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backofthemoon 07-03-2013 04:46 PM

atomic 4 cooling system
I'm having trouble with my A4 cooling system. I've changed the impeller and cleaned the filter that the water goes to from the thru hull before the water pump. I have taken out the thermostat and put it in a pot of boiling water and watched it open. I'm at a loss!! The motor is running too hot and there is definetly not enough water coming out the back of the boat. Does anybody have any ideas for Me? Thanks!

backofthemoon 07-03-2013 05:03 PM

Re: atomic 4 cooling system
I was thinking about by passing the filter or perhaps taking the thermostat out and seeing if that will increase the water flow

dinosdad 07-03-2013 05:24 PM

Re: atomic 4 cooling system
Possibilities , 1. Blockage in the raw water thruhull/screen area, 2. Internal buildup of crud in the cooling jackets of the block or exhaust , go to moyer marines website and do a search for more detailed information, they have discussed this very problem on that forum...

marianclaire 07-03-2013 06:27 PM

Re: atomic 4 cooling system
I second the idea of posting on the Moyer site. Moyer Marine Atomic 4 Engine Rebuilding and Parts Is your A-4 fresh water cooled, FWC, or raw water cooled, RWC? Early or late model? Do you have a by-pass set up. What is the maintenance history, any vinegar or acid flushes? Have you had a recent grounding stirring up mud? How old are the exhaust hose/pipes? You can work thru the system from thru hull to exit checking for flow and narrow down the search. Dan S/V Marian Claire

backofthemoon 07-03-2013 09:39 PM

Re: atomic 4 cooling system
This is the first boat I've owned with an A4. The boat is a1979 so I assume that it's a newer model atomic. I have not tried an engine flush but when I took off the thermostat housing I definetly noticed a lot of rust and dirt. There is no by pass but I will certainly try a vinegar or acid flush. I have noticed that some hoses were somewhat loose so I tightened what I could see. It seems to me that there is steam coming out the exhaust...and yes it is FWC

CalebD 07-03-2013 10:37 PM

Re: atomic 4 cooling system
Be careful with the designation FWC versus Raw Water Cooled (RWC). Raw water cooled means that your engine is cooled by water pulled from beneath the boat while Fresh Water Cooled really means that your engine is cooled by anti-freeze in a closed loop that mixes in a heat exchanger (HX) with sea/lake water to pass the heat out of the boat. Very confusing terms but very different. A lot of Atomic 4's are set up with RWC as it is the simplest set up, but not the best set up for the engine.
If you have a heat exchanger then your boat is FWC, if no HX then RWC.
Recommend overnight white vinegar flush of cooling passages. 1 gallon of white vinegar is about $2 in the supermarket.
Some A4 owners do operate their engines without a thermostat (T-stat).

backofthemoon 07-03-2013 10:46 PM

Re: atomic 4 cooling system
It is defiantly RWC. Thanks for the verification! I have thought about removing the thermostat but I don't think its a good idea to run the engine that cool. I'm sure for a short period it would be OK but I think it could do long term damage. I will try the vinegar and hopefully that will work. What are your thoughts on by passing the filter? I was going to run a hose from the thru hull directly to the water pump

tommays 07-04-2013 09:08 AM

Re: atomic 4 cooling system
The most likely water flow restriction is the exhaust manifold as it has small water passages and is the last place the water flows before leaving the block

backofthemoon 07-04-2013 09:15 AM

Re: atomic 4 cooling system
Tommays: what is the easiest way to clean the exhaust manifold? Should I run vinegar thru it or remove the manifold and clean/soak it by hand?

CalebD 07-04-2013 01:16 PM

Re: atomic 4 cooling system
The easy thing to do is to run the vinegar into the engine and let it sit for up to 1 day.
Taking the manifold off for cleaning is a much bigger effort as you'd have to disconnect the hot exhaust section - which does not like to come off cleanly.

There are plenty of A4 engines that run with no thermostat. Usually they have an extra valve in the cooling line that can be adjusted to force more water into the block. You can simulate this by putting a vice grip on the hose that leads into the T-stat housing.

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