Re: Yanmar 2QM15: How can I keep it running forever?
They let it sit in a tank of hot solvent, all of the carbon and deposits dissolve. Usually the longer you can let it sit there the better. I left mine for about 1 full day and it came out perfectly clean. I painted it yanmar grey.
Machine shops will usually "tank" blocks, heads, manifolds etc as a way to get them clean, or in some cases as the first step in getting them clean (with sand or bead blasting next).
1977 Bristol 29.9