Mystery to be solved - reward to whoever gets it!

[The Hammer]

Re: Mystery to be solved - reward to whoever gets it!

Told my wife to sit in the center of the boat. Got rid of the 30 degree starboard list. Problem solved.

I'm with you, get the mother in law to stand on the starboard side.

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

So, if there are no bubbles comming in from the seawater pump, you are saying I should'nt be seeing any bubbles at all going to the manifolds?
I am wondering how I could be getting this good of an incomming volume of water (4.5qts) every 15 seconds if there was air also being sucked in.
I guess the clear tube will put that question to rest.
Going out to put it on now.
Will report back later.

Kirk

 

[Don S]

Re: Mystery to be solved - reward to whoever gets it!

Just realized something. You have a gen II and getting air bubbles can only come from before the pump. Read this bulletin.

http://www.boatfix.com/merc/Bullet/95/95_13.pdf

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

Thanks Don, that is exactly how I assembled it ...I think I saw this bulletin ...but bottom line is, I guess, there should be no air bubbles anywhere at any time, is this right?
Thanks
Kirk

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

RESULTS:

OK, replaced incomming hose with clear hose, started engine, checked hose,
AIR BUBBLES BIG TIME ... LOTS OF THEM!!! It actually looked like it was about half water and half bubbles ... hose never did have a chance ti completely fill bubble just kept on comming. I assume it isn't supposed to be like that huh?
So it is sucking air somewhere and not getting an adequate amount of water ...but my flow tests showed it was ... maybe it only sucks in bubbles when it is under a load and during the volume test it isn't under any load (pushing load) .....confusing.
Before I change to restrictor gaskets I want to find this leak.
Now I checked again and the water in the tub actually only comes up to the bottom of the cavitation plate but well above the intake screens. So I would think I shouldn't be sucking air since it is all above that.
Now, here is another thing, when I took the hose loose from the tstat housing in preparation to put on the clear hose ... I blew into the hose expecting to hear it bubble up in the tub of water. It didn't I could blow into it and I heard the air escaping somewhere. I then put on the clear hose and did the test.
I suppose the point where I heard air escaping is the point where it is sucking air ...but where could that be? The hose between the bell housing and transom is new.
I guess it could be the O rings on the tube which goes between the pump housing and the upper gearcase or maybe the face seal on top of the pump housing.

I think maybe it is time to pull the drive again and look for this leak.

Anyway I think I am on the right track now.

Thanks ... any other ideas are welcome.

Hope I find something obvious in there.

Kirk

 

[Don S]

Re: Mystery to be solved - reward to whoever gets it!

OK, replaced incomming hose with clear hose, started engine, checked hose,
AIR BUBBLES BIG TIME ... LOTS OF THEM!!!

Please tell me you have it in the water and not on muffs. If you have it on muffs, that test will tell you nothing.

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

In a tub of water ...water is up to the cavitation plate and a hose keeps the tub full when running.
Shouldn't that be the same or does the drive have to be deeper in the water ...like where the pump housing is below the waterline maybe?

 

[Don S]

Re: Mystery to be solved - reward to whoever gets it!

The water has to be over the intakes, not just up to them, but if you are over them, then is should be ok and you shouldn't see bubbles. Since you do, go put it in the water, then the water will be above the pump housing. Then see if you have bubbles. If the bubbles go away, then your pump is leaking where it bolts to the drive, I don't care how well you think you sealed it, it has to be there.

 

[smokeonthewater]

Re: Mystery to be solved - reward to whoever gets it!

KWG glad to see you're back but sorry to hear about your continued trouble.... It can't be sucking air above the pump because that is all pressurized.... any leak would be water out not air in....

The leak has to be in or under the pump..... I still think the gaskets should be changed but obviously the air leak needs fixed too... good luck

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

Don,

Thanks, that makes sense ...what if the bubbles don't go away is it still leaking at that spot?

I have to drive 30 miles to put this thing in the water is the reason I ask so if either way I will have to re-do the pump housing gaskets I will just do that first and see if it cures it here at my garage in the tub.

Kirk

 

[Don S]

Re: Mystery to be solved - reward to whoever gets it!

I can't imagine the bubbles not going away. Everything after the pump as at least 1 psi of pressure on it. So it would leak water externally, not suck air. The ONLY place it can suck air is BEFORE the pump. (aka on the suction side of the pump).

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

So, the bubbles would probably go away. Which means the pump housing is leaking as you say. If the pump housing wasn't leaking then bubbles would have to come up from the tank when I blew into the hose at the tstat fitting..is that right? I could hear air escaping somewhere out the back and no bubbles comming up from the tank when I blew into the hose.
If I had to guess I would say since the pump housing is presently just above the waterline that the air (my breath) is escaping there so it is probably not sealed as you suggest, or maybe one of the O rings in the tube seal or the face seal on the housing. If they all were OK then air should have bubbled up from the tank from the inlet screens.
I will pull the drive tommorrow and triple check all that stuff.

