Stay Cool Pumps impeller repair kit Okay?

[Porchhound]

I used the stay cool pump kit that was onboard my C34 M25 engine (Oberdorfer pump).

I'm still having problems with my raw water system moving water out the exhaust although it did work again for awhile, one time. Once I shut the engine down and removed the strainer for inspection and cleaning it wouldn't pump water to the impeller the next time I started it. I have made certain my thru hull, strainer, and  inlet hose to pump were clear (yes, Stu I got a mouthful of tasty marina water!) I lubed the impeller and squirted dawn dish soap into the plug hole, but no bueno. I also blew through the hose to the HX and had some resistance, but no blockage. I got a great list of things that may be the problem from KW, but some of those pump and impeller housing issues are difficult to check out without replacing the pump and housing.

The photo is a before I cleaned up the housing cover. I lightly sanded the cover on a flat surface (220 grit) and then used sandpaper to remove the old gasket from the impeller housing frame.

Which leads me to question the impeller/gasket kit I used. I have a second kit also from Stay Cool Pumps.

I don't want to go out until I know exactly what the problem is, and that I can consistently start and run my engine when I need it.

[Stu Jackson]

What is a Stay Cool repair kit?  Is there some reason you didn't just use Oberdorfer parts and gaskets. 

[As an aside: you keep opening new threads for your recurring rw coolant issues, might you consider keeping this all in one place?  Like your HX thread?]

[Porchhound]

I used the kits that were onboard, making the assumption (ass-u-me") the PO knew what worked on his boat. I thought the threads went dead after a few days, but I will just add on...would be much easier.

I just re-checked everything one more time from thru hull to HX and the system started working. The only thing I did differently was to screw that impeller housing bolt tighter. I wonder if I should use some sealant on those threads?

[Stu Jackson]

....

I thought the threads went dead after a few days, but I will just add on...would be much easier.

....

They don't.  You can read ALL of them all the way back to when we started this forum in 2001.  That's why its search engine is so valuable.

It is also why we use LINKS so often and why the Critical Upgrades and 101 Topics and others are built around those links.

[Ron Hill]

Porch : You probably need to take off the O'doffer face plate and sand it down on a flat surface with wet/dry 200 paper.  Then replace the PAPER thin gasket and tighten all 4 of the bolts.  You mentioned some resistance in "blowing out" the exhaust line from the pump to the HX. Check the metal elbow on the pump to make sure there are no old impeller blades in that elbow.

Also there should be NO resistance in that pump to HX line!!  If there is you might have some old blades in it!! You might want to open up your HX and clean out all the debris!!

A few thoughts

[Jon W]

or broken blade bits in the HX itself. Finally got around to removing some from mine yesterday.

[Porchhound]

When I cleaned out the raw water strainer I guess the system lost its prime. The first time it happened I had just changed the impeller/gasket. I'm still not certain what fixes it...the system itself is simple. I just started it up again with no discharge  issues. We'll be off tomorrow for a few days if everything is well in the AM.

[Ron Hill]

Porch : You have an air leak somewhere in your raw water intake line - to be loosing prime!!

A thought

[Porchhound]

That has to be it. When I replaced the impeller I used a flat surface to smooth the face, but I didn't use the waterproof sandpaper. The only I could find locally now is 320 but I'll try it next. Do I need to put a thread sealer/tape on that little bolt that sits on top of the impeller case? It didn't have any when I removed it to squirt soap in there.

[KWKloeber]

some resistance in "blowing out" the exhaust line from the pump to the HX

Dave
Some resistance is not abnormal.  The amount is relative.    When you blow on the pump discharge hose to the Hx are you trying to evacuate any seawater that remains inside the Hx and/or in the hose up to the vented loop.  Beyond the loop it's downhill to the muffler so the hose will be empty.

