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Still overheating %3cIMG SRC%3d%22httpwwwmarineenginecomdiscusclipartsadgif%22 ALT%3d%22%22 BORDER%3d0%3e

R

rickroot

Contributing Member
"Since this is a new thread, I

"Since this is a new thread, I'll re-mention my specs... 1985 Mercruiser MCM-140 engine with an alpha one (not gen II) stern drive.

Recently replaced the water impeller (everything except the water pump base), and installed a thermostat, which my boat has apparently been doing without for years.

Finally got around to running it tonight (with the water on, of course) and she overheated again.

I got up the temp gauge about 3/4 before shutting her down.

Is there *ANY* way I can really tell if my external water pump is working? I mean, barring anything else, it seems to me like there's almost no way to know what's wrong with your cooling system without taking everything apart.

Maybe the water intake is blocked, or one of the water tubes (before or after the thermostat housing). Maybe the thermostat I installed is bad, or maybe the water circulation pump on the engine is bad.

I'm about ready to give up on self-servicing becasue we're approacing full blown boating season and I wanna be out there!"
 
Rick:

You have to give the

Rick:

You have to give the new T'stat a chance to reach its open temp. I just replaced the entire T'stat hsg. and T'stat. When the engine is cold my temp gauge rises up to nearly 225 F. and all of a sudden the temp falls to 143 F. as the new T'stat opens and it stays there all day while running. Turn it off and let it cool off a little and the same story repeats itself. I checked the entire cooling system w/a laser temp. gun and nothing is running hot; all is rather cool.

Let the engine start to get hot and shut it off. Wait a few mins. and turn it on to see if the gauge changes. Did you check the T'stat in a pot of hot water using a string?
 
"Well my engine was definately

"Well my engine was definately hot. Like I said I ran for 5 minutes or so (maybe 10) and got the guage up about 3/4 (ie, over 200 degrees). When I shut it off, the engine was VERY VERY hot.

I'll try running it again now (it's cooled off some) and see how it reacts.

I didn't test the termostat in a pot of water, I'll try that."
 
"I took off the thermostat hou

"I took off the thermostat housing and the thermostat was open - at least partially. The engine temp still read something like 150 or 160.

The thermostat housing looked dry as a bone but at the temp the engine was at I suspect any water that might've been in there, if any, evaporated away.

If I were to run the engine for a few seconds with the water on and the thermostat housing off.. should I expect A> nothing or B> water to squirt out of the open thermostat housing?"
 
"Remove the drive,insert a was

"Remove the drive,insert a washing machine hose cut in half into the inlet.
could the waterpocket be destroved from a overheat
151537.jpg
"
 
"[url=""]http://www.outdrives.

"http://www.outdrives.com/merc/mdtips04.html

------------------------
Now is a good time to look things over.
Look down in the water intake passage and make sure it's clean.
Next, flip the upper driveshaft housing upside down and inspect the copper tube and wear it seats.
The copper tube seats up in the "water pocket cover" which has 4 bolts.
If the water pocket cover looks melted then it should be checked for leaks!

Replacing the water pocket cover sucks BIG TIME because sometimes the bolts snap off
in the upper housing. If they snap off.... you will need a new upper housing!!!
---------------------------

THAT water pocket?

Okay, so when yo"
 
""Remove the drive"

""Remove the drive"

The whole thing, upper and lower? Or just the lower?

",insert a washing machine hose cut in half into the inlet. "

The copper tube going up into the upper unit?

"could the waterpocket be destroved from a overheat "

How would I know? What would happen?"
 
"There are a few things to try

"There are a few things to try, but you might get wet or pump some water into the boat.

1. Run a compression check on your cylinders as you could be fighting a blown head gasket.

2. You could pull the lower unit and use an electric motor (drill?) to run the drive shalf while lower end submersed in water - to see if water pumps out the lower water pump.

3. Make sure the small feed tube is correctly in place on top of the water pump and is connected properly to the water feed line. You would check this as you pull the lower unit and again as you replace it.
4. Disconnect the inlet feed hose to the recirculating pump, and use a garden hose to feed water from the rear (still with lower unit off) to see if water is coming up thru the feed hoses without restriction. If you suspect restriction, revese feed and backflush for effect.