I have a feeling this is where the mystery may end.

Thanks a LOT for all of the help guys.

Keep those fingers crossed for me.

Kirk

 

[cdiamond]

Re: Mystery to be solved - reward to whoever gets it!

I dont know whether you are in a salt water area

But down here in sw fl.
What I have seen many times

Is on the surface of the lower unit housing, where the first gasket goes, below the face plate.

A build-up of salt/ corrosion and or flaking paint will create an uneven gasket surface.

I find it necessary to scrape that area with a razor blade scraper
to make a true flat surface for that gasket.

I also use some gasket compound on both sides of that gasket

This IS the suction side of the water pump

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

Yes, I had cleaned that area real good.
On the gasket under my NEW baseplate I coated the areas around the edges of the gasket ...from the edge about 1/4" inward all the way around.
Or should I paint the entire gasket and seal it to the (underside) of the baseplate.
I am using Mercruiser Perfect Seal compond.

Yes, the water is above the intakes (give me a little credit..lol) and up to the bottom of the cavitation plate which is about inline with just under the base of the pump.

I had another question too, the area around the outside of the pump housing, inside the upper gearcase is sealed, right? No water should go in there..even when the drive is totally underwater. I know that the physics of the water would push water up into the housing and force out any air therefore making the bubbles go away, but if the pump is leaking on the bottom area wouldn't it be causing a vacuume in the area around the pump in the upper gearcase?
If so this would answer another mystery I am trying to solve.

Kirk

 

[cdiamond]

Re: Mystery to be solved - reward to whoever gets it!

I understand about taking the boat a long distance
to put it in the water

But: if you are running it in a "tub"
you are going to have a lot of exhaust (air)
in that tub.
And I'm sure a good amount of turbulence

I doubt you are going to be able to
diagnose - air/bubbles in the output
from your pump with any real certainty

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

Well actuall there isn't much exhaust through the prop at 1000 rpms...
I can hardley see any bubbles comming up from the prop exhaust until I run it up higher (about 2K) then I can see exhaust bubbles from the lower unit in the tub.

I am now wondering if the exhaust port (in the drive) has a clog in it? Shouldn't I see exhaust bubbles even at idle in the tub?
Also when run on the muffs all that comes out through the exhaust was a very small stream (smaller than a pencil) when it was running. It seems it was more than that when new.

Maybe I have a pump sucking air AND a restriction in the exhaust.

I did run through some black mud in 2006 which caused me to have big problems (cracked heads) and just recently found some of that mud had hardened in the block water jacket around the base of the cylinder walls which I painstakingly cleaned out. It was about an inch deep. I thought it was rinsed out in 2006 but once the stuff hardened it was like concrete ...but I got it all out.
Maybe there is some restriction in the exhaust of this same mud.
Hard to imagine something with that large of a port being clogged though.

But I know exhaust gases in the tub were not the cause of the bubbles because as I said anything under 2K didn't show any exhaust bubbles in the tub.

I will check the exhaust while I have it off.


Thanks
Kirk

 

[cdiamond]

Re: Mystery to be solved - reward to whoever gets it!

It sounds like the majority
of your exhaust, must be exiting
from the relief ports, on the transom plate

Which is ok

The main thing I was concerned about
was introducing air into the tub

And you say that is not happening - that's good

 

[redjmp]

Re: Mystery to be solved - reward to whoever gets it!

Myself I think some of the problem might be the T-stat housing and specifically the balls.
Maybe you have a bent shaft and sticky balls?
If one ball is binding to the shaft just slightly in one spot, while the other works fine, then that would explain why one side heats up more. The ball not opening as much as the other one.

But when you pinch off the other line, now all the pressure is on the sticking ball which now has enough force to move a little further up the shaft and sticks there even if you unpinch the other hose allowing more flow than it normally would get, allowing that side to temporarirly run cool until you shut it down.
When you kill the engine, the spring pressure is enough to overcome the resistance the ball encounters on the shaft, returning it to the closed position.

Make sure that both balls slide freely up and down the shaft.

 

[KWG]

Re: Mystery to be solved - reward to whoever gets it!

This is a newer model tstat housing.
Without the balls.
See attached pic.
That one has been mentioned a couple other times.
Thanks for the try though ...please keep any ideas comming.

Thanks again
Kirk

 

[cdiamond]

Re: Mystery to be solved - reward to whoever gets it!

I don't think you need any more ideas

You have located a problem
with bubbles of air coming from your water pump

That is what you need to address