thermostat puzzel

[mark babb]

I am trying to replace the thermostat in my mercruise 260/350 engine. I bought one new with a gasket set which is confusing. The parts are the correct ones for the engine but there is one gasket that would totaly close the thermostat hole. Why would one completely close the water flow?
Another thin gasket with oblong bolt holes would just close the square hole part above the thermostat. Isn't this a bypass for the exhast cooling before the thermostat opens? There is one that would not close the square hole ( my guess this would be at the intake manifold) and one smaller gasket(cork) that looks like it would sit under the thermostat lip. There is a rubber O ring the size of the smaller gasket. I have no guess on this one. This is a raw water cooling setup with four hoses from the lower thermostat housing and two hoses from the cap. There was no thermostat in the thing from the start so I don't have the old one to go by. The thermostat does go under the two hose cap and not on the intake manifold itself, right? I have a manual but it is totally useless about gasket details. Also when are restictor gaskets used on the exhaust and when not? This is a center riser setup. Any help out there for this puzzel?

 

[Scaaty]

Re: thermostat puzzel

Just match the one that you have now...ignore the rest. I think its a Merc thing (and also why I own a 350 /Volvo!)

 

[DHPMARINE]

Re: thermostat puzzel

Just a guess,but if your motor is around 1986 - 1987 there are 3 cooling systems.You need to see pictures of all 3 to know which part numbers fit your motor.

DHP

 

[Nova II 260]

Re: thermostat puzzel

Mark,
i believe mine is like yours. There is also a sleeve that goes on top of the thermostat and keeps it at the bottom of the goosneck.
It's about .020 x 1/2" and the dia of the pocket the thermostat set in. This does not come in the kits...

On mine the extra square port was (and is) also blocked off by the gasket that is under the cap. (See the black gasket in the center)

I just opened mine up b/c I have no readings on the temp guage and the PO said there were no thermos in there... wrong. Troubleshooting that next week. good luck

 

[Don S]

Re: thermostat puzzel

Mercruiser used the 260 designation for the engine from 1978 to 1995. In that time, they used many different thermostat housings. Without knowing what year or serial number your engine actually is, it's hard to say. But if you had a 1987 or newer Mercriser 260 with a Design II cooling system, you would know why the blank gasket. Check out the link below and locate your year and also check out the design II in the 87 to 95 section.

http://dougrussell.com/partscatalog/collections/index.cfm?fuseaction=collectdetails&colid=04

 

[mark babb]

Re: thermostat puzzel

Thanks for the responses. The gasket kit is just like the one pictured. I see from the diagram on the link for dougrussell that it shows a open square hole gasket for the 1978 260/350 and the one above like mine closes it off. Which one is correct and can you tell me why. Do you have a part # for the hold down ring you picture?

 

[mark babb]

Re: thermostat puzzel

Thanks for the responses. The gasket kit is just like the one pictured. I see from the diagram on the link for dougrussell that it shows a open square hole gasket for the 1978 260/350 and the one above like mine closes it off. Which one is correct and can you tell me why. Do you have a part # for the hold down ring you picture?

 

[Don S]

Re: thermostat puzzel

Maybe I didn't make it clear enough.

WHAT YEAR IS YOUR ENGINE

 

[mark babb]

Re: thermostat puzzel

I did 1978 260/350

 

[mark babb]

Re: thermostat puzzel

Any response from Nova

 

[mark babb]

Re: thermostat puzzel

where did everyone go? Help

 

[Don S]

Re: thermostat puzzel

Nova probably went to bed, it's a quarter after 11 in Ohio.

From the looks of his kit, that is the wrong kit for your particular engine. Get the right kit and see how it works.

 

[mark babb]

Re: thermostat puzzel

THANKS ANY WAY

 

[Nova II 260]

Re: thermostat puzzel

Here ya go
Thermostat sleeve

# 13250 Thermostat sleeve $8.96

OEM# 23-47508T
catalog url

 

[Don S]

Re: thermostat puzzel

Here ya go
Thermostat sleeve

# 13250 Thermostat sleeve $8.96

OEM# 23-47508T
catalog url

That 23-47508T OEM number has absolutely nothing to do with a 1978 Mercruiser 260 thermostat housing.

 

[mark babb]

Re: thermostat puzzel

thanks for the help! I see the housing in the picture is completely different than the one on mine but the site I bought the same gasket kit as shown in the Nova II post is what they called for for my 260 I guess they could be wrong as I see there are many variations and v6-v8 covers a lot of territory. Some people are sure quick to tell you what wrong but not so helpful on what is right. I didnt get ay help on the why the square hole is closed and why it is open in some applications and if I am asking for too much I am sorry bout that. I see posts here go into such detail about some topics, I thought I might get some great help on my problem. There was no thermostat in the engine and the gaskets just look like regular car stuff( the previous wner couldn't figure it out either I guess) so I have nothing to go by and the set of gaskets are deliema. If I block the square hole is it going to mess it up or if i use the square hole open will that mess it up or make it run poorly I could try one and then the other but was hoping someone could save me some time and effort.

 

[tommays]

Re: thermostat puzzel

IF you put in your serial # don can tell exactly what you have AND WHAT YOU NEED


Tommays

 

[Nova II 260]

Re: thermostat puzzel

Mark, did you get your thermostat squared away?
I too was wondering about the blocked port.
I have no temp reading on either guage (dual eng)
sorry for the late response, been on a caribbean cruiseship