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Old 10-30-2022, 06:07 PM
Captain Kirk Captain Kirk is offline
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Join Date: Aug 2022
Location: Duncan, BC
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Acid Flushing Fresh Water System?

My first post, please bare with me. I am a new owner of a Cal 34 with a late model atomic 4 with fresh water cooling.
My engine has been seriously overheating. The last time out it registered 250 degrees before I shut it down. The previous owner (61 engine hours ago) spent $8000 Canadian on dealing with the engine overheating problem; boiled and flushed the heat exchanger with acid dip to remove deposits, replaced the manifold and block off gaskets and replaced the exhaust tower to name a few repairs.
There is lots of raw water coming out of the exhaust pipe at the stern with no apparent steam. The last time I looked ( about 10 engine hours ago) the fresh water impeller on the Oberdorfer looked fine. The last time I was down at the boat I took off the exit hose for the Oberdorfer and ran the motor for a few turns and the antifreeze flowed quite freely. I then spend a couple of hours removing the thermostat housing (it’s a V-drive with the thermostat at the stern end). It turns out that the thermostat is a 3 spring Holly single action which doesn’t move until it reaches 180 degrees (tested at home). It looks like the housing was designed for a double action thermostat which when fully opened with shut of the intake at the top of the housing so I guess I’m going to have to replace the Holly with either the Moyer double action one or go with the Indigo system. The housing itself was full of gunk and from what I can see in the hole beneath it, there is a lot of gunk in the cooling jacket, if that is what it is called under the the thermostat housing. I’m surprised it looks like this after all the work that was done 61 hours ago?
I’ve read Don’s description for flushing the raw water system in the MM1 manual and all sounds good, but it doesn’t say anything about how to clean out a fresh water system. I am thinking of putting my intake hose from the heat exchanger in a 5 gallon bucket of diluted muriatic acid (after shutting off my bypass hose valve to the thermostat and re-attaching the thermostat housing) and attaching another hose to the the exhaust manifold exit port into another bucket to capture the diluted acid when it comes out.
I haven’t taken off the side jacket to see if the diverter valve is clogged. It looks like I would have to take off the distributor with it’s brand new Indigo electronic ignition in place to get at the forward bolt. I really don’t want to have to do that if I can hep it. Any suggestions before I go any further are welcome.
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