MD17c cracked block - SailNet Community

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Old 09-11-2006
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Rockter will become famous soon enough
MD17c cracked block

I moved my olde MD17c to freshwater for the second time last spring,. Last wintrer, there was a spell of cold weather, dropping to about -14C, and the canal froze. I was not with the boat. The engine is raw water cooled.

I returned in the spring to find the core plug on the exhauset manifold blown out. I tapped it back in, and the engine ran fine.

On the first long run though I noticed a slow weep from the aftmost barrel, and it really does look like I have cracked the block. The crack weeps very slowly, and it worsens under load, but never more than about (say) a drip every 10 seconds or so. The crack is anout 1.1/2" above the cylinder base, and at the same height above the cylinder base as the drain plug, but on the forward right corner. The crack is behind the cylinder stud, so I can't really get to it. You can see the little bead of water forming on it.

The oil level is not rising, and water is not getting into the oil.

I have begun the process... a familiar one... of beginning to source the parts. I did a top end strip, in 1998, with re-bore and Mahle piston oversizes, so I reckon I can tackle it again. I met a fisherman who says he has a spare engine, though it is way to the north on the islands. I have long since given up even calling Volvo for spare parts of any size as they are so expensive, so the used engine is attrractive.

I only hope that Volvo have machined the barrels accurately so I do not have to go through the juggling of shims to set the compression. None of the barrels on the engine at present have shims.

I plan to source a sound barrel, drift out my (oversized barrel) and drift it into the replacement barrel. I will need new seals, of course, but they are not too expensive. I hope to be able to get the barrel over the piston again with the engine in position (not the way I did it last time).

Anyway, what's done is done, and it's my fault. Don't let your engine freeze.

The crack may not worsen, so I will watch it carefully, and fix it in the winter.

Your thoughts would be appreciated.
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Old 09-11-2006
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Rockter will become famous soon enough
I am reminded too, that cast iron is very, very difficult to weld. Apparently when the weld pool cools, it stresses the casting and cracks it again. It needs to be heated way up there to have a chance, and that will mean more expense.
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