Do Bravo drives "vacuum up" water?
07-12-2019 | 01:44 PM
#1
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From: Perdido Key, Madison, NC
Do Bravo drives "vacuum up" water?
I understand that it is deadly to the impeller to run an I/O without water for even a very short period of time.
So, when you drop your boat in the water (or get it off its trailer) and the lower unit is in the water at the start of a day of cruising...when you start the motor, does the impeller "self-prime" (essentially vacuum up water) to start pumping? So it starts dry and has enough vacuum/suction to pull water up to the impeller before damage/heat occurs?
Thanks,
Tom
So, when you drop your boat in the water (or get it off its trailer) and the lower unit is in the water at the start of a day of cruising...when you start the motor, does the impeller "self-prime" (essentially vacuum up water) to start pumping? So it starts dry and has enough vacuum/suction to pull water up to the impeller before damage/heat occurs?
Thanks,
Tom
07-12-2019 | 04:47 PM
#3
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From: SF Bay Area
Once a pump is primed it’s never fully dry as it has a head of water sitting on it from the hose to the engine, and the water level on a boat almost primes it as well. I’ve pulled the intake hose off the pump at the lake and water started flowing in.
As I understand it after about 30mph the pump is actually a restriction because the drive is shoving so much water through there.
As I understand it after about 30mph the pump is actually a restriction because the drive is shoving so much water through there.
07-12-2019 | 08:32 PM
#4
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From: Perdido Key, Madison, NC
So, would it be safe to run the motor (at idle) by lowering the Bravo drive into a tub/bucket of water (re-supplied by a water hose)?
Thanks again!
07-12-2019 | 09:09 PM
#5
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From: ALTO, MI
I would that in most boats yes the water level on the hull is above the seawater pump.
BUT even if the engine and pump were completely dry it would still suck water up and into the pump.
My engine is mounted high enough that my pump is higher than the water level outside my hull.
BUT even if the engine and pump were completely dry it would still suck water up and into the pump.
My engine is mounted high enough that my pump is higher than the water level outside my hull.
07-13-2019 | 12:15 AM
#6
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From: Thailand
I reckon my seawater pump is around about sea level. (Single engine). However, backed down the ramp, I'm sure it's above sea level so it depends on "vacuuming" water from the intakes on the drive. Never had a problem starting on the ramp with the stern of the boat in the water, I get full water flow pretty quickly.
Using ear muffs to flush the engine works fine and I reckon both sides of the impeller are dry if the boat has been sitting for a while. I'm sure evaporation will clear te water out. Running in a big trough, same thing applies.
RR
Using ear muffs to flush the engine works fine and I reckon both sides of the impeller are dry if the boat has been sitting for a while. I'm sure evaporation will clear te water out. Running in a big trough, same thing applies.
RR
07-13-2019 | 06:37 AM
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What are you trying to accomplish that a proper set of muffs can not?
Last edited by speicher lane; 07-13-2019 at 06:40 AM.
07-13-2019 | 08:29 AM
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Personally I never had a problem running on muffs, although I do like feeding into the sea strainer better.
07-13-2019 | 08:58 AM
#10
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From: Wisconsin
It only takes a small air leak between the pump and drive pickup to keep the pump from pulling water. Just a loose hose clamp can do it. You would think that you would see a water leak at that point when you are on plane at speed, but the pump pulls enough water that there is almost no pressure to the inlet side of the pump.
