Yanmar Diesel Over Heating

[Barrie McDonald]

I recently overhauled my coling system on my Hunter Legend 37 that is equiped with a Yanmar 35 hp diesel fresh water cooled engines that operates with a raw water heat exchanger.I replaced the impeller, cleaned out and repositioned the raw water strainer below the water line to improve water flow, replaced the mixing elbow and hoses and visually inspected the heat exchanger for any obstructions. I went from no water in my exhaust to plenty of water until yesterday, when suddenly my engine over heating alarm went off as I was motoring back to my slip.Once docked I checked for exhaust water and some was coming out but not as much as before. What could be the problem? I did notice some sea grass floating around, could I have plugged my intake or could it be something else.The raw water stainer appears to be clear of any debris. The engine performs beautifully but this lack of exhaust water is starting to bug me. Any suggestions would be most appreciated.Thanks Everyone,Barrie

 

[Steve Dion]

Similar thing happened to us.

Barrie:A similar thing happened to us last year. We had actually been stuck on a shoal and kicked up some rocks(gravel) which got sucked up into the raw water intake. When we took off for SF Bay the following weekend the overheat alarm went off. We immediately turn off the engine and let it cool off. We then restarted the engine and limped back to the harbor. Upon inspecting the strainer I found NO water comming in through the seacock. I pulled the hose off, ran a piece of wire down the fitting and cleared the intake. It's been fine ever since.Hope yours is this easy.

 

[Roy Mosteller]

One Thing To Check

Having lost water flow several times in recent years I always start by disconnecting the hose on the intake side of the raw water strainer to insure the hose is free of debris. Sometimes it is not.

 

[Paul Sealock]

Eel Grass

Barrie, Anytime you motor in your neck of the woods, you will encounter eel grass up the raw water intake through hull. I know from experience. Cklose the thru hull and remove hose to strainer. Then open seacock to see how much water is flowing. A lot means the thru hull is clear. If not, take a water hose and jam onto the elbow and turn on water pressure. this should clear the clog. (Make sure seacock is open at the time.)If this doesn't work, remove hose to strainer and make sure it is free of clog by running water thru it. (Outside on dock.) After that, check pump impeller and beyond.

 

[Gary]

Pacific NW grass

This is the time of the year in the Pacific NW when the eel grass seems to be a major problem.The grass plugs at the thru-hull, hose or in sea strainer. First I check the sea strainer and if no grass, then I disconnect the raw water hose before it goes into the pump, then blow out the line (blowing toward the intake). I can do the process in less than 10 minutes now). You have to put strainer back together before blowing. If the grass is really plugged, I disconnect the hose at the thru-hull and use a phillip screw driver to get out the grass.Gary

 

[Barrie McDonald]

Eel Grass the Culprit

Thanks Paul Sealock,You were right. I used my garden hose and clear the plug.Many thanks,Barrie