Water Intake... STUMPED

[imported_TheMan]

Mercruiser 3.0 with Alpha One.

I replaced the gaskets, o-ring, and impeller of the sterndrive water pump. I've made sure all the lines are clean. This was all after I identified the impeller as being bad as no water was coming up to the engine. (The old impeller was toasted.)

With water supplied to the sterndrive by muffs, the system still isn't pumping water up to the engine. I have taken it apart again and double checked to make sure it is installed correctly. I couldn't find anything wrong and reinstalled the lower unit. Still no water.

I'm looking for any assistance you guys may have from either your own experiences or just your expertise. Thanks!

SB

 

[mkpj1]

Re: Water Intake... STUMPED

Hey Man,

I start off by saying i know know "jack" about Merc's but I restored a 67 "rude" OB that it was absolutely imperrative it didn't run dry. the impellar would shred into the pipes and melt clogging the system. Bad news. The OB system was pretty easy to isolate and you could use compressed air to figure where a clog may be. Still a lot of busy work. I hope someone here can give you a better scenario. Don S. has a PDF Merc Manual that is extremely helpful. I happened upon a Clymer manual with my latest "Merc" endeaver which he has not so many good things to say about?? Probably would give the water jacket schematic?

 

[flashback]

Re: Water Intake... STUMPED

mkpi1 has a good point.. when you say your old impeller was "toast" what did you mean? If a blade or two is missing on the old one, it has no doubt traveled up into the cooling system.. I would look for it somewhere around the steering cooler or thermostat..

 

[imported_rosco]

Re: Water Intake... STUMPED

dude, pull the out flow hose off and crank it and see if it is pumping out water.

if it isnt, its the impeller or blockage in the pick up.

if it is, its probably your thermostat. if you havent rreplaced it in the last 2 years, its probably toast as well.

 

[imported_TheMan]

Re: Water Intake... STUMPED

Maybe I didn't make myself quite clear.. The lines are open.
I have the water intake hose removed at the thermostat and crank the engine to see if water is propelled up the hose. No water is coming out of the hose, as I would assume there should be.
I have injected water both ways through this hose from the engine side and the lower unit side. There is no blockage and the hose is not clogged.

The pickups are clear. You can clearly see the intakes from inside the lower unit and there is no blockage.

The impeller is brand new. The gaskets are brand new. For some reason, the water is not being pushed from the impeller up to the engine.

I have a service manual and I have the clymer manual. The problem is not an obvious one. It doesn't make any sense, which is why I am stumped. The shaft turns, the impeller is new, the lines are clear. But there is no water going to the engine. That is why I was asking for experience or expertise that has seen a problem like this before. I wonder whether my muffs simply do not provide enough water pressure, or seal well enough, to reach the impeller.

Please, no more replies on maybe the lines are clogged.

 

[mkpj1]

Re: Water Intake... STUMPED

Sorry my fault, It's right there in the second line.

In my experience if no one with "experience" does chime in and it's not obvious,....then it's something right in front of my face. Go have a beer, watch a game, whatever.....let it ride for a while? In my case, it's usually something I laugh about later.

Good Luck

 

[imported_rosco]

Re: Water Intake... STUMPED

ok, the hose at the thermostat should be where the water leaves your block, then goes into the exhaust.

if the thermostat is stuck, nothing is going to come out.

pull the thermostat. theh crank the motor and see of water comes out of the thermostat housing with it out.

there are only 3 places that will stop the water from flowing. even if a piece of the impeller breaks off, it "might" block a head water jacket, but most likely, be pushed into the block and sit harmlessly. it could, however, block the outdrive but you say you can pump water through it and it is ok.

1. the raw water impeller. its new, so its not that.
2. the thermostat. if its closed or blocked, nothing is going to get passed it.
3. the water pump on the motor itself. i have seen boats where the metal impeller was corroded completly off. that would do it too, but it wouldnt stop the flow of water, only slow it down significantly.

its either blockage in the outdrive pick up, the thermostat, or the water pump on the engine. thats all there is to the water system on a inboard once you have eliminated the raw water impeller. there simply is nothing left but water passages in the cat iron, and the only place that could possibly stop all water is the water pump on the engine, the thermostat, or the raw water pump and or pick up.

 

[imported_TheMan]

Re: Water Intake... STUMPED

There are three hoses at the thermostat housing. One is the intake from the stern drive. One is to the exhaust manifold, and one is to the engine water pump. The water pump also circulates the water back to this point.

The hose that I am speaking about and have disconnected is the intake from the stern drive. My problem is not thermostat related, nor engine water pump related. It is isolated to the stern drive intake system.

Once again, this is why I am stumped. The system is relatively simple, and should be fine. But it isn't. I'm thinking there is some minor problem which is causing the pump to not work properly.

Mkpj1, I actually developed the problem yesterday and did have several beers to brew it over.. Unfortunately, I am still stymied, even after tearing it apart again today. Got some family coming to visit and was hoping to take them out on the boat, but with my current situation it's not looking good.

I'm gonna tear it apart one more time and make absolutely sure that I didn't do something stupid (I would have had to do it twice) like misplace a gasket. I just thought I would check to see if anyone had any unusual experiences such as this. For once I am hoping that I am just stupid :d

 

[Don S]

Re: Water Intake... STUMPED

What year is your 3.0L Alpha I ?

