Replacing both oil sending units as they failed, but hard to remove

[sdowney717]

They are so close to the block, I can't fit a wrench on them, and the shell spins.
I was thinking maybe some large water pump pliers and squeeze super hard might turn them out. And the starboard engine, this is hard to reach. They sit under the exhaust manifold. Worst thing, I will have to remove manifold and cut them off with a sawzall.

Most likely they are original to 1970.

They are Sierra dual station. I bought new ones and then coated the shell with JB Weld, plan to also paint them.
To prevent them being impossible to install or remove, I got 1/8" extenders off Amazon. These are 304 SS.
I bought SS as I thought what if they were brass and got hit, like maybe would snap off.

SS has a higher electric resistance, but the currents here are super low. And this is a good size chunk of SS. They will thread into cast iron block, and the sensor metal is steel, hope they don't leak. I would not use teflon tape, but I might use rector seal T Plus 2, which I don't think would block electric connection.
RectorSeal T Plus 2 in. 4 oz. Teflon Pipe-Thread Putty/Sealant 23633 - The Home Depot

Amazon.com: DERPIPE Forged Reducer Adapter Fitting - Stainless Steel 304 Reducing Pipe Connector, 1/8" NPT Female x 1/8" NPT Male (pack of 2) : Automotive

 

[sdowney717]

Yes the huge pliers worked good.
The starboard motor, had to drop the exhaust manifold just to see some of the sender.

They look very old. Made by Stewart Warner. Both damaged by rust on the inside, and looked burned. The fine wires inside had shorted.
In twisting them off the thin brass cover shell broke off the sending unit, exposing the internals.

The phenolic plate cracked and the rubbing point arm is doubled on both sides of the phenolic wire wound resistor board and is so very thin one had warped back.
They had been flakey foy years.

The SS extenders worked very well, was able to get a wrench behind them.
I tightened mostly with just my hand.

The new ones coated with JB weld, maybe will keep them from rusting out.
Decided paint not worth the bother.
Otherwise, after a few years, these things might have started rusting.

 

[gonzo]

Break them off with a hammer and then grab the stem. If they break close to the block an easy off will take care of them.

 

[debbie_holt]

Get those threads clean and really dry before you thread em in – corrosion and buildup matter way more than the SS/cast iron gap.

 

[HelmutSheina]

I have some concerns about the SS risers, though it is quite noble on the galvanic scale, it rusts here in the humid air and if you're around salt be really careful. You should be able to find a tap to clean the block threads with.

As far as thread sealing goes, thread tape is not a good sealant, it works more as a lubricant that allows you to tighten tapered threads harder without galling.

I prefer Permatex Aviation No. 3. It is resistant to most solvents and good for sealing gaskets, threads and metal to metal. I keep the smaller one one aboard and in the car because I feel it should be part of emergency equipment. I seem to recall that Mercury Perfect Seal is Permatex Aviation these days.