I have an 1988 OMC Cobra 2.3l I/O. I have had an overheating issue that I cannot figure out. I have replaced the outdrive water pump several times and have burn't out and replaced the waterpump case. When I run on muffs the temperature of the exhaust manifold runs at 120-130 degrees (normal I think). When I put the boat in the water the exhaust manifold temperature spikes quickly to 150 and higher. I have a thermocouple and a reading device to monitor this temperature. I blocked the cooling hose to the engine and put pressure at the water pump bleed hole on the outdrive. I checked for leaks around the pump housing for leaks (thinking it might be sucking air) but found none. I also submerged the outdrive in a tub of water and connected a vacuum pump at the waterpump vent hole, in the upper outdrive and tried to pull water from the bottom half of the outdrive. It did suck water, but had air bubbles in it.
This leads me to believe that one of the seals in the water tube that leads to the bottom of the outdrive intake water vents is leaking air. But, on the water the outdrive is completly submerged in water, so even if it was leaking, I think it would suck water which should not effect the prime to the pump.
So, before I pull the outdrive to check these seals I thought I would see if anyone else experienced this problem. Thanks.
This leads me to believe that one of the seals in the water tube that leads to the bottom of the outdrive intake water vents is leaking air. But, on the water the outdrive is completly submerged in water, so even if it was leaking, I think it would suck water which should not effect the prime to the pump.
So, before I pull the outdrive to check these seals I thought I would see if anyone else experienced this problem. Thanks.
