2002 6CTA (720 hours) Alum. in Oil Samples

I am looking at a 2002  42′ Silverton with twin 6CTA engines.   The oil sample came back with high levels of aluminum present in both motors.  The oil has approx. 40 hours of run time on it but we also do not know what brand was used during the last change.  I also find it odd that both engines samples came back so identical to one another.  Both engines turn over without any hesitation from a cold start.  There is no smoke when running, they both hit WOT at 2650 rpm, and there is no unusual knocking noises.    I understand that a single test is not worth much and it is possible to get a bad test back.   I am going t re sample and test the existing oil and than perform an oil change.  I need to determine weather or not I am going to move forward with the purchase of the boat.   What components of the motor are made of aluminum and would be contributing to this and how concerned should I be based on the 1st sample?