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No water circulation in BF75

mtcaddis

New member
Hello,
I just bought an old BF75 four-stroke 7.5HP outboard and I noticed there is no water circulation. The inlet screen seems to be unobstructed. I can't seem to figure out the path that water takes in the engine. I see a tube exiting the bottom of the engine compartment on the port side and there is air blowing out of it but no water at all. There is no air or water coming out of the tube that exits in the rear on the starboard side (this seems like it should be the flow indicator so I don't know what that other outlet is on the port side). There are two holes in the back of the lower unit and once it was spraying a mist of water out of it and the next time I tried to start the motor there was exhaust fumes shooting out both holes. I can also tell by looking at the fading of the paint on the lower unit that at one time someone had something covering up those two holes on the lower unit and I can see where they had huge hose clamps wrapped around the entire lower unit to hold something over those holes. I am ordering a repair manual but was wondering if anyone had any advice of where to start. Thanks!
 
I think the port hose is a crankcase vent. The starboard side should be the water indicator.

Be sure to only run the motor in a tank with the water almost 1/2 way up the motor, not just covering the intakes. The water has to cover the water pump also.

Most likely, the water pump in the lower unit is fried and needs to be changed. When you get your manual, some of the rear pages will show a diagram of the water flow so that you better understand it.

The manual will also be helpful in removing your lower unit.

If I remember right, some of those motors have a hose that runs from the lower starboard side of the engine, over the engine, to the thermostat housing. These has a tendency of plugging up right were it comes out of the engine on the starboard side. If you pull the hose going to the thermostat, there should be water coming out. You might be able to blow compressed air back through it to clear it....but if the impeller is in pieces some of those pieces could be blocking the passage.

Now for the huge hose clamps wrapped around the lower..... The two holes that you are referring to are most likely exhaust reliefs. I have heard in many cases, when these engines are enclosed in a well in some sailboats. The exhaust fills the well and causes the engine to fail. Some creative sailors have rigged "exhaust pipes" to these holes so that the exhaust is not captured in the well. Just a guess.

Mike
 
Thank you so much for the response! When I was running the motor I only had the water level barely covering up the intake and did not even realize that the level would need to be higher in order to prime the pump. I will have to try it again with a bigger bucket. I did pull off that crossover tube and it is all clear. The manual does clear up a lot of things. That makes total sense about the exhaust reliefs for people using it in a sailboat. Now back to tinkering...
 
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