4.3 Replacing exhaust manifolds - ditch nylon drain plugs?

[ShoalSurvivor]

I’m replacing the exhaust manifolds and elbows that I previously replaced in 2013. All has been fine except for a cracked nylon drain fitting… fixable, but a real pain.

I read about changing that fitting to a 3/4” NPT brass elbow fitting, but stuck with the nylon.

Now, i’m installing a new set, and debating nylon vs brass again. Have other people replaced theirs? Any issues? Is the nylon specifically intended to protect the manifold?

What is the preferred sealant for the nylon elbow? I've been using nylon tape.
Also, what is the preferred sealant for the brass plugs on the unused ports on the manifold?

Thanks!

1991 Stingray 190LX Alpha 1 Gen II, with 2004 Mercruiser 4.3L 225hp 4bbl Quicksilver repower

 

[Scott Danforth]

Get the stainless plugs from Hardin marine

 

[Bondo]

Get the stainless plugs from Hardin marine

Ayuh,.... I made my own, a 1/2" x 1/2" stainless cap screw, 2, 1/2" ss flat washers, 'n a fat 1/2" o-ring,....
I tack welded the extra flat washer perpendicular to the bolt head, so I can spin 'em out with my fingers,....

I use Quicksilver Perfect Seal for 'bout 99% of any sealant needs,.....

 

[ShoalSurvivor]

thanks re: stainless plugs.
how about replacing the nylon drain fitting ?

 

[ShoalSurvivor]

I've read that nylon tape should not be used with nylon to steel fittings, because the material can bunch and prevent a proper seal. PTFE sealant is better for NPT threads because it is free to fill and expel. I also read:

"The right way to assemble a threaded plastic joint is to finger tighten, and then add no more than ½ to ¾ turn.".

Anyone know who's finger to use?

Interestingly, the elbows point opposite directions on the manifold, so one side will likely be 1/2 turn too loose or the other side 1/2 turn too tight.

 

[Bondo]

Anyone know who's finger to use?

Ayuh,..... Yer's,..... one finger, 'n one thumb, preferably on the same hand,....

 

[Scott06]

thanks re: stainless plugs.
how about replacing the nylon drain fitting ?

Have not had an issue with mine but replace the plugs every couple years. If you feel better replace them or upgrade to brass pipe thread fittings. You don’t neccesaarily need a drain plug can remove hose to winterize

 

[Scott Danforth]

I would use some silicone grease on the plug. The O-rings is what seals the plug.

I would use permatex #3 on the elbow theeads

 

[harringtondav]

My previous '96 4.3 LX's blue nylon plugs survived 25 years of winterizing.
Finger tight per @Bondo reply #6. No tape, no sealant. If they leaked I never noticed. 100% fresh water boating.