water pump impeller -total destruction

[Ken Heyman]

After an idyllic sail, on Saturday,  we started the engine in preparation for returning to the harbor. After a couple of minutes of run time I noticed that "something" sounded amiss at the exhaust discharge. I peeked over the transom and discovered that no water was being discharged. I shut down the engine and sailed to our mooring. Wind direction and velocity were cooperative.

Upon inspection,water was coming into the fresh water filter from the sea and the strainer was not clogged. Upon removing the face place of the water pump, bits of pulverized impeller fell out. The outlet of the pump bound for the heat exchanger was 100% obstructed and the impeller 100% destroyed---nothing left but the hub. Also the pump housing was very hot so it must have been running "dry".I picked as much debris form the pump as I could get at with some "dental" type tools which worked very well. I did not mess with the heat exchanger or the hose from the pump to the HX. I installed a new impeller and voila -all seemed find. Healthy discharge and no overheating. I assume this is the acid test and there is no need to do anything further. I haven't run the engine under load yet but unless some debris breaks loose and fouls the system I assume that I am good to go.

I believe what must have happened (in that this impeller was relatively new and has been periodically inspected) was that I must have sucked up a plastic bag or something similar. It successfully blocked the raw water inlet until the pressure was released (once the impeller was destroyed and their was no suction). Then it simply floated away.

Lesson--keep a spare impeller on board and listen to the music of exhaust water being discharged.

[Ken Juul]

Been there done that   Those plastic bags will get you every time!! 

As a precaution I would remove the hose between the pump and the heat exhanger and make sure it is clean.  If you have any doubt, remove the input end of the heat exchanger and check there also.  When I cleaned my HE a couple years ago I found peices of blades that over the years (I'm blaming the POs) had come to rest in the HE blocking about half the cooling passages.

[Ken Heyman]

Thanks Ken,

I did see that suggested on the message board. I had difficulty removing the hose to the HX from the pump end but hopefully I'll get to that during the off-season. it does seem wise.

Ken

[Ron Hill]

Ken : Where the pieces of impeller blade/s usually hide - are in the lower hose elbow at the pump.  I'd recommend that you check that lower elbow.

[Ken Heyman]

actually Ron, based on your previous posts that I had read prior to the repair I did clean out that elbow. On Saturday we motor sailed while towing a dink to our winter resting place and all was fine with engine temp.

thanks,

Ken

[Clay Greene]

I would continue to monitor your engine temperatures to see if you are seeing signs of overheating.  We cured our chronic overheating problem by pulling three impeller fins out of the heat exchanger and a fourth out of the elbow off of the water pump.  I also could see how a fin could  become wedged in the hose leading from the water pump to the heat exchanger, although three of our fins had made the passage into the heat exchanger itself. 

We had a similar problem getting the hose off of the water pump and the heat exchanger.  Far worse were the other hoses leading to and from the heat exchanger.  A good channel pliers and some swearing did the trick.  The good news is that we coated up the connections with hose lubricant so it won't be such a pain next time. 

[Ron Hill]

Ken : What you need to do is get a better grade impeller.  If you have an Oberdoffer pump you can get a Barco #815 (made by the Globe Rubber Co) from Defender.  A thought