Raw Water Pump Cleaning and RW Blockage

[MFC]

Hi All -
Changing the impeller ion the RWP of my Universal and discovered a lot of corrosion and / or impeller debris on the engine side of the pump housing. I can break this gunk up with engine cleaner but I am concerned that there may be a set of lubricated bearings around the shaft and that the penetrating oil could somehow harm them. Thoughts on this? Suggestions?

Edit: reinstalled impeller and am still not getting water flow (water flows to the pump when I disconnect it but it is not reaching the exhaust . . .). What are the next "trouble shooting" steps for raw water blockage? Thanks.

TIA
Matt

[Jim Walsh]

If you have impeller debris evident I'd check the heat exchanger next. The pieces may have gone there or it may just be blocked from not having been cleaned in years.

[MFC]

Thanks. I seem to have water flow through the heat exchanger and up to the vented loop (although it looks like water flows through the heat exchanger in multiple paths). Then the water comes back to the top of what I think is called the "exhaust elbow" where the coolant reservoir and the exhaust water. What is the normal procedure for cleaning the heat exchanger. Thanks gfor your patience with the basic questions -- this is the first time I have done more to the cooling system than change the oil or the impeller.
Matt

[Jim Walsh]

It's relatively simple to remove the heat exchanger. Just bring it to your local radiator repair shop and they will dip it into a mild acid solution which will remove all of the deposits. I would remove the zinc and the two end caps beforehand. You will have to replace the end cap "O" rings (and the zinc if needed) when you reassemble it. If you are a perfectionist now would be the time to apply a coat of spray paint....it'll look brand new, and perform as new.
Someone is bound to chime in that you can do the whole thing yourself and not pay a radiator shop to "rot it out", be that as it may. The radiator shop has brushes and pressure washers which ensure all of the tubes in your heat exchanger are well scrubbed and scale free. I find its money well spent.

[mgphl52]

Before attacking the heat exchanger, check something that is much simpler: the inlet to the exhaust elbow!
Disconnect the line from heat exchanger (that goes to the elbow) and see if you can blow through it.
If you cannot or it's very difficult, remove the hose at the inlet and try to clean it out with a "special" tool: coat hanger wire, small screw driver, ice pick... whatever.
You may also want to replace the inlet nipple (is possible) or remove the mixing elbow and thoroughly clean it out.

Years ago, I replaced the custom muffler on KAYLA (MD7A) and started using a Yanmar mixing elbow. After selling her and buying back, she again was not pumping water... This time I found a stainless steel copy of the Yanmar elbow and switched from a 90 degree nipple to a straight nipple for easier cleaning.

Edit: link to post when I did the replacement

[MFC]

Thanks All -
Thanks to the laws of nature and boat maintenance and repair, I cleaned the strainer and the corroded water pump, replaced the impeller, changed a hose, removed and bathed the heat exchanger in vinegar (and changed the zinc) and then, after failing the"blow through it" test, I reamed the mixing elbow with a clothes hanger. Only after that last step was I able to get water flow through the engine and out the exhaust! Thanks for all the help . . . learned a lot.

Matt

[nessie]

Yay, it was the the exhaust elbow inlet for me as well last time!