Clamshell thermostats- I'm confused.....

[9D280]

Does anyone know when Merc decided to delete the thermostat from the Clamshell 50/ 60?

I ask becuase I decided to remove the exhaust / cooling jackets form the port side after I noticed one of the gaskets appeared to be being assisted by silicon sealant - turns out it wasn't- it had been totally replaced by same , however I was a bit surprised to find a thermostat in there....on an engine that no Microfiche seems to show one!

So, I had a "lateral thinking trawl" round good old Ishop's selection of info, and find that the manifold assy I have on my engine is off a "650" series machine. The livery on mine would hint it's a late 80s / early 90s. Makes me wonder - has it been rebuilt using parts off an older engine, or has someone done a cowl swap to make it look more modern / replaced a broken cowl?

So, does anyone happen to know the Clamshell thermostat history off the top of their heads? (or maybe a better question might be if I just rebuilt without the 'stat does it rely on the back pressure to make sure cooling water gets to corners it might otherwise not reach? (I hear they were prone to overheat, and I wonder if the 'stat was deleted to cure that issue?

[outboardtech]

have u the model and serial numbers

[9D280]

I wish!

The sticker on the clamp tells me it;s a "..ury" , and the disc that should be in the head is missing. The paintwork looks like it's never been touched, so I'm wondering if I read in another thread that military engines don't carry serial numbers? or is it a replacement after the original siezed itself? Not sure if the Navy used Merc 60's or not assuming that is the case......

Anyhow, what I can say is that having trawled the Microfiches, I appaer to have:

Either something in 6428681 THRU 0B122929, but with a thermostat that isn't on the Microfiche,
or something in the 4382057 THRU 4571651; 7073473 THRU 7087822, or 9112989 THRU 9135824 ranges with a fuel system from the newer engnes.....

I realise of course that parts can be swapped / upgraded etc, but the cowling is of this livery http://cgi.ebay.co.uk/Mercury-2-2-Ou...1%7C240%3A1318 if it helps ID it... (just the first one I found that's got the same paint job as mine!)

Any other telltale parts that might be able to assisit in narrowing it down?