5. Test the thermostat in a pan of water on the kitchen stove to see what temperature it reaches before opening. It should start opening slow as water gets hotter and be fully open by time temp reaches approximately 150 degrees. These are imperfect devices so don't expect an exact 142 degrees to be the magic number.

6. If everything above seems okay, feed the garden hose water to the inlet of the recirculating pump (lower unit still off). You might need to hold/stuff this with a rag or something as someone else starts engine and watches temp guage. This is to check to see if engine runs cool when you KNOW it has water available.

7. Replace the recirculating pump if it appears no circulation within the engine is allowing cooling to occur.
-----------------------------
Likely several other thing to examine, but my mind is not well in gear tonight. Engines do not run hot without a cause. I was trying to come up with DIY tseting you could do, short of parking boat in the sunshine on the dealer's lot for a few weeks awaiting you turn."
 
"You remove the whole drive, i

"You remove the whole drive, insert hose into water inlet hole in gimbal housing
for the water pocket, just need to look.
the one in the pic was leaking the water before it got to the engine"
 
"It` been done before,ask me h

"It` been done before,ask me how i know.
Did you remember to install the keyway for the impeller?"
 
Bt. Dr.:

Are you saying the

Bt. Dr.:

Are you saying the water pocket is in the upper hsg. of the OD where the copper tube inserts?
 
"Saturday morning I'm gonn

"Saturday morning I'm gonna take it over to my sister's boyfriends shop.. he owns an auto shop and is a boat enthusiast. We'll do the compression test and go from there.

Given that I topped out the temp gauge a few weeks ago without noticing until we'd stopped to check something out... seems like that might be an issue.

And luckily, he's willing to do the work for me if it needs replacing. I'm building his auto shop a web site =)"
 
Remember when i mentioned that

Remember when i mentioned that the water tube guide coming out of the old water pump housing was melted? Seems like if that was melted there's probably a good chance I've got issues with the water pocket as well. Of course I didn't even know there was a water pocket a few hours ago!
 
"Rick;
There is a simple test

"Rick;
There is a simple test you can do to see if you have water pumping.

Pull the water inlet hose off the T'stat housing, and while idleing the engine briefly hold the hose in a bucket. You should half fill the bucket in 20 seconds or so. If not, or if no water pumps at all, then you have a pump or hose issue, or water pocket issue as above.

While you have the water hose off, you could try to push water back thru the hose to the drive with a garden hose. This will show you where the water is going.

You will immediately see if the drive leg to transom plate hose is shot. If it floods out of the prop then you know it is leaking somewhere in the cavity between the upper and lower gear cases. That would indicate pump or water pocket.

This will narrow the search down quite a bit for you.

Rod"
 
"Water Pocket:

I understand

"Water Pocket:

I understand now; just never worked on the upper OD before. I probably will be looking at it during the next impeller change since during the last change I observed the copper tube seal did not look very good but the C. tube did fit snug. Good fishing.
rain.gif
for the next few days here. But, I have about 5 lbs. of walleye and crappie fillets in the freezer for a fish fry. MMMMMMMMMMMMM!!!!
sun.gif
"
 
"Rod, I did take the thermosta

"Rod, I did take the thermostat housing off and started the engine for a short bit. No water at all was pumped, so I'll try your suggestion of pushing water back through the inlet hose with a garden hose and see where it comes out =)

And I should be able to do that without taking the stern drive off. I've never take tne whole thing off - just the stern drive - and I don't really have a a good "stand" for working on the lower unit so I've always done it at my dad's house.

IF the water floods out the prop, I might then drain the oil and take the lower unit off and investigate the water pocket cover."
 
"Rick;
Not to belabor the poi

"Rick;
Not to belabor the point, but by removing the drive leg, I only mean the upper and lower gearcase assembly removal (as a unit) from the bellhousing-gimbal assembly. Nothing more.

That is usually easy to do with no special tools, and all you need to work on the drive leg once out is a bench vise to hold it by the skeg.

Just for the record, I've never heard of a disintegrated water pocket either. But with boats I have learned that anything that can possibly go wrong should not be overlooked.

Another thought; Do not take this the wrong way, but are you absolutely sure your drive is working as it should? I ask this because if the vertical shaft in the drive is not rotating, the pump will not be pumping of course. Try putting it in fwd gear and make sure there is no way you can turn the prop CCW by hand. (If the coupler has failed, or the Ujoints or upper gears are toast, the shaft won't be turning.)

