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CapnRon47 06-21-2012 09:02 PM

destroyed impeller
 
I took my kids (I still call them kids even though they are in their 30's) on as crew in a sailboat race. They had never sailed let alone raced, but it was a social race and low key (well at least for me). I am trying to explain a hundred things as we leave the dock and I forget to open the seacock to the engine. About 5 minutes later the overheat buzzer comes on and I immediately know what the issue is (funny how you remember things you did not do then). Opening the seacock did not help, so I shut down and began working thru where the problem was. Water was coming in, but not getting to the engine was what I found, so I replaced the intake pump. Fortunately, I long ago realized tryiing to change an impeller on a Yanmar was an upside down and back-wards affair, so I carry a spare entire pump, with impeller and bracket. I just need to swap out the new for the old. To make a short story long it is not quite that easy as I have an extra belt on my 30 GM Yanmar for my fridge compressor. I have to take apart the main pulley to remove that belt, but I was ready for that and had packed a bunch of tools on board. I dropped the hook, which allowed me to later use my newly installed wash down pump, but that is an even longer story. And in about 30 minutes we were back on our way with water nicely flowing out the exhaust and the engine running no worse for wear, at least I have not noticed any degradation of performance. I motored home, about 2 hours, after the race weekend and had no issues.

When I got home I took apart the 'old' pump and found 4 of the six impeller blades still in the pump but un-attached. I am assuming the other two are working their way up into the heat exchanger and will eventually plug the mixing elbow. So I plan to back flush the heat exchanger to see if I can clean it out. Any thoughts, comments or suggestions on this procedure. I had not planned to open the end face plate of the heat exchanger, just flush it using the output and input hose connections. But I could be convinced otherwise.

thanks,
Ron

deniseO30 06-21-2012 09:18 PM

Re: destroyed impeller
 
someone needs to design a raw water sea valve that has a circuit interrupt to the starter switch. Glad you didn't have more damage then that Ron!

Faster 06-21-2012 09:39 PM

Re: destroyed impeller
 
Not real familiar with that engine, but if there's an end plate you might get lucky by simply opening up the intake end and finding the remaining bits stuck there rather than having found their way into the tube bundle... If you can account for all the bits you're good to go.

Oh.. and you've heard of the trick of storing the engine key on the through hull valve handle???? ;)

Flybyknight 06-21-2012 09:56 PM

Re: destroyed impeller
 
Might be a good time to clean the passages. In my other life as a chemical engineer we find that as little as 1/32" of scale reduces the heat transfer by 20%.

Dick

mitiempo 06-21-2012 09:59 PM

Re: destroyed impeller
 
Quote:

Originally Posted by deniseO30 (Post 887639)
someone needs to design a raw water sea valve that has a circuit interrupt to the starter switch. Glad you didn't have more damage then that Ron!

Not a good idea I don't think. There are times you want the intake closed when starting - with it open and prolonged cranking you could hydrolock the engine.

CapnRon47 06-21-2012 10:01 PM

Re: destroyed impeller
 
Denise,
I like the idea of a sensor on the input valve to start the engine. But, I usually prefer the simplest solution, the fact is I have NEVER done this before. I always open that valve and then check for the flow out of the exhaust before leaving my dock. But I was not at my dock and there were lots of distractions; the kids, other boats and backing out of a runway. Enough excuses, I messed up, but recovered. The boat next to me in the dock could not believe I changed the impeller while out in the channel, when I told him later. We missed the first race, but made it into the second. It actually worked out better as it gave me some time to work my new crew thru some tacks and jibes.

I can only assume my overtemp sensor went off before there was any real issue with the engine (what is the issue with on overheated diesel - running on?). I never saw any smoke or other indication of a problem with the engine. The engine always started right up as I was looking for the source of the problem.

Faster,
I store my engine key close to your suggestion, it is on the steps I have to remove to open the water intake valve. But not close enough this time.

thanks,
Ron

CapnRon47 06-21-2012 10:10 PM

Re: destroyed impeller
 
Dick,
That sounds like a good idea, but not sure how to go about cleaning the heat exchanger itself (the coils). I am usually an advocate of not fixing it if it is not broken, but you make a good point. I will have to dig out the engine manual to see how to remove the coils of the heat exchanger and whether it is worth that effort. After a little searching it seems I do not need to remove the coils to de-scale them. I can soak them in place with a chemical and then flush. Sounds like a good idea.

thanks,
Ron

Tempest 06-21-2012 10:10 PM

Re: destroyed impeller
 
I'm with Faster, I would open up the endcap on the inlet side of the heat exchanger, There's a good chance that you might find the pieces right there. You should probably have a new gasket handy.

travlineasy 06-21-2012 10:12 PM

Re: destroyed impeller
 
I agree with Ron. Never start the engine, inboard or outboard, without checking to see of the water is flowing.

Gary :cool:

CapnRon47 06-21-2012 10:21 PM

Re: destroyed impeller
 
Brian,
I was thinking more along the lines of the auto systems they had back in the 90's. When you would start the car it would say; "Your door is a jar!"

I could just image all the helpful comments we could a have on a sailboat designed by Detroit, well maybe I can't.


Ron


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