I have a Ski Nautique we decided to repower with a new, factory re-built 351 Ford engine. This is an old (1974), straight inboard boat. The old engine had a lot of crankcase pressure and was blowing oil out. Otherwise it ran great. <br />We bought an engine, ordering a counter rotation 351. When it arrived, we installed it and when trying to put in the distributor, realized it was a standard rotation engine. Sent it back after receiving the correct engine. Installed this engine, cranked it up and began the break-in. The first time we exceed 2,000 rpm's it starts to knock. We eliminated all possibilities, leading us t the conclusion it was a main bearing knock. The supplier sent us another engine which we installed with extra care. Thoroughly cleaned everything. Primed the engine thoroughly. Within a matter of hours, and again when first accelerating beyond 2,000 rpm's, it starts to knock. Same knock.<br />We call back the supplier and they tell us the first engine failed due to a lack of lubrication in # 8. And it's our fault. I can't figure how they determined this. Both engines always had0 oil pressure. The only way I see that I could cause a lack of lubrication is by not putting oil in the engine. And if that was the case, there would be a lack of lubrication everywhere, not just # 8.<br />We pull out the second engine and do a little investigation. They had subsequently told me that the rear main bearing on the first engine was bad. We take off all the main bearing caps and all are good except the rear one. It's smoked. The rod bearings being fed oil behind this bearing are undamaged. This indicated to me that there was no "lack of lubrication" to that bearing but something else was obviously wrong with both engines. Any ideas? I need the opinion of an unbiased, Ford (counter-rotation), mechanic. <br />We're still waiting to hear if they plan on standing behind their warrantee. I just want to make sure this won't happen again. We've installed this engine 3 times now. I want the next time to be the last.