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This Part Almost DESTROYED My YANMAR 3GM Engine!
17. august 2025 · 33 min · 15K visninger
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A damaged keyway on the crankshaft of a Yanmar 3GM30 engine nearly caused catastrophic timing failure, forcing a full engine rebuild on the sailboat Antidote.0:08 The keyway and key had been mashed together, allowing the timing gear to move on the shaft — a condition that cannot be tolerated.0:05 Rather than pay over $1,000 for a new crankshaft from Yanmar, Jon had machinist Gary in Texas machine a slightly oversized keyway and fabricate a custom stepped key sized to fit both the original gear and the enlarged slot.2:12 The repaired crank returned by UPS; Jon verified main bearing clearance at 1.5–2 thousandths of an inch using Plastigage, then confirmed with a dial bore gauge at 3 thousandths — both within the 1.1–3.4 thousandths spec.6:53 Big-end connecting rod bearings showed wear and were replaced with new shells from Parts for Engines.7:56 The engine block returned from the machine shop after hot-tanking and honing; cylinder ridge measurements came in under half a thousandth of an inch, within tolerance, so boring to the next oversize (0.25 mm) was deferred.13:43 A 3D-printed ABS bearing pusher successfully pressed out the rear main bearing for seal replacement.24:00 Stuck copper injector-bore crush washers in the rebuilt head required careful extraction.24:39 Proper oil-film clearance — too tight seizes metal, too loose bleeds pressure — is the central lesson threading through every bearing measurement here.8:25
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