Lost impeller blade

[KevinD]

Hi all,
So this is my second season with an Atomic 4 on my C&C 30. I changed the impeller yesterday for the first time and found the old impeller with a missing blade (see attached picture). I'm kicking myself for not inspecting this sooner. There is good water flow out the exhaust and running temp steady at just under 170.

But I'm worried where that blade (or parts of it) might be lodged? Any advice would be appreciated.

thanks in advance,
Kevin

thanks
Kevin

------
S/V Solevento
1980 C&C 30
Kingston

[JOHN COOKSON]

The first place to look is in the first 90 degree elbow right after the water pump - if there is one that is.

TRUE GRIT

[marthur]

That missing blade is somewhere, so you should follow the cooling system (starting at the pump) until you find it.

In my case, one of the previous owners lost a blade. I made this discovery a few days after I changed out the water pump. The new pump made more pressure and blew the blade fragment downstream-where it blocked water flow to the motor. Causing an overheat in the middle of Lake Huron on a calm day. It only took an hour to find the missing blade and restore normal cooling to the motor and we were in no danger, but it was an unwelcome discovery.

That's way better than the diesel blockage we discovered when delivering my new (1986) boat from Chicago to Muskegon--the fuel pickup was blocked by what looked like curdled milk. Took us completely by surprise because the diesel in the fuel filters looked great (I had checked before starting out). None of the chunks was small enough to make it past the screen in the tank to the filter! There was no fixing that until we could remove and clean the tank. Naturally, we were crossing Lake Michigan when it happened and we spent 19 hours becalmed in the middle of the lake. Maybe becalmed is a slight exaggeration, we did manage to go 1.75 miles during those 19 hours and had the barest of steerage for most of the time (not enough to show a speed on the knot-meter, though).

Stuff like that makes it a better adventure and I did get to show off to my dad by docking under sail But maybe you could avoid this particular type of adventure with a little work at the dock.

[sastanley]

I didn't want to state the obvious but since it has been, yeah...you need to find the missing vane.

[KevinD]

found the blade

Hi All, thanks for the advice. I took a look and found the blade. It was at the first elbow leaving the pump. Matched it to the old impeller and it looks like I got the whole missing piece. But I have a problem now - no water flowing through engine. I'll post a separate thread on that shortly. But here is the brief summary.
Went to boat today, started it and after a few minutes noticed no flow out the exhaust - just steam. Shut down the engine, took the impeller out and found the missing blade. Reconnected everything but still no flow. Thought I must have lost the prime for pump so I disconnected hose at pump inlet and sucked in till I had a flow of water into bilge, reconnected that hose. Still no flow. Verified that the pump was pumping by disconnecting hose on outlet side of pump and there was lots of water pumping through pump. Disconnected hose at entrance to where thermostat is and again, flow there too. I'm at a loss as to why I don't have flow now. and what to try next? Any ideas?

Kevin D.
SV Solevento
C&C 30
Kingston, ON

[Easy Rider]

Try removing the fitting at the aft end of the manifold where the water exits the manifold and see if it's clogged. Some crud might have dislodged when the engine overheated because of lack of flow. That fitting is known to plug up, especially on raw water cooled A4's, Good luck

[sdemore]

If you have flow to the thermostat input (presuming you mean via the bypass), then you only have a couple more things that it could be. Water leaves the thermostat housing and crosses over to the manifold, flows through the manifold and out the aft end, as Easy Rider discussed, and into the exhaust. When I was putting my engine together, I pour water into the manifold and have it move. Turned out the manifold was completely packed with rust and I had to clean it out to get any flow through it.

I would check the output from the manifold. If you have flow there, your problem is in the exhaust. If not, check the input to the manifold. If you have flow, the problem is in the manifold, if not, it is in the thermostat, housing, or hoses.

[KevinD]

exhaust manifold looks ok

Thank you very much for the advice. I took off the fitting at the exit of manifold and it looks ok. some rust in there, but not blocked. I removed the hose at the inlet to the manifold and was able to blow air through manifold (with hose to my mouth) fairly easily. I was going to take a look at the thermostat - removed the two bolts, but that thermostat housing is on there pretty snug - prying with a screwdriver did nothing to budge it.

By the way - how long would I expect to engine to run before water flows to exhaust if system was drained (by me removing impeller cover, hoses etc.)? In running engine to check flow I am worried about overheating and run until engine gets to 200 degrees, but I'm wondering if I'm not giving it enough time to fill with water?

And another question - do you think it is worth draining the system? There are two drain plugs - one near the exit of the exhaust manifold and the other on the other side near the impeller pump that drains the block - Any value in draining water to see if maybe I have an airlock or something someplace?

thanks again
Kevin

[JOHN COOKSON]

You can start at either end of the cooling system. Start removing hoses until you find where the flow stops.
There is a kicker though. There was a batch of impellers that were a tad to small in thickness and didn't work. If you have the old impeller compare it to the new impeller. As I recall the ones that didn't work were .020 to small in thickness. You might want to see if the water pump is actually pumping first.

TRUE GRIT

Edit: Discovered the other thread you started.

[thatch]

Congrat's on finding the entire impeller, that's a biggie. As far as rust goes, most of the time it will break off in pieces that look like "corn flakes". These flakes can migrate around and block fittings randomely while still passing the "air flow test". I realize that removing the manifold is a major project, but it's really the best way to be able to do an efficient rust removal job.
Tom

[KevinD]

Found problem

Thanks for all your help. I found the problem. I was losing prime at the strainer. I primed the hose running into pump by siphoning into bilge which I had done before to ensure the pump was getting a good supply of water. But this time I let it run into bilge for a few minutes and I could hear air noises at the strainer and then the flow just stopped. Lost the siphon. I think this has been my problem all along.

I was able to get flow bypassing the through hull and strainer and running a hose from a bucket of clean water directly to pump.

I took apart th strainer. It much debris in there but the seal at bottom was in poor condition and there was no seal at top. It's a Groco SVS 750. So I'm going to get some replacement gaskets.

Kevin