Pulled stud when meant to remove nut on thermostat housing.

[hanleyclifford]

The stud in the picture looks a little suspect. Make sure it isn't some metric substitute. Get a new clean 3/8x16 nut and check the threads. There is no harm in going in a little deeper on the block but be sure to use permatex #2 (the goo) to seat the stud. It is ok to use regular 3/8x24 nuts on the two housing studs - never use lock washers. Use 9/16 socket on nuts.

[BunnyPlanet169]

1) The nut is currently seized to the stud. I used heat (although maybe I could have used more head), penetrating oil (the good stuff, not WD40). I've slightly chewed up the sides of the smooth part of the stud, but the nut didn't go anywhere.

The MMI manual section on thermostats just says, essentially, "put the thermostat housing back on and tighten up the nuts" with no mention of the fact that these nuts are in fact holding on the head, which might be worth a mention. I assume I need to follow the full procedure in the overhaul section, tightening the bolts in stages until I get to 35 ft-lbs?

I would not reuse it unless I could loosen it up.

IMHO, the use of the head studs for thermostat housing mounting is a design weakness. That said, it's been working for 40 years or more. I've always just tightened them, and frankly, not always with a torque wrench....

[StephenGwyn]

I'm not going to reuse it. I bought a new one at an autoparts store and pulled an old one from the "spare" block sitting in the shed. Back to the boat on the weekend. Also, at the autoparts store, I bought a socket with slightly thinner walls which fits just exactly between the thermostat housing and the nut, so I don't need to spacers or shoulder nuts.

SG