1994 merc 9.9 cooling system on thermostat?

[nine nine man]

I just bought a 1994 9.9 hp merc and I was wondering if the cooling system in this motor is triggered by thermostat? When I have run the motor, the stream coming out the pee hole has been intermittent. on average Id say that it's like 5 seconds on and five seconds off. Sometimes varying to longer intervals. is this normal? how hot (to the touch) should the water coming out be?

 

[o/b tech]

Re: 1994 merc 9.9 cooling system on thermostat?

The thermostat contols the operating temp of the motor untill 1800 rpm and is then pushed away from its seat allowing full water flow. It is normal to see the condition that you described and for the water to be hot to touch after it reaches normal operating temp. There should be a steady stream being discharged when it is throttled up.

 

[nine nine man]

Re: 1994 merc 9.9 cooling system on thermostat?

Thats the problem... it was still intermettent when I was up to speed at 3/4 throttle and up. it seemed as if it was still running from the thermostat. I figure this because the intervals were fairly even. Would this mean that I need to get a new thermostat? or could this even be an intake or impeller problem? .....thanks for the quick reply!

 

[o/b tech]

Re: 1994 merc 9.9 cooling system on thermostat?

It would be good maintenance if you replaced the impeller anyway as you do not know when it was last changed. It is a terminal item and would be a good place to start.

 

[o/b tech]

Re: 1994 merc 9.9 cooling system on thermostat?

When you ran the motor originally, was it in a tank of water or on the muffs or on the water. The static water line can also create the same problem.

 

[nine nine man]

Re: 1994 merc 9.9 cooling system on thermostat?

this was when i was running it out on the water. Whats this static waterline thing?

 

[o/b tech]

Re: 1994 merc 9.9 cooling system on thermostat?

Replace the impeller to start and it gives you the opportunity to see the condition of the old impeller.

 

[o/b tech]

Re: 1994 merc 9.9 cooling system on thermostat?

You may also have a blockage in the in the discharge of the tell-tale fitting. Try pushing a paper-clip into the fitting and see if it changes.

Hope the info helps.

 

[nine nine man]

Re: 1994 merc 9.9 cooling system on thermostat?

it seems to me that the problem would have to be coming from whatever drives the actual impeller to have such even on/off intevals while at speed. ????? please enlighten me!

the tell tale fitting is located at the vary end of the cooling system?

 

[o/b tech]

Re: 1994 merc 9.9 cooling system on thermostat?

The impeller is keyed to the driveshaft and turns continously. The tell-tale fitting is where the water discharges out of the belly-pan.

To also help you along you may want to pick-up a seloc service manual.

 

[emckelvy]

Re: 1994 merc 9.9 cooling system on thermostat?

Take a look at this diagram, which should be close enough to your motor:

http://www.mercruiserparts.com/Show...=497&bnbr=110&bdesc=Cylinder+Block+and+Covers

You'll note where the telltale hose is located in relation to the thermostat. Sounds like the 'stat is doing its thing, except that maybe it's not relieving properly at higher speeds/water pressure.

If you pull the thermostat cover you can inspect the 'stat and even run the motor for a few seconds to see if you get lots of water flow out the open hole.

The springs on your 'stat might have debris/corrosion products built up on them and don't operate correctly, even though the 'stat is opening and closing to regulate temperature.

I don't know why Merc chose to build the telltale that way (probably cheaper) but it's very annoying not to see water flowing as soon as you start the motor! Just the way it is with these.

As the other posters said if you don't know how old the impeller is it's a good idea to replace.

Before looking up part numbers at this site or anywhere else, make sure you have your Serial # handy. They do change things once in a while and it's important to be on the correct diagram for your motor.

Besides a 'stat, you'll need the thermosat gasket and thermostat cover gasket, parts #42, 43, and 40 on the above diagram.

HTH & let us know what that 'stat looks like!............ed