Let us now what you find, as we are all curious as hell.

Rod"
 
""Another thought; Do not

""Another thought; Do not take this the wrong way, but are you absolutely sure your drive is working as it should? I ask this because if the vertical shaft in the drive is not rotating, the pump will not be pumping of course. Try putting it in fwd gear and make sure there is no way you can turn the prop CCW by hand. (If the coupler has failed, or the Ujoints or upper gears are toast, the shaft won't be turning.) "

Hah. I did that before even attempting to start the boat. I also put it into gear a bit while running the engine and checked reverse as well... the prop turned (in the correct direction both times!) so I'm pretty sure the drive shaft is turning as it should =)

there are many things I'd rather have than a blown head gasket, so if "water pocket cover" or water tube between engine and upper unit are possibilities I'm certainly going to check them!

I'm afraid if I have a blown head gasket I might need to mooch a lot of time off my sister's mechanic bf =)"
 
"a blown head gasket wouldnt s

"a blown head gasket wouldnt stop the water flow.
pull the drive and hose test. narrow it down to drive or engine.
You could have old sections of impeller blocking the flow completely.
Here`s what happens when the oil gets low.
151583.jpg
"
 
"Bt Doctor - I've seen you

"Bt Doctor - I've seen you say pull the drive several times. I get it. If I have to do so, I'll do that this weekend.

In the meantime... I disconnected the thermostat housing cover (that has the smaller rubber water tube going into it *AND* I removed the larger water tube that goes into the base of the thermostat housing.

Using a garden house, I injected water into the larger water tube. After a bit of water, the tube filled up and water started flowing out of the thermostat housing.

NO WATER CAME OUT OF THE STERN DRIVE UNIT. No water came out anywhere except out of the thermostat housing. Basically, I filled up the cooling system with water.

I decided to try the other house (the one with the thermostat housing cover still attached to it). Ran water into it until it was "full". No water emptied out of the engine or stern drive from anywhere.

About 2 hours have gone by since I did this. STILL no sign of water dripping out anywhere. The water is still in there.

So what the heck? That would certainly seem to imply that the water line is clogged up SOMEWHERE.

That would certainly seem to explain why the water isn't flowing from the lower unit into the engine wouldn't it?"
 
"Rick;
Its hard to know what

"Rick;
Its hard to know what hose you have without pictures, but it sounds like the right one.
Just to be sure, if you trace this hose back, does it wind up back at the transom assembly?
If so, then that is the one.

If you have a camera, send me a pic or two offline and I'll give you my opinion.
Conversely I can send you a pic of a 4.3 assembly; which is not the same, but it will show you which hose to backflush.

If there is no flow thru that hose, you have found your problem. Next, I would disconnect it from the transom assembly and repeat the test. That will tell you if its in the hose or back in the drive leg.

Rod"
 
"See if i have it right.
you

"See if i have it right.
you removed the large hose from the therm. housing and filled the block with water untill it came out the therm housing.
If so, you filled the block.
Then you put the hose in the manifold and "filled it" Well, you shouldnt have been able to fill it because it should run out the riser and out the exaust.The manifold or riser may be completely clogged shut.go back to that little hose and try to blow air thru it or clamp the garden hose to it and see if water comes out the exaust."
 
"The two hoses I'm referri

"The two hoses I'm referring to are #43 and #45 in that picture.

Rod mentioned the inlet hose, which is #29 in that picture I think.

I'll look for that tonight."
 
"Alright so I checked out the

"Alright so I checked out the cooling system section of the merc manual #13

http://www.boatfix.com/merc/Servmanl/13/13A6R2.PDF

The cooling system flow diagram is on the last page. I see that since I ran water into the large host that goes into the engine circulation pump that it WOULD come out the thermostat housing, as Bt Doctor said. And that's what happened.

I also ran water into the exhaust manifold through the thermostat cover assembly. It seems to me like the water would only flow OUT that way "under pressure".. ie when the engine is running, because otherwise when you filled it up with antifreeze for winterization, it would just flow right out, wouldn't it?

So what Rod actually suggested was that I run water into the inlet house, which I didn't even notice when I was doing this last night.

so as I mentioned, I'll check that out tonight.

I wonder if something just got disconnected for winterization, or plugged or something. I didn't winterize it, the boat shop did."
 
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