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1990 57 water pressure

S

srdancer90

Regular Contributor
"Guy, or Bondo, I need your he

"Guy, or Bondo, I need your help, No one knows this, I cantacted Mercruiser directly and they didn't know the answer. Does any one know what the max water pressure is that is delivered by an alpha 1 gen 1 water pump, or what the pressure should be under way. This info is available via outboards ( 12 - 15 psi) not stern drives. I am interested in placing water pressure gauges on my engines. T 1990 5.7's I may have a water delivary problem."
 
Joe;
I seem to remember readi

Joe;
I seem to remember reading that an Alpha Gen II should deliver about 10 psig minimum pressure at mid rpm range.
If you check PC Performance site I think that Hardin makes a water pressure gauge for I/O's that has a range up to about 25 psig.

Rod
 
"Joe:

Sorry, I don't kn

"Joe:

Sorry, I don't know the answer. I can't believe that a merc. engineer would not have the answer. Perhaps the person on the phone was too lazy to get the info. or was not permitted to give it to you."
 
"The Merc tech only knew the r

"The Merc tech only knew the rate of flow per hour, not the psi. Some of the newer merc engines have a provision near the oil sender that allows you to place a water pressure gauge on that engine. The only thing I need to know is the normal range that would indicate a proper flow being delivered to the T stat, for an alpha 1 gen 1 drive.Rod stated that the gen II should deliver about 10 psi,I am guessing that if the lower is simular to an outboard then the operationg range should be about the same. No data avaiulable on this issue."
 
"Joe;
I can't see it bein

"Joe;
I can't see it being over say 15 psig, as that is about as high as a car closed cooling system runs.
High pressure is not necessary; adequate volume is important at a high enough pressure to overcome the losses in the system.
I would think you could try a 30 psi gauge and that should do it.
Let us know what you find out.

Rod"
 
"I believe that it is a water

"I believe that it is a water delivary problem, the symptoms that occur are the engine warms up I run the engine under a load 3500 RPM the temp hits about 150-155, then the gauge drops to 0, then returns to 145.If it stays at 0 for a period then the engine is brought to idle range, the gauge will hit near the 200 degree mark, If this happens I place the engine in neutral, then rev it and the water temp will drop to the 145 mark.I ran an independent wire from the sending unit to the gauge and it responded in the same fasion,so I believe this is not an electrical problem. (I did not remove the ground wire from the gauge when I ran the independent lead.) I removed the sending unit, replaced it with another, it did the same thing. The water pump in the drive was completly changed in the winter as well as the the water pocket assembly,The hose in the bell housing was done in the spring. The circ pump was done 2 years ago as well as the risers and the manifolds. The reason for the water pressure gauge is to determine if there is ample pressure, meaning a good flow to the T stat.(I am not sure if good water pressure 15 psi implys a good volume being delivered.)
Some Merc tech told me to try a clear hose from the T stat to the risers and look for the flow, if there was air there I am not sure what that means, maybe a bad T stat housing ( not changed.) I am at a loss. nees suggestions."
 
"Joe:

Is this what your T&#

"Joe:

Is this what your T'stat hsg. looks like?

http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=816596&ivar=images/CRUISE R/816596/22.png&inbr=1014&bnbr=230&bdesc=STANDARD+COOLING+SYSTEM+%28DESIGN+III+% 2D+ALPHA%29

It could have alot of rust buildup in the passages restricting flow. The temp gauge reading one minute and not the next says not enough water is getting into the block for cooling.

Hook up a clear hose from the T'stat hsg. to the OD connection. Run the engine and look for bubbles in the hose. The OD may be sucking air w/the water from the impeller; not enough flow. Water pocket may be the problem."
 
"A pressure gauge might just m

"A pressure gauge might just make it more confusing. If the risers are half plugged and the impeller is half good, you will read proper pressure even though you have 2 serious problems. The Merc engineer can't tell you the pressure the pump delivers, because pumps don't deliver pressure. They simply move water and the restriction to flow is what causes pressure in the system. Although I'm surprised he didn't have some "typical" numbers. A flow meter would be a useful diagnostic item."
 
