becoleman3
New member
I have an OMC 1987 4.3L GM V6 (432APARY) stern drive; cooling is a raw water system
This is run on an inland lake that has zebra mussels.
Towards the end of last season my engine was overheating. Since the intake screens were essentially gone I thought I had some obstructions and that this was probably the issue. When I was winterizing it was not overheating when the water flushers were used over the intake so I assumed what ever was obstructing had cleared.
This spring I decided to take the stern drive off, split the upper and lower units and install new screens. After reinstalling the stern drive I ran the unit again with the water flushers over the intake and again no overheating. I now realized that the water pressure from the hose pushed it into the engine.
I put the boat in the water and it began overheating. So I checked the impeller and some of the fins were torn off and so I replaced the entire pump and after running it began overheating again.
I pulled the intake hose off at the engine's thermostat and tried the water flow test and there was no water at all coming up. I then disconnected the hose at water tube of the transom mount and the tube was clear down to there. I then took the water pump off and back flowed from the thermostat and water came out freely and some fins from the impeller came out also.
I then attached the water flushers over the intake of the lower unit and the the water did not flow that fast out of where the water comes into the water pump. I also tried flushing water back down into the lower unit from the whole from the water pump and again it didn't seam to come out of the intake screens that significantly.
Since I replaced the screens in the lower unit and installed new seals for the water supply tube I have to think that there is a clog going from the water tube entering the upper unit to the pump.
Any thoughts or suggestions of what I should try to do.
In the past when I've had these clogs they had cleared themselves; does anyone have any ideas on how to do this?
This is run on an inland lake that has zebra mussels.
Towards the end of last season my engine was overheating. Since the intake screens were essentially gone I thought I had some obstructions and that this was probably the issue. When I was winterizing it was not overheating when the water flushers were used over the intake so I assumed what ever was obstructing had cleared.
This spring I decided to take the stern drive off, split the upper and lower units and install new screens. After reinstalling the stern drive I ran the unit again with the water flushers over the intake and again no overheating. I now realized that the water pressure from the hose pushed it into the engine.
I put the boat in the water and it began overheating. So I checked the impeller and some of the fins were torn off and so I replaced the entire pump and after running it began overheating again.
I pulled the intake hose off at the engine's thermostat and tried the water flow test and there was no water at all coming up. I then disconnected the hose at water tube of the transom mount and the tube was clear down to there. I then took the water pump off and back flowed from the thermostat and water came out freely and some fins from the impeller came out also.
I then attached the water flushers over the intake of the lower unit and the the water did not flow that fast out of where the water comes into the water pump. I also tried flushing water back down into the lower unit from the whole from the water pump and again it didn't seam to come out of the intake screens that significantly.
Since I replaced the screens in the lower unit and installed new seals for the water supply tube I have to think that there is a clog going from the water tube entering the upper unit to the pump.
Any thoughts or suggestions of what I should try to do.
In the past when I've had these clogs they had cleared themselves; does anyone have any ideas on how to do this?
