Engine cooling

Mar 31, 2017
37
Hunter 31 31 Lake George ny
I have a Fresh water cooling system on my Hunter 31. I believe the engine is a Yanmar 2GM20F.
Right now I and getting an alarm for overheating. The hose to the raw water pump collapsed and it doesn't seem like I am getting enough water through the through hull going to the sea water strainer. I take the cover off the strainer and open the valve. How much water really should come out?
 

SG

.
Feb 11, 2017
1,670
J/Boat J/160 Annapolis
How much water should come out? Depends on the relative position of the top of the strainer to the sea level.

The hose to the raw water pump collapsed.
You mean the supply hose between the strainer (or before it) is flacid or what? I believe, if so, that hose needs to be replaced immediately. It should be too thick, reinforced, etc. for it to collapse or easily bend.

Do you have a photo of your set-up?


 

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Stop running the engine until you can fully inspect the raw system. That includes the intake hose, and thru-hull. You most definitely are NOT getting enough raw water. The hose is collapsing because it is either deteriorated or you have a plug in the raw water intake.
 
May 24, 2004
7,129
CC 30 South Florida
Remove the hose at the thru-hull and open the valve; the stream should be round and strong for 2-4 inches. If it is just a dribble or not very strong you have a likely blockage in the clam shell. I would first try compressed air to blow out what is plugging it. A few years ago I had a similar situation where we picked up a plastic ice bag. The thing is it was acting like a flap valve, we could blow air out but when water tried to get in the flap would close and obstruct flow. At the time we did not know what it was but diving under the boat revealed the culprit which was removed. Whether to first dive or try compressed air is your choice. Don't forget to inspect the raw water pump impeller.
 
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
Not to mention that the heat exchanger won't, and something expensive will melt as a likely result.
 
Oct 27, 2016
0
Seattle
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Oct 22, 2014
20,996
CAL 35 Cruiser #21 moored EVERETT WA
H3 You'se got trouble... I mean trouble... Trouble right here in River City...
Lots of water should be coming out. Hoses should not collapse.

Besides the strainer and the thru hull valve, do you have a grate on the outside of the thru hull? Something is blocking the inflow of water, causing the hose to collapse. (you will need a new hose... wire reinforced) Clear the blockage, check the raw water impeller, check the hoses and connections to the heat exchanger, check the heat exchanger... Why all of this extra? Because if the something blocked your intake then in all possibility some of the contaminant may have worked it's way further into the system. Breaking impeller arms or plugging the small tubes of the heat exchanger. Cool water is the savior of your engine.
 
Mar 31, 2017
37
Hunter 31 31 Lake George ny
I am going to take the raw water pump off to look at it, replace the suction hose, make sure the strainer is not clogged and look at the rest of the system for clogged heat exchanger.
 

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Take the end caps off the heat exchanger. If you can look through the tubes, great. If not, try fishing something soft through the tubes, like heavy, monofilament fishing line. There might be crud from the zinc clogging things up.

The collapsed hose could be just the hose! It certainly should be wire-reinforced.
 
Dec 1, 1999
2,391
Hunter 28.5 Chesapeake Bay
If the raw water hose really is "collapsed," my guess is that there is a blockage between the raw water pump and the raw water intake. As the impeller turns it would create suction on the intake hose and if no water is passing the hose might "collapse." A plastic bag or other solid trash stuck in the raw water thru-hull might be the cause.
 
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Mar 31, 2017
37
Hunter 31 31 Lake George ny
Thanks everyone.. I went to the boat, pulled the raw water pump and found the impeller was missing two veins, they were gammed in the discharge of the pump. Found the end of the raw water hose collapsed, looked like it was taken off too many times. pulled the hose off the sea chest and checked for flow, all was good, pulled the thermisat and heated it with a torch, works. pulled the end cap of the heat exchanger off, all was clean. back in business.. thanks
 
Oct 22, 2014
20,996
CAL 35 Cruiser #21 moored EVERETT WA
what do you use to report overheating engine temp?
DJ. I have a temp gauge on the engine panel. I also have a horn that sounds if temp reaches 200 degrees. Routine to check engine temp about every 45 minutes of engine use.
If temp shows above 170 I use a thermal temp gauge and test several identified places to compare against previous records.

Only time my temp alarm sounded was when the water pump shutdown. Blew the bearings. Emptied the engine coolant. Able to shut engine down and escape damage.
 
Oct 24, 2010
2,405
Hunter 30 Everett, WA
Thanks all: Im going to the boat wed night ill let you know what I find.
I found a .22 caliber gun cleaning rod with a brush on it fits the heat exchanger perfectly. At least it did on our 2GM20F
Ken
 
Oct 22, 2014
20,996
CAL 35 Cruiser #21 moored EVERETT WA
You have a good idea. The exchangers I have seen can be cleaned with a .22 cal rod or one of the new cable brushes pulled through the tubes with a wire cable.