My Universal 25XPB was overheating a bit at high rpm's. After eliminating all the usual suspects, I found pieces of the exchange pencil zincs in one of the passes. Scroll about halfway down here:
http://www.pbase.com/mainecruising/heat_exchanger My exchanger wasn't nearly as plugged as the one above. It really doesn't take much to affect the heat transfer in marine diesel heat exchangers. Heat exchangers are fairly critically designed. Pluggage in one or two tubes in one pass can significantly affect the effectiveness of the entire exchanger. The flow of water through the remaining tubes will increase. The increase in velocity through those tubes will reduce heat transfer, and so on and so on. Once I cleaned out the zinc pieces, the engine ran at temp again. Dennis C. Touche' 35-1 #83 Mandeville, LA On Sun, Jul 9, 2017 at 12:20 PM, svpegasus38 via CnC-List < cnc-list@cnc-list.com> wrote: > The full locker should not have been a factor, if the cooling system is > functioning properly. > I had to motor 45 miles one hot August day. Could only go 4kts (1400 rpm) > with the lazerett open. To keep the horn from sounding, i watched the yemp > guage and kept it at 200-204deg. The horn and light came on at 212deg. > Found out my heat exchanger tubes were over 50% plugged. > I cleaned them using muratic acid, and a long 1/8 drill bit to clean out > the tubes. > This solved my over heating problem. > >
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