Shifting stuck studs
Mark Ryan demonstrates how, after trying a variety of methods, he finally managed to remove a sheared-off exhaust elbow bolt on his boat’s Yanmar 2GM20 engine
Removing a sheared-off exhaust elbow bolt
Ihave owned my Albin Ballad for near on 10 years now, and our little Yanmar 2GM20 engine has served us well over those years. I have serviced it religiously every year, although one thing I had never done since owning her was to take the exhaust elbow off to inspect it.
After reading in PBO that it was wise to do so as the inner sleeve of the exhaust elbow could fail at the flange with the engine and allow salt water into the block, effectively ruining the engine, I decided this year that it was time to get nasty with the elbow and take it off for an inspection.
My late father, Colin Ryan, was a shipwright and a marine engineer of much repute. Years ago, when he taught me to service my engine, he asserted how careful you need to be to guard against shearing bolts off into the head or block, conjuring up images of having to dissemble the engine into its constituent parts to allow for any sheared-off bolts to be carefully machined out. With this advice far from my mind, I soaked the exhaust elbow bolts for a few minutes in WD40 before putting a socket on the first bolt. I noted it was pretty tight, so I leaned gently on it and it cracked, then came out. I moved on to the next bolt and repeated the process. This one felt even tighter, so I leaned on it a little harder. All resistance suddenly gave way in that sickening, familiar feeling that I knew meant only one thing – the bolt had sheared off! My father’s words of warning now rang in my mind, and I recoiled from the engine with visions of needing to remove the head.
Helpful advice
I gingerly removed the final bolt holding the exhaust elbow on and the elbow came away, leaving the remains of the studding from the sheared-off bolt sticking conspicuously out of the engine.
I retired home to test the exhaust elbow (which, ironically, was perfectly fine) and then posted my dilemma on the PBO reader-toreader forums, where I was given many helpful pieces of advice as well as a remark that made me chuckle: ‘Yanmar make great engines cunningly held together with chocolate fastenings’.