hot water tell tale

[circle hook]

I have a 7.5HP 1984 Mercury and the water comming out the tell tale is scolding hot but pumping a great stream is this ok, it means the impeller is working and pumping but I never seen water that hot in my life time. any reasons why Thanks Bob

 

[circle hook]

Re: hot water tell tale

does this engine have a thermostat that can be cloged

 

[emckelvy]

Re: hot water tell tale

If your motor doesn't have a 'stat, it sounds like you may have circulation problems in the powerhead.

I had a 4.5 hp that acted like yours, had an unusually strong discharge out the telltale but was obviously running too warm. Turned out the water discharge passages at the bottom of the block were plugged. So, the only place water could get out was the telltale.

I pulled the powerhead for inspection, found the plugged passages in the middle bottom of the block & cleaned them out. The motor ran & cooled normally after that.

It's also possible for silt/trash to build up inside the main water circulating area around the cylinders. I've seen 'em with deposits halfway up the block. You have to pull the cyl block water jacket cover off the back of the block in order to inspect this area. Just watch out for the 1/4" cover bolts, usually they are stuck and require heat/penetrant to release. Very easy to break these bolts.

If you find a bunch of 'trash' in there, scrape/flush it out.

The water jacket cover can be removed without pulling the powerhead, so that'd be the next logical place to look for problems. After that it's time to pull the powerhead for inspection; you'll need a new powerhead base gasket, water tube rubber grommet, & water tube washer.

Note that sometimes water supply problems are caused by a squeezed-shut water tube grommet or washer, so if you can't find any other reason for your cooling issue, you'll want to pull the powerhead for inspection.

BTW the exhaust manifold should run fairly cool, if it's hot there's definitely a problem.

Hopefully you do have a 'stat and it's causing the problem. If that's not it, time to break out the wrenches!

HTH...........ed

 

[circle hook]

Re: hot water tell tale

THANKS ED I guess its time to brake out the wrenchs again Thanks Bob

 

[circle hook]

Re: hot water tell tale

Ed well I pulled the side exhaust cover with out braking any of the bolts and found a lot of rust and crud now what is the best way to clean out the block coat hanger & compressed air what did you do Thanks Bob

 

[emckelvy]

Re: hot water tell tale

Bob, if the exhaust manifold was full of trash then I'd bet the big water passage area under the cyl block cover is gonna have a bunch of junk in it too.

So you might try pulling that cover, over the spark plugs, for inspection also.

One thing you can then do is pull the lower unit (if not already removed) and blow compressed air up the water tube. You'll get a pretty good idea where things are free-flowing and where they aren't.

After the air, try flowing water up the tube and this will help flush silt/trash out of the block.

I'd still be concerned about drainage out of the block, and you can't really get at the block discharge passages unless you pull the powerhead. But if you can flush water into the block and observe it draining out the bottom of the main cooling area, you're probably safe to assume water's getting out.

HTH & keep us posted on your progress...........ed