Overheating in '95 Mariner 225 caused by Lower Unit Corrosion?

rpmrpm1 · #1 August 2nd, 2003, 06:16 AM

Plagued by overheating at higher RPM's on port engine (some heat buildup on stbd too.) Did usual: new thermostats, new water pumps, rebuilt pressure relief valve - no real help. Engine rigging unchanged since installed in 1995.

Have seen internal corrosion at top of lower unit between water intake and exhaust passageways allowing seepage of hot exhaust into cool water intake. High RPM overheating fixed by patch. Suspect same problem now at different point in lower unit. Anyone with similar problems/experience?

Engines well maintained -350 hrs. Want to consider this lower unit corrosion before removal of cylinder heads or power head - could get expensive.

The Marine Doctor · #2 August 2nd, 2003, 07:56 AM

You might be able to change the baffle that separates the two chambers....also when you reassembled the gearcase to the leg...did you silicone the top of the baffle plate? This is a must as exhaust will pass through to the water side and cause overheat problems as it messes with the water flow.

TMD