Is this a bad idea?

[mmandwillsdad]

When I first cranked the 10 hp Yanmar on my 82 Hunter 27 this spring, it started with no problem; however, after running maybe 5 minutes the temperture light and buzzer went off. I immediately shut down the engine. When I inspected it, I found this metal cap under the engine and water coming out of the hole it popped out of. I closed the raw water value and the water stopped. When the engine was running, water seemed to be coming out the exhast as normal.

My plan is tap the cap back into the hole with a ball pein hammer. Is this a bad idea? Do I need professional intervention with this problem?

 

[kloudie1]

Generally, Core plugs like that should not be re-used. They deform on installation and will usually leak if ya try to re use.. It would be best to call your Yanmar guy and get a new plug. If you do decide to re-use it, your chance of success will be better if you.. clean the hole walls very well with fine sandpaper and then wipe down with a rag.. Clean the cap walls the same way. The cap should be coated around the outside walls with pipe dope. The concave side goes toward the engine and the outer walls should stop on a ledge in the bottom of the hole. You'll be looking then at the convex side as in the left-most picture. Don't use a ball pein hammer.. Take something about half the plug diameter, like a 3/8" socket extension and put it in the center of the plug .. Whack the round end of that extension (you can use the flat end of the ball pein to do that) to drive the flat side of the square end into the plug slightly, which should make the walls expand out a bit and squeeze snugly and leak proofedly (?) into the hole.. The dome of the plug should deform inward about 1/8".. if it isn't tight at that deformation, it won't get tight. and a new one will have to be fitted..

 

[Richard Bryer]

You should also check your antifreeze and or your procedures for winterizing- sounds like something might have frozen and caused that plug to pop -which is what they are supposed to do when things freeze

 

[tomgrigsby]

My Yanmar 3GMD is raw water cooled and I didn't drain it the first year. Same thing happened to me. As Kloudie noted I cleaned up the hole and popped it back into place. It's been fine for 2 years now. Being raw water cooled there is very little internal pressure in the cooling jacket, unlike the freshwater systems, so put er back and you should be just fine. Next winter just drain it down (better) and you can put some antifreeze in there if she's laid up for the winter.

 

[mmandwillsdad]

Thanks for the info. I will update on how the repair goes. Thanks again.