Low water pickup depth below bottom
12-09-2014, 07:11 PM
#21
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Been there done that even tried modifying low water pickup on the drive. Nothing worked. Had a transom mount pickup right off the bottom of the hull (boxed one just like everyone else) no go. I think the steps out a lot of air in the water I was seeing 18psi with drive pickup and flush transom hull pickup. Motor would get hot. Only thing that worked was burying the pickup. I talked to a guy that has rigged a ton of boats he said sometimes you get a hull with these issues.
12-09-2014, 08:28 PM
#22
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There is a proper way of setting up an offshore pick up. There are adjustable ones and others that have to be ground. In most cases the trailing edge should be around 1/16 to 1/4 " below the bottom. The best way to determine the X height is to pace a Tee & a 0 to 15 psi gauge between your pick up & sea pump; and have a water pressure gauge for the motor. You need NO MORE then 5psi ram pressure @WOT. anything more is just a waste and will be a speed loss. When I did testing of sea pumps on a pump dyno, the magic # was 5 psi @ wot. Then check your block pressure. Anything from 10 to 30spi is good there, don't get all hung up on thinking you need a ton of block pressure, you have the biggest supply of cooling water. If your worried about steam pockets drill & tap the back of the intake for air bleeds. If your pick up is more than 1/2 dragging, then fix your bottom. I have seen guys run high block pressure & blow buy in intake gasket &/or wonder why they have water in the bilge after a run???
Oh forgot to add you also can do this with the drive pick up by drilling and tapping s/s set screws in the holes or add hole as needed. Its all in the fine details guys & taking the time to do thinks right; NOT "its ok it works for me"....
Oh forgot to add you also can do this with the drive pick up by drilling and tapping s/s set screws in the holes or add hole as needed. Its all in the fine details guys & taking the time to do thinks right; NOT "its ok it works for me"....
Last edited by Bawana; 12-09-2014 at 08:33 PM.
12-09-2014, 08:38 PM
#23
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There is a proper way of setting up an offshore pick up. There are adjustable ones and others that have to be ground. In most cases the trailing edge should be around 1/16 to 1/4 " below the bottom. The best way to determine the X height is to pace a Tee & a 0 to 15 psi gauge between your pick up & sea pump; and have a water pressure gauge for the motor. You need NO MORE then 5psi ram pressure @WOT. anything more is just a waste and will be a speed loss. When I did testing of sea pumps on a pump dyno, the magic # was 5 psi @ wot. Then check your block pressure. Anything from 10 to 30spi is good there, don't get all hung up on thinking you need a ton of block pressure, you have the biggest supply of cooling water. If your worried about steam pockets drill & tap the back of the intake for air bleeds. If your pick up is more than 1/2 dragging, then fix your bottom. I have seen guys run high block pressure & blow buy in intake gasket &/or wonder why they have water in the bilge after a run???
Oh forgot to add you also can do this with the drive pick up by drilling and tapping s/s set screws in the holes or add hole as needed. Its all in the fine details guys & taking the time to do thinks right; NOT "its ok it works for me"....
Oh forgot to add you also can do this with the drive pick up by drilling and tapping s/s set screws in the holes or add hole as needed. Its all in the fine details guys & taking the time to do thinks right; NOT "its ok it works for me"....
12-14-2014, 09:22 AM
#26
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Where is the proper location of water pressure readings? Mine is right after the freshwater pump on the PS cooler and before the engine oil cooler which acts as a strainer somewhat since the exchanger holes are only about 1/8 to 3/16". I am going to move it to the engine as I think the reading should come after the engine oil cooler which can restrict the water.
Should it be on the thermostat housing below the thermostat, or down on the block?
Should there be much difference in pressure between these two locations? Assuming a clean block.
Should it be on the thermostat housing below the thermostat, or down on the block?
Should there be much difference in pressure between these two locations? Assuming a clean block.
12-14-2014, 10:43 AM
#27
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Where is the proper location of water pressure readings? Mine is right after the freshwater pump on the PS cooler and before the engine oil cooler which acts as a strainer somewhat since the exchanger holes are only about 1/8 to 3/16". I am going to move it to the engine as I think the reading should come after the engine oil cooler which can restrict the water.
Should it be on the thermostat housing below the thermostat, or down on the block?
Should there be much difference in pressure between these two locations? Assuming a clean block.
Should it be on the thermostat housing below the thermostat, or down on the block?
Should there be much difference in pressure between these two locations? Assuming a clean block.
)))))))) just playing
