Well I purchased a pair of engines which were posted here. we live in the caribbean and in order to ship em out of the US was a nightmare as the seller did not want to cooperate. ANYWAY , we got the engines here which are 540 Cuin rated at 650 HP built by TRISTAR engines out of WI. I spoke in length to the manufacturer whom recomended a break in period of 10 HRS using Mineral 15W-50 oil there were also some guidelines as to no less than 1500 RPM and no more than 85% of WOT which works out to 5100 RPM . in the process of breaking in the engine one of the engines scattered doing 5000 rpm. Number 8 connecting rod parted from the crank and broke everything inside of there. I called tristar and their first response was "you are aware its out of warranty" .. no concern how their garbage had exploded after only 6 hrs. I then asked if they can supply a short block to match the other engine... response was "well i want to help you but if i do now i have to help you if something goes with the other engine"... he siad he will call me back and well no response yet. we then took it upon ourselves to tear apart the bottom end of the good engine to find that the clearances were way to tight to begin. the blocks were not prepped or cleaned properly, there was lose filings of metal all over the engine block and crank. when i say loose i mean still attached but could flake off at any point. all the bearings were worn badly and the same number 8 journal had already worn down .030 and it was a matter of time that the engine blew up as well. They also had placed assembly lube on the back of each bearing (both mains and connecting rods) which when the stagnated oil burns it tightens the clearances even more. Tristar will not stand by the **** they produced and it was evident that they simply slapped the engines together with ZERO care. They used great parts but did a hack assembly job. They no longer offer marine engines i guess i can see why.