Mercury KD-4 Cast Aluminum gas tank seam leak

[Buccaneer]

I replied to a year old thread of Louis “Green Thumbs”, but it doesn’t appear that
replying to an old thread “brings it to the head of the queue. Therefore, this is
for Louis or anyone else that’s attempted repairing a seam leak on the KD-4 style tanks.
——————–
Louis, I’ve been reading your old thread on fixing up leaking Mercury cast aluminum tanks.
I have a KD-4 that’s weeping along the seam.

Just wondering how all your hard work turned out when the tanks had the
test of “time and gasoline” in them?
Wondering if I should follow your path you outlined nicely, or buy some gas
tank sealer?

No idea if my tank bolts will turn, and if they don’t, I’m hesitant about breaking
any off…….. I have no milling machine! The tank has gas in it now, so
torching the bolts may be an issue as well!
Thanks.

The KD-4 in question running last October…..

https://youtu.be/KtNcklvpv2E

Prepare to be boarded!

[green-thumbs]

I have been into about a dozen of the cast aluminum tanks, I was very fortunate to run into the easy to do ones first. Later on I rand into tanks
with warped or corroded flange surfaces, broken studs and shut off
valve. All problems were resolved and tanks resealed.
Did I know what I was doing when I started…nope…had to figure things
out as I went along. Sometimes you do need a welder to add back a little metal to repair a crack or fill in a drilled out stud hole or gas valve hole
I have the advantage of a lot of odds and end collected over the years;
The motto in my shop is “What would McGyver do?” Junk I picked
up decades back sometimes is just the right thing to solve a problem…
sometimes the first solution proves unworkable, but, in the attempt
the solution that will work becomes clear.

How long will the reseal hold up over time? I don’t know, probably long
enough to outlast me. I think it will depend upon my workmanship more
than material used, I have had to redo a tank that failed to seal the first
time ,but, that was due to an error on my part.
Currently I am working on a cast aluminum tank from a 1941 Sea King
single made by Kiekhaefer. I have it cleaned up and tank flange surfaces sanded flat and smooth. Sometime in past its had a seam
leak repair attempt…drilled 2 holes thru tank halves from top to bottom
Threaded rods were used to pull tank halves together in an effort to
stem the leak. A different way to do things, but, if it solved the seam leak it also made for 4 new ways for tank to leak.

Louis

• This reply was modified 4 years, 3 months ago by green-thumbs.

[green-thumbs]

I do not know how long reseal will hold up. I suspect workmanship matters more than material. Kiekhaefer sealed tanks have held up very
well as most do not leak even after 7 or 8 decades
The 1941 Sea King tank in photos shows evidence of a repair method
not often seen. The holes drilled thru the tank had threaded rods to draw
ends of tank together…may or may not have worked. One thing certain.
it made for 4 new places to leak.
The other tank is an early pattern without the fore and aft hex
head screws and a small boss for gas shut off valve. Could be for a
prew war or early postwar twin with a rope plate starter.
Resealing a leaky tank seam by splitting the tank, removing old gasket
and sealant, cleaning and if needed sanding tank flanges level is low
tech and low cost. It can get a little hairy if your break a stud, not the end of world, just more work, If anyone is interested I have a photo
series of how to drill out a stud broken off flush. McGyvering at its best,
Louis

• This reply was modified 4 years, 3 months ago by green-thumbs.

[Buccaneer]

Thanks for your reply.
I was confounded looking at my tank and seeing only four fasteners that are
suppose to keep the whole seam from leaking. Wonder what they used
75 years ago for a sealer…. must have been good stuff!

Prepare to be boarded!

[green-thumbs]

Kiekhaefer cast aluminum gas tank evolved, apparently in response to problems with early tanks, The twin tanks come with and without the fore
and aft hex socket screws. several variations of fuel outlet boss, and
perhaps a bit more metal here and there. Rewind starter requires 4 screw holes in upper tank half to mount starter.
Tanks for single cylinder models also have variations.
We are probably better off not knowing what went into tank sealant and
gasket. I assume the worst and work and work over wet newspaper
when removing old gaskets then wet mop,
Louis

[billw]

I will just add my two cents to this. When I split my tanks open, I take them to an automotive machine shop. They have a giant, horizontal belt sander. It’s very purpose is to true up slightly warped parts. I give the guy twenty bucks and the tank halves are as true as the day they were made, in about five minutes. Also, the last tank I did was a WD3S Wizard. Rather than fuss with a gasket, I tried an experiment and used that red, jelly donut-like, anaerobic sealant, the same stuff used on crank case halves. It is known to stand up to ethanol, at least as good as anything can. I let it set up for a week, just to be sure to give it the best chance at success. I ran the motor at the Lowell Mass meet in September, for at least an hour straight, with no leaks evident. Going forward, I think I will do this again. It was much easier than the gasket method.. It “seams” to work, if you’ll pardon the pun.

Long live American manufacturing!

• This reply was modified 4 years, 3 months ago by billw.

[Buccaneer]

Bill, thanks for your input. First I’ll see if I can get the bolts or nuts to budge that
hold the tank together. I know of no big belt sander in these parts, but wish
I had one bigger than my 4″ a few times!

I’ve had good luck so far with “gas tank sealer”, and if planned ahead, a
little $25 can could be used to seal two or three tanks, so that’s always
an option as well if things aren’t going well taking the tank apart.

While lying in bed, I was wondering about omitting the gasket as well,
and using something like Yamabond 4 sealer, for the crankcase halves. Not sure
what it’s specs say about gasoline though.

Prepare to be boarded!

[green-thumbs]

There are several ways to skin a cat…the method I use involves old school technology, I have run into a tank sealed only with a sealant without gasket. Strong bond and it did not leak, but, tank was damaged
so it had to be split to repair. What ever it was it did a GREAT job.
I have also had a tank with all seams welded…that one would never
leak. Some attempted remedies for a seam leak failed to solve the
problem or introduced new problems.
Louis

[green-thumbs]

What do you do if you snap off a stud while splitting open
a cast aluminum tank.. out of the box thinking required
Fasten tank halves together using the other
bolt holes. Make a snug fitting drill sleeve to guide
drill into broken off stud….I used several different
sleeves to drill successively larger holes.
CHECK what drill is doing by taking tank apart
to be sure drill is not wondering.
Do NOT drill into threads.
Tap new thread also using tank to align
tap so it creates a thread straight and true.
I did not attempt to back out the remains
of stud. I had used up my supply of good luck
getting things acceptable…going for perfect
involved risking all I had gained.
Louis

• This reply was modified 4 years, 3 months ago by green-thumbs.

[Buccaneer]

Good idea Louis using the guide and tank top for drilling alignment.
I have not tried anything on the tank yet, but plan it after I’m done
with the lower unit. Thanks for sharing.

Prepare to be boarded!

[Author]

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