"I found the problem, I had a

"I found the problem, I had a merc tech run the boat. He attached a clear plastic hose and found air in the water delivary. I thought that I solved the problem, By changing the hose in the bell housing, apparently I did not solve the air issue. My confusion lies in that I changed the lower base assembly, the impeller (every season end.) and the water pocket assembly. I seems that none of the measures has solved the air issue. When the boat ran he said it was 75% water and 25% air. So, the engine thermostat reads air and the gauge drops to 100 degrees, when the temp in the engine reaches 180 by steam the thermostat opens and the engine cools down, the gauge rises to the 145 mark (from 190) He suggested that (and I never heard of this) I drill two(2) 1/8 inch holes into the thermostat flange to relieve the air and allow the engine to run at 145. This is a temp measure and I need to look at the drive and determine where the problem lies. Apparently it may be a casing issue. I am not so sure that I know what I am looking at in the drive. But it seems that exhaust gases are being mixed with the water that the pump is delivering."
 
"When you changed the water pu

"When you changed the water pump base did you install the gasket properly, it can be reversed.
Use contact cement,bellows adhesive on the gasket in the area of the water flow. you could be sucking hot gas .a bad gasket seal or warped base will allow hot exaust gas to enter the pump base.
216508.jpg
"
 
"The merc tech did the waterr

"The merc tech did the waterr pump assembly. I purchased a sierra water pump kit. I believe that the water pump gasket is correctly installed. If it were reversed, would it not allow water to enter the engine? He used hytac ( spray )to the lower gasket when it was assembled.If I change the assembly again, can I check to see if there is air introduced when the drive is on a garden hose. It seems that there is air at idle it is there as well as under way. I am assuming if it shows at idle then it shows under a load, if it does not show at idle, can I assume that it will not show under a load. I can rev the engine for a little while on the garden hose up to 2500 rpm for a second or two. My other question is can I use bellows adhesive around the sides of the water pump base as well as on the gaskets install it into the well of the housing and eliminate any gasses that are introduced this way? Whats the oponion on this. My other choice is to install a thru hull pick up and a raw water pump."
 
"Joe;
Something sounds wrong

"Joe;
Something sounds wrong here.
The water pump normally runs below water level, so the water wants flow into the pump. This is called a "flooded suction", in pump engineering terms.

The only way air could be drawn into the pump is if the pump case is cracked, or the lower gasket is leaking, in the front half of the pump. But as long as the suction is flooded (ie positive pressure), there is no way it will want to pull in air or exhaust gases. From the outlet nipple of the pump on through the rest of your cooling system the pressure is positive, so there is no way air will be drawn in anywhere else.

Are you sure you are using enough water flow on the muffs? YOu should see surplus water spraying out the sides of the muffs as it is running. If not, you have insufficient water, and you could be sucking air into the pump (since on the muffs you do not have a flooded suction technically).

Do not worry about what you may have read about excess water pressure on the muffs possibly causing damage. That is a load of crap.
The spring style muffs are pressure regulating by their design, and there is no way you can damage anything by cranking up the water. You will do much more harm if you have insufficient water.

Rod"
 
""drill two(2) 1/8

""drill two(2) 1/8 inch holes into the thermostat flange"

I've seen this in a book somewhere.

Rod:

"...through the rest of your cooling system the pressure is positive, so there is no way air will be drawn in anywhere else."

I'll argue that point. A pressure washer uses siphoning action to pull soap into the flow of water from the positive pressure created by the pump. If the soap tank runs dry then it is sucking air.
uhoh.gif
Right or wrong?

I think there is a crack or weak seal somewhere between the OD water outlet to the engine and the impeller."
 
"When I split the drive over t

"When I split the drive over the winter I did not notice any cracks on the wall that exhaust gasses pass by. In fact I did not notice any visible cracks in the lower interior portion of the drive.If we use BT's photo of the base assembly, the lower gasket would be the one that is facing the exhaust passage of the drive? Would it be correct to say that there is positive pressure from the top of the impeller up towards the bell housing? so the only way that exhaust gasses are entering the system are from below the upper water pump assembly cap? I would thing if the lower base of the waterrt pump is cracked then there would be water showing in the oil, and in my case the oil is true blue/green in color."
 
"Guy;
I'll agree with you

"Guy;
I'll agree with your pressure washer point, but the reason it sucks soap or air is that there is a venturi system that produces a negative pressure where the water flows through a restriction.

The same is true of a weed killer or fertilizer attachment that you put on the end of a garden hose. The chemical is sucked up and mixed into the water stream by the negative pressure formed in the venturi mixer.

There is no part of a marine cooling system that I know of that is designed to do this, so I don't see how air could be sucked in anywhere except right at the pump (the only place the pressure is lower than atmospheric), and then only if the suction is not fully flooded.

