Onan marine genset (MDKD/MDKG series) service intervals

Onan MDKD/MDKG marine gensets follow an hours-based schedule with an annual minimum. Oil and oil filter: every 150 hours or annually. Fuel filter (Onan-branded, usually 149-2138 or similar): every 300 hours or annually. Air filter: inspect every 100 hours, replace when dirty. Coolant: every 3 years, use Fleetguard ES Compleat OAT. Impeller: every 500 hours or 2 years, Onan impellers on MDKD/MDKG are the #1 cause of "no cooling" complaints. Valve lash: every 500 hours. Belt: inspect every 100 hours. Anodes (zinc pencils in heat exchanger): inspect every 200 hours, replace when 50 percent consumed. Onan gensets require load-testing under real electrical load monthly, running unloaded for extended periods causes wet-stacking and injector fouling. Load bank or house AC + water heater simultaneously for 30 minutes minimum.