Did you use new gaskets above and below the SS plate between the upper and lower housings of the pump when you changed the impeller?

 

[johnbo]

Re: Water Intake... STUMPED

One thing you might try is to look for a air leak. Maybe pressurizing/capping the endpoints and seeing if the air is escaping. I've also heard of replacing the intake line from the transom up to power steering oil cooler with a clear line to see if there are bubbles.

It wouldn't take much of a air leak to defeat the suction of the intake pump.

My two bits...good luck,

johnbo

 

[ziggy]

Re: Water Intake... STUMPED

ya say ya have taken it apart a few times. any chance ya missed gettin the water tube between the upper and the lower to mate proper? or maybe a leaky water pocket cover i think it's called. the part on the upper that the water tube goes into...maybe. just tossin out some ideas.....

 

[Don S]

Re: Water Intake... STUMPED

John, your Volvo is different from his Mercruiser. The raw water pump on any alpha drive is in the outdrive itself. No way to put a clear hose on the suction line like you can a Volvo. Also on the Volvo's or even Mercruisers with engine mounted pumps, you have to have the boat in the water for the test, not on muffs. They always suck air and water and would be a non test.

 

[johnbo]

Re: Water Intake... STUMPED

Thanks Don. The Volvo is my first boat and I had forgotten about this difference. My mistake (won't be the last I'm afraid).

Later,

johnbo

 

[imported_TheMan]

Re: Water Intake... STUMPED

Hey Don, Thanks for trying to help. It's a 1989 Alpha one. I replaced the gaskets on the underside of the waterpump base, on top of the base, the plate itself, the gasket on top of the plate, the impeller, the water seal on the shaft, and the shaft o-ring.
I'm just about positive (I will take it off and look at it one one more time) that I followed the service manual diagram to a T.

Ziggy, I have been careful to make sure I align the plastic tube from the pump with the water tube from the upper part of the unit. I am not sure about the water pocket cover you mentioned. I may pull it out and take a look to see if anything is visually wrong. I know the tube is inserted into the cover, but thats about it at this point.

While I have probably poisoned myself in some way or another, I have tried sucking through the intake hose at the thermostat housing with the engine running to see if I can get any water to come up. I can't get any water, but the hose isn't under a vacuum condition, I just get air. I don't know if this would suggest anything or not. Since the hose should ultimately run straight down to the impeller (with a few connections and adapters), if I'm not mistaken, it would seem that theres no water at the impeller. Otherwise I have a broken connection somewhere in the upper gear housing, which I'm not familiar with yet. I don't believe that this is the case because if I send water down the hose, it comes out at the sterndrive intake.

I don't understand how the impeller could not be getting water though as I have the muffs seated on there as well as I possibly can. And again, nothing is blocked.

 

[imported_TheMan]

Re: Water Intake... STUMPED

When I get home from work today I am gonna pull the lower unit and make sure my muffs are getting enough water up to the impeller.

 

[ziggy]

Re: Water Intake... STUMPED

I may pull it out and take a look to see if anything is visually wrong

be carfull inspectin that waterpocket cover. them bolts snap off real easy. i discovered a leak on mine and just had to break off 3 of the 4 SS 1/4 20 bolts in the aluminum upper. you'll be lucky to save the upper if ya break the bolts off. i found my leak at the water pocket cover by runnin water from the hose that connects to the t-stat houseing back out the drive with the lower off. ya could see the water comeing out the gasket along with out the hole where the tube fits in.

another thought. did ya use a torque wrench on the impeller houseing cover. they don't take much torque and there are 3 different torque values for them bolts i think, all in inch lbs. perhaps ya over torqued the bolts and distorted the cover........

 

[freddyray21]

Re: Water Intake... STUMPED

my only suggestion is check below the impeller. If you sucked something into the intake the impeller could be brand new, but not getting any water to it.

 

[imported_TheMan]

Re: Water Intake... STUMPED

Ziggy, I'll try sending water down with the lower unit off. And be careful if I decide to remove the cover.

I moved not too long ago and don't have all my tools down here yet, including a torque wrench. I read the torque values before hand and believe I have them pretty close. (25-30 in-lbs for the back and 35-40 for the front I believe). I'm a little confused on how the pump would be negatively effected even if I did overtorque them? I could understand if the cover was so distorted as to not seal properly, but what else would it cause?

The pump cover sounds more and more suspect as I think about it... Should have thought to check it before. Thanks though.

P.S. Whats happening to those Huskers? Not that my team (MSU) is on the right track....

 

[sumcat1]

Re: Water Intake... STUMPED

Is the impeller turning? I'm not familiar with the I/O impeller but I once had an almost new OB impeller where the rubber was not bonded well to the core that turns it.

 

[mkpj1]

Re: Water Intake... STUMPED

Again from OB experience as I won't change my first Merc Impellar until Spring....I had a weak key that would let the impellar slip? Kind of like Sumcat. since you already fried the first impellar and the pickup is clear, gaskets are new, shaft is turning? what's left? key and housing. Seems housing would be weird as with an OB you really haveto work with some oil and truning the shaft to get the impellar to seat correctly. It would have to be a lot of distortion. That's why I needed a better key in my situation.


Keep us up to date. I had a couple of beers for you to last night too. I told my wife it was a Man Rule and I was obligated to make the boat Gods happy