38-200 Overheating!

David Grimm

Squid!
Hey all. Sitting here at anchor waiting for the engine to cool down trying not to run aground. Ugh. Wind and tide both not working with me.

So over the winter I lost some coolant from that hose that goes to the top of the thermostat. Actually all the coolant that is in the box in the cockpit compartment.

So before it went in the water I fixed the leak and topped her off with coolant. I also flushed both sides of the heat exchanger, put a inline bleeder on highest point hose headed to the domestic water tank. Changed the rad cap, added a coolant ovetflow tank in the cockpit compartment, changed the impeller and cleaned the strainer. Bled the air out numerous times. Removed and tested the 160 thermostat. Stuck a wire down the exhaust elbow and doesn't appear to be blocked however the water out the exhaust seems weak. I have an oberdorfer pump that can only be mounted upside-down the apparently don't answer emails or advertise a phone number.

My water pump appears to be original. Have any of you seen them decompose and not work well?

Hope you all have a great healthy season, Dave
 

1911tex

Member III
David I had the same problem and this forum helped me...there is a second square radiator coolant box with radiator cap under the starboard settee on the afterdeck. I had no idea it was there. It was bone dry after I had changed the coolant and did everything you did. I filled it with 50/50 antifreeze and no problems since. Check it out.
 
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RCsailfast

Member II
Were you able to bleed the air out under the thermostat? That happened when to a Yanmar on a previous boat.
Would suspect with low water flow there may be an impeller issue. Wrong one or it may have just failed.

Hopefully you are able to locate a problem and make it to port safely
 

1911tex

Member III
Yes, the Oberdorfer......you stated you replaced the impeller. Correct?
Also:
 

toddster

Curator of Broken Parts
Blogs Author
Yes, the pumps do wear out. BTDT. If water goes around the impeller blades, pump no pump. It doesn't take much of a gap. Can you confirm that water is / is not flowing in the circuit?

1. Make sure that you've applied only one (1) paper gasket and scraped off all of the old sealant when changing the impeller.
2. If the impeller has worn a circular groove in the cover plate, water will leak around it. So far, I've been able to bring mine back to life by lapping the worn cover plate on a piece of sandpaper until the groove disappears.
 

David Grimm

Squid!
Well that was fun, limped back to the marina at 215 degrees! Not too bad. I've seen diesels run hotter. I'm going to try using the hand pump method described on the link above to remove any air pockets. ‍
 

Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
however the water out the exhaust seems weak.

Has the heat exchanger actually been "boiled out" in recent years? That's usually the starting point for this troubleshooting, if the Oberdorfer is working OK (Which you can check by detaching a hose and starting the engine briefly and hoping to see a good spout into a bucket).

Although diminished exhaust water can be many things, the HX needs to be eliminated first.
 

David Grimm

Squid!
I ran vinegar through the HX this winter with an electric pump. It ran fast and unrestricted. Ran two seperate gallons through for 15 min each. End caps off and looks spotless. Idk.

The raw water intake hose from the strainer feels cool to the oberdorfer and from the oberdorfer to the HX its cool. From HX to the exhaust elbow it's hot. So somthing is working just not well enough.
 
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Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
I am not contesting the evidence of good flow or pretending to be an expert. But allow me to say that 15 minutes of vinegar will not touch the calcium in a heat exchanger, which requires stronger stuff. Perhaps I am overemphsizing recent experience.

 

David Grimm

Squid!
Fixed! So when I took the input hose off the oberdorfer it just barely tricked water. I didn't know that wasn't normal but it raised suspicion. Pulled the strainer and it was as spotless as I had left it. Hmmm. So I closed up the strainer housing minus the strainer, pulled the input off the oberdorfer and connected it to the garden hose and turned it on. Few minutes later I could feel the garden hose flowing. Slight vibration through the hose. When I disconnected the garden hose I almost panicked with the flow of water coming from the strainer and quickly reattached it to the oberdorfer. Problem solved. Thanks guys.
 

1911tex

Member III
Please elaborate......maybe a plastic bag blocking the thru-hull valve intake? I have had that happen, that is why I watch the temp gauge religiously ! It's horrible that there is so much garbage floating in the waters now.
 

David Grimm

Squid!
It was an obstruction between the thrugh hull and the strainer. Not sure what it was but the garden hose blew it out. Probably a bag or zebra muscles. Idk. In the marina on the Hudson is not a place you want to jump in and have a look. Besides the water is 52 degrees!
 

Keith Parcells

Sustaining Member
Maybe just an air block. I have had it happen and had to squirt water from a hose through it. I got zero water flow prior to forcing water through, though. It was after being on the hard for 3-4 weeks.
 
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