Acid Flushing Fresh Water System?

[Captain Kirk]

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.


[Dave Neptune]

First yes you should have the double action t-stat for the "system" to work properly. I'd first try going without the t-stat and adjust the temp via "flow" with the bypass hose and a valve or clamp. I ran for 35 years without the t-stat and no problems.

It also looks to me as if you have oil gooping up the coolant passages and the goo coating does not allow for good heat transfer from the block and passages.

Dave Neptune

[sastanley]

I am with Dave...Try running with NO t-stat and see if it still gets hot??

[Captain Kirk]

First yes you should have the double action t-stat for the "system" to work properly. I'd first try going without the t-stat and adjust the temp via "flow" with the bypass hose and a valve or clamp. I ran for 35 years without the t-stat and no problems.

It also looks to me as if you have oil gooping up the coolant passages and the goo coating does not allow for good heat transfer from the block and passages.

Dave Neptune

Thanks Dave, I was thinking the same with the double action thermostat. Yes, the goop causing poor transfer of cooling makes sense. I hadn't considered that it could be oil in there. The 2 liter bottle of coolant that I extracted after the overheating occurrence doesn't appear to have any oil in it. I was actually thinking of filtering it and putting it back in the system once I get the coolant passages clean. There is a bypass valve already there which I should be able to control the temperature with. Being a V-drive, it's at the back of the motor so that if I want to adjust it after the initial warm-up I have to take the steps out in front of the motor and reach inside to get at it, way too much hassle, especially when I'm single handling. The double action thermostat should take care of that by itself.

[Captain Kirk]

I am with Dave...Try running with NO t-stat and see if it still gets hot??

Thanks, I will especially when running 'cleaner' through the system.

[zellerj]

My engine overheated for 20 years, usually running about 210 F. My flow out the back was good too. I finally solved it by taking off the alternator, distributer, and the side plate, revealing a bunch of junk crusted onto the cylinder walls. After picking out this junk as best I could, upon reinstalling everything, the engine ran at 140 F. Mark the direction the rotor is pointing so the distributer goes back in the same way it came out.

I know your boat has a heat exchanger and antifreeze in the engine, but perhaps it was raw water cooled for a number of years and junk accumulated around the cylinder walls and it was never removed.

IF you go this route be very careful not to break the bolts attaching the side plate, but if you do, fixes are available. I broke two of mine while doing this.

[Captain Kirk]

I am with Dave...Try running with NO t-stat and see if it still gets hot??

My engine overheated for 20 years, usually running about 210 F. My flow out the back was good too. I finally solved it by taking off the alternator, distributer, and the side plate, revealing a bunch of junk crusted onto the cylinder walls. After picking out this junk as best I could, upon reinstalling everything, the engine ran at 140 F. Mark the direction the rotor is pointing so the distributer goes back in the same way it came out.

I know your boat has a heat exchanger and antifreeze in the engine, but perhaps it was raw water cooled for a number of years and junk accumulated around the cylinder walls and it was never removed.

IF you go this route be very careful not to break the bolts attaching the side plate, but if you do, fixes are available. I broke two of mine while doing this.

Thanks a lot Jim. Thats certainly a spot I've been considering and avoided because of having to take the distributor off and of course the possibility of breaking the bolts on the side plate. It sounds like you didn't do a flush? and you were able to clear enough 'junk' to get the motor cooling properly. Good point about making sure the rotor is pointing the right direction in the distributor if I end up taking your route. I still want to try a flush first...Thanks again, Kirk

[zellerj]

I don't know your system, however just to caution you about the acid flush and recirculating the acid through your system. If you run the engine during this procedure, the exhaust will not be cooled by the water, and the hot exhaust can easily melt plastic water lift mufflers and rubber exhaust hoses.

[Captain Kirk]

I don't know your system, however just to caution you about the acid flush and recirculating the acid through your system. If you run the engine during this procedure, the exhaust will not be cooled by the water, and the hot exhaust can easily melt plastic water lift mufflers and rubber exhaust hoses.

Thanks Jim, I will just be running the acid through the anti freeze system by using an external pump hooked up to the exit hose from the Oberdorfer fresh water pump and out the exit port on the exhaust manifold which will dump back into the diluted acid bucket where it can be picked up again by the external pump and recirculated. I will block off the crossover valve as well to make sure fluid can get through the diverter valve on the side of the manifold. (here's hoping that's clear!) After a few cycles I'll run fresh water through from the dock hose to clean out the remaining guck. This way I won't be starting the motor at all. Still organizing hoses etc today. I may actually get everything hooked up tomorrow. In the meantime I've been cutting out the old hoses and fighting the new ones onto the nipples. I've also got the thermostat out and re-connected the housing. I'll either be buying double acting thermostat with the hope that my housing is ok or going with the indigo electronics external one, haven't got there yet.