My 2002 SANTE 210 GT40 is hesitating at around 2,000 RPM. Runs fine higher than that though it's a not as fast as before. Recently the boat died in the water. Had the distributor and spark plugs replaced and the boat started but ran poorly. Shop suggested changing the spark plug wires-- seems to be running a bit better, but there is still a hesitation a around 2K RPM. Any ideas what to change next?