Anyplace after the pump the pressure is higher than atmospheric, and if there is a leak, water will leak out; air will not leak in.

That's my take for what its worth.

Rod"
 
"Well said Rod.

My carb flo

"Well said Rod.

My carb flooded at the ramp. I caught a 60 lb. Weimeraner (bird dog thought the lure was a bird) in the lip on my first cast. It cost me $95 to have the hook barb removed. Soooooo, the trip was a flop. But I got the carb rebuilt the next day and it runs better than ever."
 
Joe:

To rule out exhaust ga

Joe:

To rule out exhaust gases entering the cooling system borrow an analyzer and loosen a drain plug on the block to get a water sample.
 
"Guy;
I am sure at the time i

"Guy;
I am sure at the time it was not funny, but too bad you did not get that first cast on video to send to Funniest Home Videos. It would be a sure winner.

I saw from your other post that the carb issue seems to be resolved. That is great news. glad to hear it worked out.

rod"
 
Joe:

Go to AutoZone or Adva

Joe:

Go to AutoZone or Advance Auto PArts; they should have one to use for free.
 
"Is it possible that there is

"Is it possible that there is not enough water exiting exiting through the Y pipe so that hot gasses will cause damage to the water pump assembly,cause it to warp, alowing air to enter from the exhaust. Sometimes when the boat runs at the dock I hear a swirling sound. The reason that I ask is I did not see any cracks in the lower housing when I did the pump in the winter.( eithor did the merc tech.) My next thought is can I inject a dye through the riser and watch the incoming water from the oil cooler to see if it is being drawn through the water pump."
 
"Joe;
If you are getting adeq

"Joe;
If you are getting adequate and typical water flow to the risers and into the exhaust, you should be able to comfortably touch the down-elbows that attach to the Y pipe. If they are too hot to touch you have insufficient cooling water.
Again, you have either inadequate pump volume, or a restriction in your system.

The dye idea should work. You could T into the water line to either riser, or both.

I really think that before doing any of this or drilling releif holes in the stat housing, I would pull the drive and recheck the whole water pump, as this is about the only area where air can be getting into it.

I'll repeat this from an earlier post:
"Are you sure you are using enough water flow on the muffs? YOu should see surplus water spraying out the sides of the muffs as it is running. If not, you have insufficient water, and you could be sucking air into the pump (since on the muffs you do not have a flooded suction technically).

Do not worry about what you may have read about excess water pressure on the muffs possibly causing damage. That is a load of crap.
The spring style muffs are pressure regulating by their design, and there is no way you can damage anything by cranking up the water. You will do much more harm if you have insufficient water."

Rod"
 
"The water pocket assembly is

"The water pocket assembly is new, the boat at this time is in the marina, the merc tech who took a test drive with me said that the temp from the laser gun read 125 at the thermostat, 135-140 at the top of the risers yet 155 + on the exhaust side of the starboard riser. We ran the boat with a clear hose and there was apparent air in the line. I have to short haul the boat and split the drive. I did open the two drain plugs and a lot of rust type of material exited the engine, and it did run a little cooler after I drained the block. Can you use a garden hose and attach it to the bottom side of the exhaust manifold and run water up into it with out doing damage to the engine? If this can be done I will try to flush out any other stuff that may be causing the flow restriction. Another tech said it the lower exhaust baffle plae may be rusted away and that is why I am getting air into the T stat. I did not notice any part of the exhaust area rusted away. But the only way I am going to determine this is to split the drive. Getting the wrenches as we speak."
 
"Joe;
That is most definitely

"Joe;
That is most definitely an alpha Gen II water pump.
As we said before, if the pump suction pulls a vaccuum and there is a way for air to get in, it will pull in air. This article is your proof that this does actually happen, in black and white (actually blue on black).

What I don't get is if the pump is submerged and water wants to flow into it, how does it preferentially pull air?
It makes me think that the crescent shaped water inlet in the base plate is not big enough to allow water in fast enough, and the pump pulls a partial vacuum. Do any of the vets on the forum know if the Gen II baseplate intake slot is smaller than the older Alpha and pre-Alpha?

This article makes a great case for the transparent hose test; or a water flow test into a bucket. If there was air in the flowing water you would surely see it coming out with the water into the bucket, in the form of lots of small bubbles.

For you Joe I think the answer is clear; you have a pump air leak somewhere.

Rod"
 
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