Raw Water System Failure

[dillehay]

We have a 2001 MKII with less than 500 hours, and the raw water output was extremely low when I started her up recently.  Water output is down to about 1/10th normal.  Exhaust fumes come out.  Trouble shooting so far we have checked or done the following:  the intake water filter didn't need it much but has been cleaned; water was determined to flow freely through the intake through-hull valve; the port-side cap at the end of the heat exchanger was removed and the interior found to be free of debris and looked clean; the pump impeller was replaced (though the old one looked OK; this has been done annually); we disconnected the hose from the output side of the siphon down stream from the heat exchanger and water flowed freely with the engine in idle; and with a flexible probe determined that the hose from the siphon to the exhaust manifold is clear.  Because there are no water leaks that show up in the bilge or anywhere we can see along the system, and because inspecting the water flow through the transparent top of the intake filter looks like there is very little flow, the problem is apparently a blockage or failure somewhere after the exhaust manifold.  We ran out of time in our search, but will take it up again soon.  Any thoughts, cautions, or suggestions?

[Fuzzy]

Dillehay:
How hot (what temperature) does your heat gauge read when it peaks?
Larry

[dillehay]

Larry,

Because the water output was so low I did not run the engine beyond the point when it reached 160 and began to climb after that.  I basically stopped when the temperature began to rise above what has been normal.  Should I allow it to rise further?  Any possible damage being created if I did so?  That was my concern.
Dillehay

[Fuzzy]

Dillehay:
You should be able to let it go to at least 180 or maybe even up to 200 degrees with no ill
effects to the engine.
Larry

[mregan]

On another forum, someone discovered their exhaust hose had de-laminated internally and was blocking the water from exhausting properly.  Maybe something to look at?

[Ron Hill]

dill : To help you find where or how much water is being pumped, try this:

Disconnect the raw water hose from the nipple in the exhaust riser and run the engine.  You'll need to plug the nipple to contain the exhaust fumes and you can only run the engine for a short time (without the raw cooling water) 
The raw water should really squirt out of that exhaust hose into a bucket.  I don't think your blockage is in the muffler.

Let us know if you get substantial water. Otherwise it sound as though you've checked all of the system.   Hope this helps

[dillehay]

Fuzzy, Mregan, Ron, thanks for your comments.  I will pursue them.  One concern I have is that a blockage beyond the exhaust manifold would create a back-up that could put water into the engine--much like trying to start the engine for more than 30 seconds.  Could this happen?  We already know water reaches the nipple at the exhaust manifold.  And it is reassuring that no water ran back out when we disconnected the hose from the output side of the siphon. 
     One thing I should have included in the original post is that there is the "swoosh, swaash" sound from the muffler area when the engine is running.  Much like the normal sound when things are operating correctly.  I did not try to pinpoint the source--muffler, pipes--at that time.  Probably means, given what else we have eliminated as possible causes of the failure--that water is reaching the muffler but not exiting.  But why it would not then back up the hose and pipe to the exhaust muffler?  Maybe that would take longer than the amount of time the engine ran?
     I'm thinking I should get a CO detector since there could be an exhaust leak into the aft cabin (part of the problem?), and we are at the point in the search of looking at and beyond the exhaust manifold.  Maybe the exhaust fan would take care of this concern?  Has there ever been a CO issue in the aft cabin that anyone knows about?
Thanks, Ron

[Stu Jackson]

Has there ever been a CO issue in the aft cabin that anyone knows about?

Ron, not inherently.  I've mentioned what I probably mistakenly call a "blow-by" which occurs on my boat from/at the connection of the exhaust riser pipe into the exhaust manifold at the flange.  The flange is tight to the manifold, but the nipple at the end of the exhaust riser is not perfectly tight into the flange.  This results in mild amounts of soot and a slight smell of exhaust in the aft cabin.  Either I take the whole thing off and rebed it or I plan to first slap some muffler pipe patch paste on the joint.  This is the only case of exhaust smell I've ever heard of on this board.

[Ken Juul]

Is your engine crankcase vent routed so that the engine injests the fumes?  If not that may be the source of your smell.  You have said you have good water flow to just before the muffler, so the problem must be in the muffler or in the exhaust tube between the muffler and the transom.  You may want pull the exhaust tube off the muffler and check for obstructions in the muffler output.  It might get a bit messy, but I would use a garden hose to squirt water down the exhaust hose and see if it come out at the transom.  If it is a partial blockage, the water may have enough force to blow it clear.

To alleviate your fears about water backing up into the engine, you can always drain your muffler between runs or leave the muffler drain open to ensure the muffler doesn't get too full.  Have plenty of ventilation if you choose to do this.

[Ron Hill]

Ron : I still think that you need to check the raw water output from the HX!! 
You can also do this by connecting a hose to the output of the HX and seeing what volumn is being pumped into a large bucket.

You can try Ken's suggestion, but the exhaust hose is about 1 1/2" inside diameter and it would take a very large something to block it.

The water that goes into the muffler has to come back out thru the exhaust.  If there were a muffler blockage I believe that the excess water would have already backed up in to the engine, but you can take either muffler hose off the muffler and measure (with a small stick) the water inside.

As far as blow by and worring about CO, you can check your clamp that attaches the exhaust riser to the engine.  Maybe you just need a new gasket inside that clamp?  Maybe the clamp just needs tightening?

I have a regular battery operated home CO detector.  Just remember to mount it low as CO is heavier than air. Mine is mounted under the bottom companion way step.

A few thoughts

[tonywright]

Two checks you have not mentioned so far.

You mentioned checking one end of the heat exchanger. Have you checked the hose that leads into the HX? There is sometimes debris blockage there where it enters the HX.

Others have described problems with gaskets on the face plate of the impeller housing after changing the impeller (which you said you did). If something is amiss there, you may not be getting good water pressure out of the water pump itself due to lack of a seal.

Tony

[Ron Hill]

Ron : As Tony mentioned go back and look VERY closely at you raw water pump.  Check the face plate for groves (you can reverse it), the paper gasket, the "O" ring and install another impeller. 
Look at the old impeller and make sure that the insert that attaches to the stainless shaft is still bonded to the "rubber".

[Mark Sutherland]

The fact that you thought the sloshing sound in the muffler seems "normal" would make me want to look beyond the muffler and make sure that the exhaust hose is not leaking between the muffler and the transom.  I had a hose clamp fail on my exhaust hose on my '86 which caused a leakage in/near the port lazarette.  I also recently serviced my HX and found remnants of zinc's inside the HX.  I'm not sure if these zinc remnants could cause a clog or not....  I would also want to confirm the output volume the RW pump.  Gook luck.

[Ron Hill]

dill : This may not apply to your engine, but it's worth checking!! Your boat is about the age where it could apply.

There is a Westerbeke Service Bulletin #235 that talks about a camshaft drive reinforcing sleeve for the raw water pump.  Look in Critical Updates and look at that Bulletin.

A thought - for owners of a M35BC engine with a manufacturing date (code E001) of Jan. 2000 or older!!