Even if the Hx is empty the seawater path is through the relatively small diameter tubes that run from end-to-end inside the Hx.  They impart more backpressure than simply blowing through an empty 5/8" hose (virtually none.)  But there should be no "dead end" when you blow -- which would indicate a blockage somewhere.   

Make sure that there is nothing blocking any tubes in the Hx.  ALSO, check that the seawater injection wye into the muffler is open (not blocked with deposits.)  She NEEDS to run at 160F if in SALT.  Too high and deposits can separate out deposit out inside the injection wye.  It's better to run at 180F if in freshwater.

[KWKloeber]

...the system itself is simple.

The system is simple if following instructions and not using KNOCK OFF parts.  Sheesh I feel like I am talking to the back of my hand.

[Porchhound]

Ron, you were right. A friend who is a lead marine mechanic came over and spotted a couple things. Because the strainer is at a 90deg to the thru hull, when I cleaned it out it didn't want to fill back up unless I took the outflow hose that goes to the impeller housing off. There was an air lock. Secondly, the hose going from the strainer to the impeller housing was too large for the impeller fitting and couldn't be clamped down without leaving an air leak. The hose was tight on the strainer, but too big for the impeller housing. I can install a reducer to get the right size for the impeller and make sure I clamp the union tight so I don't cause a different air leak problem. Any other suggestions?

[KWKloeber]

EDITED

it didn't want to fill back up unless I took the outflow hose that goes to the impeller housing off. There was an air lock.

Secondly, the hose going from the strainer to the impeller housing was too large for the impeller fitting and couldn't be clamped down without leaving an air leak. The hose was tight on the strainer, but too big for the impeller housing. I can install a reducer to get the right size for the impeller and make sure I clamp the union tight so I don't cause a different air leak problem. Any other suggestions?

The airlock isn't in the strainer -- the pump is self-priming (so long as the impeller is lubed so it doesn't run dry.)  Air in the strainer is symptomatic not causational.  The airlock is in the PUMP because the impeller can't expel the air from the water chamber and create the vacuum needed to self-prime (draw water thru the strainer and hose to the pump.)   

Also, if the supply hose to the pump inlet elbow was leaking at the clamp then water below it (under pressure because it's below waterline) would would expel the air in the hose (up to the pump inlet) and water would flood the hose.

You may get it working as-is, but it may be unreliable with a problematic impeller.  There are several instances of the pump losing prime when heeled for a long period and it needing to be re-primed.  A knockoff impeller could be disastrous if you can't run the engine after a sail and the situation is dire.

The hose should be 5/8" on the pump hose elbows.  What size is the outlet hose barb on the strainer?  Every fitting adds resistance to flow, so don't use a reducer unless absolutely necessary ( i.e., fix what is wrong before jury-rigging it.)

All that said from afar w/o the benefit of hands on - it's a boat and anything can happen, even if it's contrary to Fluid Dynamics 101.

This thread may be helpful as well.
https://c34.org/bbs/index.php?topic=11044.0

[Dave DeAre]

Had the same problem on a friend's boat with an Oberdorfer pump. Turned out that the cover was distorted. Different/new cover solved the problem. Sanding/flattening the old cover did not help. My experience only.

[Porchhound]

I've ordered Oberdorfer impellers and gaskets.  When I start the engine, it will expel water initially, but then it goes down to very light spurts unless I have it at higher RPM, then it increases, tho the mechanic thought even then it should be discharging more water. The PO (Mel Lo) was on this site a lot as he worked on the boat, so I assumed the parts he bought were bonafide.

The inlet hose from the strainer is so large (5/8') it comes off and on the impeller housing with no resistance, and, being thick-walled, it can't be sealed on the elbow with the clamp. It fits tight on the strainer, as it should. The hose going from pump to the HX is 13mm (.51) quite a bit smaller than the 5/8 (.625) coming from the strainer.

After inspecting the hose end going to there pump, it looks ballooned out. I'm getting some calipers today to measure the ID. I may have to cut some off the end and reattach.