Engine Fresh Water Pump

[Sundance]

I think I have a very slight leak on my FW Pump. (See the Photo)  I was looking over the engine this past weekend and say this.  It looks like it originates from the FW Pump location.  I have read a few posts about replacing the pump with a rather inexpensive one from Kubota, but my question is, do I need a while new pump, or is just the gasket leaking?  If I am draining all the coolant and removing the pump to put on a new gasket should I just replace it?  I only have about 500hrs on my 25XP engine.  I have heard about peoples pumps freezing up, were there signs such as this small leak ahead of time, or did it just seize up without any prior indicators?  I ask because I would prefer to do this project in a few weeks when I have a little time.  Any thoughts or comments are welcome.  BTW, how difficult is this project, seems straight forward, but I may be missing something.

[Ken Juul]

From the picture it appears to be coming from the bolt which would indicate a bad gasket.  If it is just the gasket I would wait and replace it when I winterized the boat. But just to be sure I would carefully inspect the entire pump for other signs of the leak.  Use a mirror or remove the pulley to get a close look at the underside of the case. If it is coming out of the shaft and running down the pump case I would replace the pump before corrosion causes it to seize.

Replacement is very straight forward.  Drain the antifreeze.  Check the new pump, you may need to reuse the pulley.  If yes, it is easier to loosen the bolts before you remove the fan belt.  Remove fan belt, remove pump. Thoroughly clean the mounting area on the engine to remove any old gasket/rust.  Putty knife, chisel, sand paper all work well for this.  Install the new pump in the reverse order, add new antifreeze and burp the system.  Should take less than 45 minutes unless you take alot of refreshment breaks.

[Sundance]

Thanks Ken.  I did take a pretty good look at it, it does only appear to be coming from the one bolt.  Do you think it is worth replacing the whole pump while I have it apart, or just the gasket?  I read on the MB that these pumps generally should give you 1000-1500 hours, I should have 20-40 more years of service before I hit this, but if the part is cheap I can probably rationalize replacement now.

[Ron Hill]

Jeff : I'd first try tightening that leaking bolt and then the 3 other bolt holding the water pump to the engine.  It's worth a try and may just seal!!  Make sure that you tighten in an X pattern and all to about the same torque.  Think it's a #10 metric size.

Remove the drive belt and spin the pump pulley.  If it turns freely and silently the pump still has life in it and I wouldn't change it.  If you hear/feel binding definitely change out the pump. 
Be careful not to over tighten the drive belt, as that's the main cause of waterpump (bearing) failures. 
A few thoughts

[Sundance]

Ron, I think I'll give that try this weekend.  If it is just the gasket, do you think I should replace the whole pump while I have it apart?  I think I saw the pump for approximately $100, the gasket was $6.

[Ron Hill]

Jeff : If you do the check I recommend and all is OK, I wouldn't replace the water pump.  You might as well replace the coolant if you have to drain it to replace the gasket.
I believe that the Kubota gasket is only about $1? 
Just make sure that if you just replace the gasket, that both engine and pump surfaces are CLEAN.  Be careful with a putty knife as it can easily score the aluminum engine surface.  I'd use some of the Permatex hi temp (red) gasket sealer (thin layer) on both sides of the gasket.  Make sure you only tighten the pump down about 3/4 of the way.  Let the sealant cure and them tighten the bolts down (you don't want to squirt all of the sealant out)
A few thoughts.

[Stu Jackson]

Jeff, I'd posted this before, but couldn't find it so here it is again.  You can use the starboard petcock, or do it this way for saving your antifreeze for reuse.

The text includes burping the engine when everything's back together again.


Replacing Antifreeze and Burping Your Engine

A fellow skipper recently asked:  After five seasons I am thinking of changing the antifreeze in my M25. When I did it 5 years ago I recall having trouble removing air after the change. If I slowly drain from the petcock on the block and fill thru the plastic expansion tank simultaneously with the pressure cap off on the engine would this work so I don't introduce air?

I responded:  We just did this the other day when repairing the exhaust riser connection to the flange.  Don't bother with the petcock on the manifold, it's hard to catch the water.

Do this, shown in the photo, it's a lot easier.  Loosen the screw on the hose clamp of the big black hose underneath the freshwater pump and use a thin screwdriver to open up the space between the hose and the elbow.  Do it right from the front of the engine. You're right, take off the manifold cap when doing this.

As for the air block, it's called "BURPING" and all you need to do is take the 3/8 inch hose off the bottom of the thermostat.  Pour distilled water or antifreeze or the 50/50 mix into that hose with a funnel until water comes out of the bottom of the thermostat.  Loosen the hose clamp and pull the hose off.  Hold that hose up above the thermostat and pour the stuff into it until the water comes out of the bottom of the thermostat - the nipple that you just removed the hose from.  Once that happens, just put the hose back on the nipple under the thermostat housing and tighten up the hose clamp.  Put some Lanocote on the nipple to make it easier to remove the hose the next time. That gets the air out of the loop of hose that goes to the hot water heater and avoids overheating at startup and does not require that you rev the engine while the thermostat petcock is open.  You won't need to open the thermostat petcock at all.

Added:  Ron uses a Par hand pump - does the same thing.

{Added later}  Whoops, I did post it:  http://c34.org/bbs/index.php/topic,4518.0.html  Under "burping" not 'bucket"!!!

[Stu Jackson]

If it is just the gasket, do you think I should replace the whole pump while I have it apart?  I think I saw the pump for approximately $100, the gasket was $6.

I think Ron answered this in his Reply #3.  If the pump turns freely, it doesn't appear you need to buy a new pump.  If it doesn't, you do.

We have 2330 engine hours with the original pump.

[Stu Jackson]

One other thing, while you're at it, I would change the 1 inch to 7/8 inch special 90 degree elbow hose in your first picture.  It's still got Universal engine paint on it, and it's over 10 years old.  On our boat the INSIDE of that hose, that you can't see, rubbed against the engine and was nearing failure.  The rest of your hoses?  Up to you...

[Ron Hill]

Guys : A couple of thoughts:
1.When you drain the anti freeze don't reuse it!!  Antifreeze is cheap and you can't completely drain all of the entire system anyway!!  Use new anti freeze so you make sure the waterpump lubricant and the anti rust inhibitors levels are at "full strength".  You might consider using the "extended life" orange antifreeze!!
2. Make sure that lower hose into the internal coolant "water" pump is a formed reinforced hose as it's on the suction side (regular hose could/will collaps). 
I took mine off and went to an automotive store and found a perfect match for 1/4 the cost as Universal (wrote that up in the Mainsheet well over 15++ years ago)   

[Stu Jackson]

The reason I "saved" the antifreeze was that I had recently replaced it right before I had to do the exhaust riser.  I felt no reason to throw it away and replace with new, since it was already pretty new.  Your boat, your schedules!

It did, however, "force" me to look very carefully at the "L" hose, which is an unusual one since it changes size.

[Michael Shaner]

Would it happen to be frowned upon if, by chance, some desperate skipper were to top off a system containing green anitfreeze with a bit (ok, a pint) of the Dex cool orange antifreeze??   

[Braxton]

Here is a quick read on it:

http://autorepair.about.com/cs/coolingsystem/l/aa052601c.htm

It makes an unsubstantiated claim about possible aluminum corrosion issues.

[Ken Juul]

blowing up the picture it looks like it might possibly a previous leak from the hose.  Before you change the pump gasket you might want to clean it up and see if it reappears. 

[Stu Jackson]

Ken, that's very good detective work!   

It's also consistent with my suggestion about the hose in Reply #8.