Can I add temperature switch here?

[kaliona]

1978 165hp I6. Purchased an engine alarm kit with oil pressure and engine temp switches. The new temp switch is 3/8" npt and just want to make sure I install it in the right location. There are two plugs on my t'stat housing, but they look like 1/8" or 1/4" npt. One plug is right next to the original temp sender below the t'stat, and the other plug is above right next to the t'stat. Which should I use for the new switch? Do I need to get a reducer? Or do I get a tee and mount both the sender and switch on the original port? Also can I just get whatever fittings I need from Napa or any old hardware store? Brass. . . stainless. . .does it matter? Pic of what I have is attached. Thanks

 

[Scott Danforth]

yes, and you get a pilot drill and a 3/8" pipe tap, and you open one of the holes to 3/8" NPT.

you will get false readings if you attempt an adapter or a pile of fittings.

 

[kaliona]

Thanks, I'll try enlarging and tapping the hole next to the existing temp sender. I hope there's enough meat there to do it.

 

[Fun Times]

http://www.mercruiserparts.com/Show...br=60&bdesc=EXAUST+MANIFOLD+AND+EXHAUST+ELBOW

Using either one of the three item (plug) numbers 36 from the link above, Merc OEM part numbers 22-32802 & 22-328022 = Sierra # 18-4263 that should be thread size, 1/8" - 27 NPT pipe plug.

OEM part number 22-32803 / Sierra # 18-4264 should be thread size 3/8" - 18 NPT pipe plug.

http://www.iboats.com/Mercruiser-Pi...1557639--session_id.187309188--view_id.270065

 

[kaliona]

Fun Times, would be ideal if one of those two plugs were 3/8". Unfortunately they're both 1/8". So I'm going to have to drill and tap one of them.

 

[JustJason]

Weatherhead makes brass adaptors with holes in the middle of them to allow for fluid transfer. This is a basic temp switch, I can't see why it wouldn't work.....

 

[Alumarine]

I have the same 47587 manifold as you on my 1980 3 liter.
On mine the plug to the left of the temp sender is 3/8 npt.
On yours it certainly looks smaller than that though.

On my 1974 3 liter the plug is smaller like yours.

 

[Fun Times]

I have the same 47587 manifold as you on my 1980 3 liter.
On mine the plug to the left of the temp sender is 3/8 npt.
On yours it certainly looks smaller than that though.

On my 1974 3 liter the plug is smaller like yours.

There seemed to be a change in plug size between serial number ranges back then.

36	22-32803	--PLUG, PIPE-WATER DISTRIBUTION BLOCK (click here)		SERIAL 00000000-03464447	$4.60	$4.49	1
36	22-328022	--PLUG, PIPE-WATER DISTRIBUTION BLOCK (click here)	22-32802	SERIAL 00000000-03464447	$4.90	$4.78	1
35	861493A07	BLOCK ASSEMBLY, WATER DISTRIBUTION-CYLINDER BLOCK	63908A2	SERIAL 03464448-09999999	$123.67	$111.49	1
36	22-328022	--PLUG, PIPE-WATER DISTRIBUTION BLOCK (click here)	22-32802	SERIAL 03464448-09999999