I am considering purchasing a 2007 model yr. boat with these engines. Can anyone shed light on their quality, performance, problems, etc.
They're easy on fuel compared to C32's of that era. However, the 86' Johnson I would think would be hard on motors. It runs very bow high at cruise speed and only does 14-15 knots. In comparison the 105' with 16v2000's 2000 hp was same hull but stretched and got up and ran a solid 20-21 knots at 80% load. That particular boat had a lot of issues with those motors- coolant pump, starters, injectors, injector pump, etc.
From what I understand the M93 series was great in displacement hull vessels but had some issues in high load applications of a planning hull. Not familiar with your particular hull but saw some issues in 50 to 60ft Sportfish both 8v and 10v configurations.