Water inlet line pulling a vacuum

[Muqwump]

69 MERCRUISER 165 I/L 6. I think i found the problem on the over heating but need confirmation. After changing out the pump in the lower unit, my engine was running really hot. I pulled the water inlet line and found that it had a vacuum while running. How could the pump be running backwards to pull a vacuum? I did rotate the shaft while installing to get the veins going in the right direction but i was also told that they would self align once installed.

 

[Uraijit]

Re: Water inlet line pulling a vacuum

The inlet SHOULD have a vacuum. That's how it draws water.

 

[Muqwump]

Re: Water inlet line pulling a vacuum

Im lost then, When the water is picked up from the out drive pump, where does it go from there? I thought it came up from there to the water inlet line to the thermostat housing. This is a early model 1 drive.

 

[Muqwump]

Re: Water inlet line pulling a vacuum

I took the line off at the t-house and took a water hose and shot water down it. The water comes out where the muffs go. This is the same line that pulls the vacuum.

 

[Don S]

Re: Water inlet line pulling a vacuum

I have to assume the "Inlet" line you are talking about is the hose that goes from the transom shield to the thermostat housing, and that if you disconnected that hose at the thermostat housing, there is just a slight vacuum on that hose and not very much.
If all that is the case, I would suspect the tube from the water pump to the water pocket fitting in the upper isn't in one of them. This would allow the exhaust going out of the drive to actually draw a slight vacuum, similar to a venturi effect.
Kind of hard to explain, but raise the drive and look at that tube and see if its connected.

 

[Muqwump]

Re: Water inlet line pulling a vacuum

I will go raise the drive up and see what i can find. What did you mean by isnt one of them ( Don) ? Also do you know if those veins will self align so i rest a lil easier on that one?

 

[Muqwump]

Re: Water inlet line pulling a vacuum

I raised the drive and everything was in order. There are no restrictions or anything being pinched. So if that 3/4 - 1 inch line does not feed water to the thermostat housing, what does?

 

[Don S]

Re: Water inlet line pulling a vacuum

Pull the drive and make sure the hose from the thermostat housing and the opening in the drive bellhousing are clear.
I would also be taking taking that water pump apart and rechecking everything. If it's been overheated you probably need the lower base and the upper housing. They melt, warp, suck air, and in general don't work.

What did you mean by isnt one of them ( Don) ?

Where did I say that

 

[Muqwump]

Re: Water inlet line pulling a vacuum

I have to assume the "Inlet" line you are talking about is the hose that goes from the transom shield to the thermostat housing, and that if you disconnected that hose at the thermostat housing, there is just a slight vacuum on that hose and not very much.
If all that is the case, I would suspect the tube from the water pump to the water pocket fitting in the upper isn't in one of them. This would allow the exhaust going out of the drive to actually draw a slight vacuum, similar to a venturi effect.
Kind of hard to explain, but raise the drive and look at that tube and see if its connected.

This is what i was refering to.

 

[Don S]

Re: Water inlet line pulling a vacuum

I was referring to the tube was not in one of the items. Either the water pocket or the pump housing.

 

[Muqwump]

Re: Water inlet line pulling a vacuum

I have had everything replaced on the cooling system. Even the bellhousing itself. The only thing i havent replaced is the engine itself. The timing is correct also. This allstarted with a hole in the exaughst manifold last year. I saw it was corruded and unrepairible so i had everything in the entire cooling system replaced. Since then i have taken everything back off piece by piece trying to find anything.

 

[Don S]

Re: Water inlet line pulling a vacuum

what about that tube that goes thru the transom shield. I have found them completely plugged up

 

[Muqwump]

Re: Water inlet line pulling a vacuum

The tube was part of replacing everything in the cooling system. I also checked it by flowing water from the t-housing to check for restrictions or leaks around it. There were no leaks at the transum and water flowed well out of the bottom of the drive. What delivers the water to the engine if this line does not?

 

[Don S]

Re: Water inlet line pulling a vacuum

also checked it by flowing water from the t-housing to check for restrictions or leaks around it. There were no leaks at the transum and water flowed well out of the bottom of the drive.

It shouldn't be flowing that well, the pump should be slowing down or stopping most of the flow.

 

[Muqwump]

Re: Water inlet line pulling a vacuum

With the engine running or not? I am going to pull off the drive again for the 5th time to check the pump again. It is pretty routine now but i may be doing something wrong everytime i do. Any suggestions on what else to look for while Im in there? Could i be installing the veins in the wrong direction? Ill be back in 20 min when i have it off and apart. I am still lost on how the water gets from the outdrive to the t-housing.

 

[Don S]

Re: Water inlet line pulling a vacuum

If you have a new impeller, it makes no difference on the pre Gen II alpha drives which way they go. They will flip over to the right direction.
The pump work by the impeller vanes straightening out while over the intake port of the pump housing, then you have water between the vanes and the exit for the water is blocked from the intake, and starts opening on the oulet port of the pump. The vanes then start squeezing down and push the water out the only place available. The outlet side of the pump. It happens continuously and gives you 3 or more lbs. of water pressure.

 

[Muqwump]

Re: Water inlet line pulling a vacuum

Thanks Don for your help, I took off the lower out drive and the pump looked new still. No wear or damage to it that i can see. I checked the torque when i took the housing back off and it was still the same as it was when i installed it last week. I am going to start all over again with the cooling system. I had the old head rebuilt when i had the exaughst manifold off last year but i am thinking i am just going to replace it now since there may be some kind of blockage in there. Any suggestions or recommendations on buying one? Part number? Then also i am going to rebuilt the outdrive. Do you think this is an achievable home project. And should i do both upper and lower part of the outdrive? When it is engaged fully it has a clunk to it.

Thanks again!

 

[Don S]

Re: Water inlet line pulling a vacuum

If you aren't getting water out of the raw water pump, you can rebuild the engine, manifolds, thermostat housing and everything else all day long and it will not make the pump work.
You have put muffs on the drive, started the engine and didn't get any water out of the hose that goes from the transom shield to the thermostat housing when you remove the hose from the Tstat housing. Why would you now think there is something wrong AFTER that hose. You have no water from the pump. Deal with that problem first.
If you had water to the thermostat housing, then you might have some reson to look for a plug in the engine some where. But you don't have water there.

Do you have an OEM service manual? Or just working by the seat of your pants?

 

[Muqwump]

Re: Water inlet line pulling a vacuum

I do have the Original Mercruiser Service Manual and also the Clymer shop manual. You are right, i am not getting water from the transum to the thermostat. I am getting a strong vacuum when i disconnect it at a idle speed. That is why i am confused where the water that i am getting is comming from, but it is not enough to cool the engine.

 

[Muqwump]

Re: Water inlet line pulling a vacuum

I have it back together with a new kit installed, the housing was replaced last week and the lower plate as well. I put the muffs on and water came out the shift lever. Is this water that is comming out around the bushing on the water tube?