Thermostat dimensions

[Walter Pearson]

I have seen specifications for the depth of the thermostat boss from 0.40 to 0.50 in. from the housing base datum. Is the tolerance this large or is 0.50 in. preferred (as in the original Atomic-4 Newsletter)?

Also, I had a machinist bore out the original boss in order to use a brass bushing for a new face, but when I got the t'stat housing back, the entire base looks shiny like it might have been also machined. This would reduce the depth of the lip where the t'stat sits. Can anyone tell me what the depth of this lip should be so I can compare? (Unfortunately, the machinist is not available to ask just what he did.)

[Don Moyer]

Walter,

This may be a sign that I've been in this business too long, but I don't ever recall writing anything about the depth of the groove in the underside of the thermostat housing.

I found several rather crude Universal shop drawings of the housing, but none of them specify the depth of this groove.

I measured the groove in our own aftermarket housings, and they measure .060" deep. When I slip a new Westerbeke thermostat into the groove, it appears to be "comfortable", with what appears to be .005" wiggle room, much of which will probably be taken up with a bit of crush on the gasket between the housing and the head when the stud nuts are torqued.

Hope this helps,

Don

[Walter Pearson]

Thanks. My recess measures 0.050 to 0.060, so there must not have been much of the surface removed. Probably more like I'm just catching some scale at the 0.050 spots. I'll just clean it up a bit and check the fit with the thermostat.

On the depth of the shut-off boss, my fix with a brass bushing is measuring 0.454 below the surface. I can still adjust either way, but am assuming this would be adequate.

[Don Moyer]

Walter,

I'm not sure how you're measuring to obtain your .454" dimension, but the bottom of the incoming by-pass port should be located a nominal 1/2" above the lower surface of the thermostat housing.

Don