Replacing thermostat on (very) old Mercruiser 120

[justthisguyyaknow]

My manifold is this very old style (see attached image).

It appears that my (only) thermostat is (regrettably) located at the back of the manifold.
3 questions:

1. A simple logistical question: Aside from taking the entire manifold off and building a stand for it to hold it in a position such that the thermostat well in the manifold is pointing straight up, does anyone have any suggestion on what could be used to hold the thermostat in place, centered in the hole, long enough to re-assemble the end?
2. Is the diagram correct that the thermostat goes "under" the gasket (relative to the manifold)?

 

[Scott Danforth]

pull the elbow

use a pliers to pull the thermostat

scrape the gasket material

use a new thermostat (it will hold itself just fine)

install gasket and elbow

 

[justthisguyyaknow]

Actually, it's out of the boat right now, so I can (and probably will) just find a way to hold it upright. But in the future, it would be nice to be able to replace it without pulling the manifold (though not a huge deal).

Here's a video of the thermostat, which is just loose in the hole.

0 new items by pzeller1

photos.app.goo.gl

The thermostat is a Quicksilver 8M0089715, a fairly standard looking thermostat.

 

[Scott Danforth]

you only need to pull the elbow

the gasket will hold it fine

 

[justthisguyyaknow]

Then I must have the wrong thermostat, as nothing holds it in place. Once the elbow is tightened down, I suppose friction would hold it, but I can't see how, with the manifold installed on the engine, one would keep the thermostat from falling down by gravity before the elbow can be installed??? The gasket has no effect on it, as in the attached video, it's free to move about.

0 new items by pzeller1

photos.app.goo.gl

 

[justthisguyyaknow]

To be clear, this is a 35891 manifold and a 35892 exhaust elbow, 1963-66. It's officially used for a 110, but apparently was also fitted to 120's and possibly others. I've attached a good picture of this model manifold and elbow. I know exactly where the thermostat goes on this (nearly 60 year old) unit, I just need to know how to keep the thermostat in place long enough to re-attached the elbow. I'm assuming some type of sealant would hold it in place, but don't want to use anything which could cause any blockage.

My earlier video shows that the presence of the gasket does nothing to rectify the basic problem (gravity).

 

[1960 Starflite]

Now that is strange. I'm sure you've looked, but is there an undercut/counter bore on the manifold side?

 

[justthisguyyaknow]

There is a bit of a counterbore (somewhat rusted, though). I've decided not to perform electrolysis on the manifold because I've read that will just give fresh clean metal and may actually accelerate future rusting.

I did have someone recommend using a bit of Permatex aircraft sealant to help hold the thermostat in place, and I will. I think in the future I'll just remove the manifold each time I wish to replace the thermostat, supporting it on end. This will give me the added advantage of being able to ensure the rust hasn't progressed too far (I don't want to end up with water jumping into a cylinder through an exhaust valve causing hydro-lock!).