Atomic 4 overheating

kbgunn

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Sep 19, 2017
147
2006 Hunter 38 4410 Lake Lewisville, TX
I'm negotiating a 1982 Catalina 30 with an Atomic 4 gasoline engine that is raw water cooled. The survey was today and found only one major issue.

The engine overheated in the following way. Engine started and warmed up to about 160 degrees. Ran for 10 minutes at idle. Adequate cooling water discharge was observed. Surveyor shut down the engine for 30 mins. Started the engine. Warmed up to 160 at idle. Engaged forward gear and opened throttle to about 3500-4000 rpm. The engine overheated with temp spiking over 200. Shut down engine. Some soke from engine compartment and surface reading on the engine head were 210-220 at various places.

Any ideas what cause the overheating with cooling water flowing?

Every other aspect of the boat was solid.

Thanks,
KBG
 
Jul 6, 2013
172
Catalina 30TR, Atomic 4 2480 Milwaukee
Thermostat. The cooling water bypasses the manifold if the t-stat is stuck. Check Moyer Marine for replacement. The direct replacement for the original is very expensive, but they have an adapter that allows you to use a less expensive option.
 

kbgunn

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Sep 19, 2017
147
2006 Hunter 38 4410 Lake Lewisville, TX
Thanks @Kingjim91. That was my initial suspicion as well, but thought I would ask in case I was missing something. Reading on Moyer, the first step is to attempt cleaning by soaking in vinegar. I'll suggest this to the owner as the first resolution attempt. Inspection with the t-stat removed may show fouled cooling passages as well which are cleaned similarly....
 
Oct 10, 2011
619
Tartan 34C Toms River, New Jersey
Thanks @Kingjim91. That was my initial suspicion as well, but thought I would ask in case I was missing something. Reading on Moyer, the first step is to attempt cleaning by soaking in vinegar. I'll suggest this to the owner as the first resolution attempt. Inspection with the t-stat removed may show fouled cooling passages as well which are cleaned similarly....
I agree with Kingjim91, except I believe the problem is the cooling passages. I only say that because the motor did not overheat at idle. Did you check the impeller? The water pump seems to give enough cooling at idle but when revved it may not be getting enough. Just a thought as that situation happened to me.
 
Apr 5, 2009
1,620
Catalina '88 C30 tr/bs Oak Harbor, WA
If this is a raw water-cooled boat, it should have a 140º thermostat if it is in salt water so 160º is too high. Higher than that and you hit the salt precipitation temperature and the salt will crystalize on the insides of the water passages. It sounds to me like salt scale buildup in the cooling passages. It can sometimes be removed by filling the block with vinegar or Salt-away.
 
Jan 18, 2016
685
Catalina 387 Dana Point
...... Engaged forward gear and opened throttle to about 3500-4000 rpm. ...
Mine won't go over 2000 rpm in forward. I won't even rev the thing to 4000. I have an indigo prop, which will typically rev a bit higher than the 2 blade prop Catalina uses.

I second thermostat and blocked water passages.

A complete rebuild from Moyer is around $5400 so that's kinda the worst case option.
 

kbgunn

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Sep 19, 2017
147
2006 Hunter 38 4410 Lake Lewisville, TX
All good suggestions above which I will explore over the coming week. Thanks for the quick feedback. I haven't bought this boat yet, but it is a good contender if this issue gets resolved.
 
Nov 6, 2006
9,225
Hunter 34 Mandeville Louisiana
If the pump impeller, and cleaning of thermostat and passages dont do it (do that first), some more inexpensive things to check are ignition timing and valve tappet clearances.