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Old 29-09-2018, 17:25   #16
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Re: Thread sealant on engine anodes?

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Originally Posted by a64pilot View Post
You won’t need it.
If you think you do use just a little bit of Teflon tape. You need to keep electrical contact of course, but I don’t think Teflon tape will isolate it, you could check with a multi meter if you were concerned
This is the practical answer; to repeat - you don't need it but a little Teflon tape won't stop the anode working.

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Originally Posted by boatpoker View Post
Break or interfere with the electrical connection between the heat exchanger housing and the anode, and your anode will have reduced effectiveness or be completely useless.

There must be 0.0ohms between the anode and the heat exchanger body.

The only way to test that is to install it, remove the end cap and then measure resistance between anode and exchanger...... more trouble than it's worth.
This is theoretically true and I note several Yanmar manuals state "do not use any sealant when fitting an anode".

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Originally Posted by Ecos View Post
Dielectric grease is used in all kinds of connectors these days. It doesn't seem to cause any problems in some really complicated electrical systems.
Quite correct and mainly because most dielectric greases are "very low pressure" greases which allows the grease to squeeze out between the contacts with minimal force thus maintaining electrical contact while sealing the interface from moisture etc. Of course, not an issue with a anode

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Originally Posted by boatpoker View Post
No. you've got it backwards. An ohmeter is quite capable of finding resistance in the ranges we are talking about. i.e. 0.0 ohms is ideal but anything less than 1.0ohm is acceptable. There is absolutely nothing on a boat that requires readings in the megohm range. Even AC ground leakage (potentially fatal) testing requires nothing higher than the kilohm range which is also within the capabilities of a $20 meter.
While any ohmmeter is suitable for checking the anode resistance, the emphasised section is really bad advice and while off-topic, it needs to be addressed. A Megger tests insulation resistances by applying a high voltage to the circuit under test, often in the order of 600V to ensure that insulation is not breaking down with working voltages. An $20 multimeter will be using a very low voltage to measure in the kilohm range and as such is not suitable for measuring AC ground leakage etc.

Back to the OP and the anode, I have done some empirical testing of how much resistance is added to a thread when using thread sealants and although the results vary with the type of sealant used, most add very little resistance - like in the order of a few tens of milliohms which is inconsequential in your situation. You need a lo-ohm or bonding meter to measure such small resistances, not a common multimeter.
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Old 29-09-2018, 17:28   #17
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Re: Thread sealant on engine anodes?

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If the thread sealant causes any resistance you would need a meter that reads less than 1 ohm. The usual onboard meter does not go below 1 ohm, it only goes up from 1 ohm.
Correct and really you need to be looking values between 0.1 and 10 milliohms; this requires a lo-ohm or bonding meter.
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Old 29-09-2018, 17:35   #18
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Re: Thread sealant on engine anodes?

All engine anodes I have seen use either a soft copper washer or a tapered thread to seal; makes sealant or tape unnecessary.
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Old 29-09-2018, 17:51   #19
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Re: Thread sealant on engine anodes?

[QUOTE=Wotname requires a lo-ohm or bonding meter.

I thought you could get a hand held meter that does everything, both high and low resistance?
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Old 29-09-2018, 18:02   #20
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Re: Thread sealant on engine anodes?

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Originally Posted by a64pilot View Post
If your talking pencil zincs you can only measure from the cap to the anode before installation and the cap to the metal it’s installed in after.
However I’ve never done that not even once, never heard of anyone doing it.
Exactly my point. Unless you measure that, you have no idea of the effect of telfon tape or pipe dope.
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Old 29-09-2018, 18:19   #21
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Re: Thread sealant on engine anodes?

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Originally Posted by Wotname View Post

While any ohmmeter is suitable for checking the anode resistance, the emphasised section is really bad advice and while off-topic, it needs to be addressed. A Megger tests insulation resistances by applying a high voltage to the circuit under test, often in the order of 600V to ensure that insulation is not breaking down with working voltages. An $20 multimeter will be using a very low voltage to measure in the kilohm range and as such is not suitable for measuring AC ground leakage etc.
Not so. You may want to read up on ESD and preventative measures including how to measure. This is well within the scope of a $20 meter.

- Shore cord unplugged (must remove water path)
- attach one lead to DC ground, preferably engine negative or it's bus, the other to an AC ground (receptacles work).
- (using the ground lug or sleeve on shore power cord male plug will also include the cord and shore inlet receptacle in the test.
-Should read less than 1ohm.
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Old 29-09-2018, 18:23   #22
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Re: Thread sealant on engine anodes?

[QUOTE=Ecos;2731584][QUOTE=Wotname requires a lo-ohm or bonding meter.

I thought you could get a hand held meter that does everything, both high and low resistance?[/QUOTE]

Yes, absolutely for everything that's required on your boat. Most meters from Harbour Freight will suffice. Megohms on high power insulators are a different world.
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Old 30-09-2018, 10:33   #23
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Re: Thread sealant on engine anodes?

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Originally Posted by Bill Seal View Post
Megohmmeter, as in Megger, used to measure Millions of Ohms of insulation resistance ???
Even a cheap Harbor Freight multimeter measures tenths of an ohm, enough to ensure contact,
Is I recall a megger is for detecting high potential shorts. I'm not sure it is applicable here?
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Old 30-09-2018, 10:41   #24
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Re: Thread sealant on engine anodes?

Just a touch of anti seize compound.
No t-tape.
Cheers,
SV Cloud Duster
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Old 30-09-2018, 10:48   #25
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Re: Thread sealant on engine anodes?

You dont need to measure ohms at all. Just continuity.
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Old 30-09-2018, 11:19   #26
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Re: Thread sealant on engine anodes?

[QUOTE=Wotname really you need to be looking values between 0.1 and 10 milliohms; this requires a lo-ohm or bonding meter.



I thought one meter could measure both milliohms and megohms, but I guess not. A bonding meter might be interesting to have on the boat?
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Old 30-09-2018, 14:09   #27
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Re: Thread sealant on engine anodes?

You don't need a meter because you shouldn't put ANYTHING on the anode threads. They are made with a "pipe thread" so the taper will cause the anode to seat . Just DON'T use every ounce of strength you can muster to tighten. In fact you should check the threads to be sure they are clean so there is 100% metal to metal contact. Don't overthink it. JMHO
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