advice on tstat.

[demaris]

so i'm replacing the tstat on my 1994 7.4L mercruiser engine. i see 140 and 142 degree versions and some automotive ones that according to the forums look good on the meter but leave you with overheated manifolds.

any brand, degree suggestions?

also, i see that mine has a 13psi radiator/hxger cap. too low or what? some newer 454's are running 16psi. why i'm asking.

 

[Scott Danforth]

STANT for the T-stat (or packaged Mercruiser)

per your factory manual

140 F with raw water cooling and carbs
160 F for HX cooling and carbs.

factory pressure cap is 13 psi.

 

[alldodge]

Manual 16 (1993 to 1997, 454 & 502) list 16 psi cap for closed cooling

 

[demaris]

good info, thanks

 

[Scott Danforth]

the HX's left the factory with 13psi caps for many years. there was a mix of 13, 15, and 16psi caps standard starting in the late 90's depending on which supplier Mercruiser was purchasing from (Monitor Products, Sen Dure, or Champ)

as AD pointed out Manual does state 16, however your 13 psi cap will be fine

Champ products p/n for 16psi cap is 300157 (STANT cap) that was supplied going back to about 2001

HX is pressure tested to 40 PSI
torque for the HX end caps is 10-12 ft-lb

 

[demaris]

good info, thanks