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Flushing 8.1s and prop shaft seals

S

sandbars

New member
Was attempting to flush my motors today while the boat was up on a rack out of the water. A lot of water was coming from the propshaft seals area of each side, so I couldn't circulate. I have a hose coming from my heat exchanger (lower red arrow, below the zinc) to the shaft seal; can I just pinch this off or would this be the return line? There is another hose leaving the shaft that looks like it goes to the engine side, but i couldn't quite see. Should much water be draining from the shaft seal area when flushing the motor? (it was ~1 gallon every 15 seconds) The flush was set up with the sump output going into the oil cooler, then hoses from the water line feeding each exhaust elbow (big arrow in pic) were run to empty in the same bucket as the sump. Thanks

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not exactly sure what you are trying to accomplish .....????

The hose going to the shaft is raw water from the heat exchanger....you can pinch it off or pull it and plug it as long as the boat isn't floating.

The upper hose, feeding the elbow, is also raw water, but after a few more passes thru the heat exchanger...if the engine is running for more than a few seconds, you want cooling water flowing into the elbow to keep the exhaust hoses intact.

finally, not the best idea to supply the raw water pump from a hose.....the pump is capable of moving more water than most hoses can supply....
 
I'm trying to run a descaler through the raw water system before launch this year. The zincs had a bunch of buildup and boat has uncertain past. The engines aren't running during this process. I put a sump pump in a bucket of water, put the output into the oil cooler (just after water pump), then attach hoses from the two raw water feeds on the elbows that drain back into the bucket. There are a bunch of videos showing this working great, only i'm losing water in the cycle and found that it's draining from the dripless shaft seals. I'm trying to verify if the connection on the lower side of the heat exchanger is the source of water that feeds the seal or if it's the return.
 
ok...that explains it a lot better than the initial post.....

The fitting on the bottom of the heat exchanger provides the raw cooling water to the dripless seal....just pinch it off and you should be good for the descaler....FWIW, that's a one way circuit - there is no 'return' from the shaft seal.
 
There are two hoses going to each dripless seal, one hose goes to the HX and the other hose connects the two dripless seals together just in case you are running on only one engine, both seals will get "lubricated/cooled" with raw water. So you should only have to disconnect the hoses at each HX that go to each seal and plug or cap off the HX fitting. As long as the engines aren't running and the shafts are not turning, the water is not needed at the seals.
 
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