-s-Barrel-Back-18
When Barry delivered the hull, the aft tank bulkhead was already gone...don't remember why.
I could see where the old bulkhead had been and I simply located the new rear bulkhead about 1" aft of the new tank rear end location. I don't remember for sure, but I seem to remember the bulkhead moved back about 11". This is a very easy change to make.
Below is a 41 gallon PDF. You should be able to find a local tank MFGR. I'm sure there's no need to send one from the East coast.
The other item that changes is the 'glass center hatch liner. Isn't yours glass, or is it molded black flexible plastic?
If it's 'glass, I could modify it to fit w/the new tank for a modest price.

Greg Guimond
03-27-2015, 06:13 PM
Thanks to all, you continue to make a strong argument to just spend 10 minutes ripping the deck off and proceed with a new tank. Or maybe it will take a little longer. It looks like there is some sort of sealant or adhesive at the deck-hull joint, what is that (it is close to white) hopefully not 5200? Is this adhesive difficult to separate once you get all the screws (and glass tabs) off? Ed


If a prior owner used 5200 to seal the deck joint your world just changed. I can't imagine someone would do that but we have all seen stranger things done. Hopefully it's just some type of painters caulk. Good luck :yes:

boatnut
03-27-2015, 09:46 PM
If a prior owner used 5200 to seal the deck joint your world just changed. I can't imagine someone would do that but we have all seen stranger things done. Hopefully it's just some type of painters caulk. Good luck :yes:

Hopefully not Greg, the deck has never been off of this boat. I bought the boat when it was a couple of years old (many moons ago) and nothing had been done to it. Whatever is there came from Donzi. Ed

joseph m. hahnl
03-28-2015, 09:52 AM
I ran into an issue in my cruiser where it looks like some one used Kreem Sealer in the port tank. The ethanol was not kind and the fuel turned milky white clogging the inline filter.:frown: I guess some times you got to buck up and do what needs to be done in the name of pleasure :kingme:

gcarter
03-28-2015, 04:53 PM
Of course the easy thing to do is remove one of the side rub rails, and stick a putty knife up into the joint.....
See what happens. It'll only take about 5 minutes.

boatnut
03-28-2015, 10:12 PM
Of course the easy thing to do is remove one of the side rub rails, and stick a putty knife up into the joint.....
See what happens. It'll only take about 5 minutes.

I agree George, I am assuming that what I see is not a big deal (not 5200) but I have not checked it out yet. I know it was done when they built the boat so I assume they would not put some onerous adhesive on that joint. (Hope might be a better word) The next thing we have to do is decide what size tank to go with. I saw your drawing of the 41 gallon tank and the end of that would extend into the access area where the tub sits. I don't think that is all bad as I think it is low enough (the tank and the new bulkhead) to be below the molded lip for the cover of this area which would allow extending the tank into the area and having the sending unit and pick up plumbing easily accessible. The area behind the tank could be used for some storage without using the tub (maybe with some floor boards to allow bilge water to flow under the area. I probably haven't explained this well but it is very clear in my mind :) . Anyway my son needs to pick a tank size (original 23-25 gal would be easiest of course) and then we can proceed. I have to take off tomorrow to take my three youngest grandkids to Monterey for spring break so I will have to pause the project for almost a week. Thanks for all of your continued info and guidance.

Ghost
03-28-2015, 11:55 PM
I've seen some stuff in old hull/deck joints that was white, think it was just caulking of some sort. Wasn't a big deal. Crossing my fingers yours isn't an issue.

Morgan's Cloud
03-29-2015, 06:59 AM
I've seen some stuff in old hull/deck joints that was white, think it was just caulking of some sort. Wasn't a big deal. Crossing my fingers yours isn't an issue.

I think you may be right .
Although mine's a bit older there was something in the joint as well that was whiteish . Whatever it was it was old and mostly ineffective . So much so that I believe the deck just popped off after all the screws , etc , were out without even messing with the sealer.

yeller
03-29-2015, 05:10 PM
If a prior owner used 5200 to seal the deck joint your world just changed. I can't imagine someone would do that but we have all seen stranger things done. Hopefully it's just some type of painters caulk. Good luck :yes:
My 2004 was sealed with what I believe was 5200. It really wasn't a big deal to seperate it. Just had to hammer a chisel between the deck/hull joint, then hammer a second chisel 6" in front of that. Remove the back chisel and repeat. Took about 30~60 minutes to break it free. I'd much rather have the bonding strength of 5200 than rely solely on the factory screws and some sealing silicon.

gcarter
03-29-2015, 06:45 PM
My 2004 was sealed with what I believe was 5200. It really wasn't a big deal to seperate it. Just had to hammer a chisel between the deck/hull joint, then hammer a second chisel 6" in front of that. Remove the back chisel and repeat. Took about 30~60 minutes to break it free. I'd much rather have the bonding strength of 5200 than rely solely on the factory screws and some sealing silicon.

It was probably 4200. It looks like 5200 but a lot easier to get apart.
Of course I through bolted the TR, in 209 places.
I used RTV for sealing.

Greg Guimond
03-29-2015, 07:16 PM
.
We added additional blocking to the 16 along the entire top edge of the hull.

Bonding this into place is easy when the deck is off boatnut and gives the bolts more meat for compression. Some guys cap the transom only and do away with a rub rail there. That's a fair amount of additional work.
.

gotboats
04-01-2015, 11:12 PM
I think the stock tank size is the ticket! I would like to pull the tank out and replace with a better tank that fits and is plumbed the same. As for the additional blocking along top edge of hull sounds like a very good addition. Hopefully we can get done before the new tank needs to be replaced... I am boatnuts son and the boat in question is mine. Thanks for everyone's input and thanks dad for all the time your spending helping me or is it me helping you...

Kirbyvv
04-02-2015, 09:44 AM
81872

I've attached the Florida Marine Tank FMT stock donzi 25 gallon tank. This may be what you want. Measure for the sending unit and pick-up locations. I had them relocated to line up with the floor access hatches.

boatnut
04-03-2015, 09:20 PM
My son Bill wants to go with the 25 gal tank, thanks for the drawing kirbyvv, I sent a note to FMT to get a quote and asked them a few questions. George, tried your test on the deck joint and it breaks free easily. It is definitely not 5200 or 4200, probably some type of caulk more for water blockage than adhesion. So we dodged one bullet. After getting the latest drawing we will chk some measurements and see if we can get confident enough to order a new tank before we remove the old tank. Thanks guys, Ed