Bravo One water impeller
 

I know that the Alpha One operates with a water impeller in the outdrive.

Does the Bravo One also have an impeller in the drive in addition to the water impeller pump mounted on the engine? What is drawing the water up from the drive to the motor? Is it by just suction from the engine mounted pump?

You are correct, just the one on the engine. Its crazy how they work, alot of good videos on youtube.

No a Bravo does not have a impeller in the drive, and neither Alpha nor any other boat impeller "sucks".
The impeller moves water from one side to the other. This is a reason you cannot run a drive in a bucket or drum. Some do this with the Alpha but even then the impeller is running somewhat dry.

Only motor which can be run from a bucket is the outboard

When the boat is in the water, the drive is submerged enough to bring the water to the impeller. When moving the intake holes on the drive are angled forward to force the water to the impeller

The above video clearly shows otherwise. Put your hand over the intake side of a Bravo 1 pump and rotate it. Submersion depth of intake holes and forward motion of boat only enhance pump flow but are not requirements.

most Mercury outboards use nearly an identical pump to an alpha. The pumps absolutely do have suction and will draw from a bucket etc. Many boats have the water pump above the water line.

Agree with above. An automotive water pump, or the circulating water pumps on the front of our engines, have metal impellers that do not create a seal to the pump body. This type of water pump is what AllDodge is referring to, this sort of pump does not create suction or pressure. Instead, they simply create flow.

The rubber impellers in a tight-tolerance housing, create a seal to the housing, allowing for the creation of negative pressure (suction).

My pumps create suction as soon as the engines start I can see the water going through the intercooler dumps as soon as they light up .

Bravo One water impeller
 

Wait. When a boat is in the water and drive submerged, does the water reach the engine mounted pump? I would think the water in the drive would be lower that the impeller meaning there is suction involved.

With boat in the water remove the hose going to the pump

While there is some its very little suction. There is all kinds of threads here where folks have trouble getting a slightly used impeller to pump. Ya'll have your opinions and I have mine, they don't agree but what else is new.

Anyone with a Bravo, with boat on the hard put your drive in a bucket. Fire it up and see how long your impeller last, I'll wait

Bravo One water impe
 

Remember, when you back your boat into the lake, your drive is submerged but your water impeller pump on the motor still is above the water level line. When you start the motor , it take a bit of time for the water to exit the exhaust.

Thanks

Ive done it...but we used a bilge pump to help prime the lines while cranking...once its going it will take water in by itself :D

No

I've run my Bravos numerous times in a plastic 55 gallon drum laying longwise on the ground with a slit cut in it to fit the drive in and just the water hose filling the drum, no muffs.
It always pumps water.
I do it just to ensure the impellers are indeed drawing water.

Grand Dad always said first lair doesn't stand a chance

Clearly the video shows otherwise, but that does not sway you. I have personally run an engine on a stand with the intake hose from the Bravo 1 pump stuck into a large container of water below the pump level. Not only did does it draw up the water quickly it does so in copious amounts. It pumps out water at idle faster than my garden hose could fill the container. Pump is fine. The vane pump by design will draw water up to it.

I ran a kohler generator about 5 hours this week with the pump sucking out of a 55 gallon drum.
And then there’s this kit for winterizing

Everyone better return there outdrive earmuffs…clearly they won’t work

I don't often flush my boat. but when I do, I make it suck water out a hose in a dark alley.

https://southpark.cc.com/video-clips...-out-of-a-hose

I need to call this one out too, having 496's, when those brass end plates have groves in them from wear, they don't prime because the clearances don't allow "suction"
this is why the rebuild kits feature new end plates and why the Hardin stainless pumps are so much better
That said I've personally seen a 496 with bravo 3 run on the trailer in a 55 gallon drum of water, it's the exact same scenario as the boat sitting in the water, this is also why they say not to run an engine on the muffs faster than idle speed, because the pump will suck the water faster than the hose can supply it

I never had any luck using that on my 496. I had to buy a bilge pump to suck from a bucket, to pump into the ears. After that no issues.

Went to sea strainer and had hose connection feed in. One of the best investments I did to the boat.

The rubber impeller spinning in the housing lowers atmospheric pressure within the pump cavity and the pressure differential causes water to flow into the cavity. To be technical. Suction is completely different. I was actually awake during hydraulics 😂

I wasn't, I like suction, it's fun to say😁

The lines cannot be 'primed' unless you have some sort of bleed just before the inlet of the pump. An impeller pump is a PD pump or Positive displacement. The inlet is 'sealed' from the outlet so you cannot run water into the inlet due to the inlet being 'airlocked'.

This of course assumes that the impeller and housing are in good condition.

Also to answer the question about suction: Yes PD pumps do produce suction or a bravo style impeller would never see water.

I 100% agree with you.....i only did that to get the liquid up to the impeller quicker during cranking so it wasn't left up to the impeller to try and pull out of the drum it was in. When the boats in the water, the water line is above the seawater pump and when you start to crank the water will force its way in easier...even though the impeller is trying to suck it in at the same time. By using the bilge pump on startup i figure the impeller is working less hard and is less likely to get damaged trying to pull liquid into itself. Im probably overthinking it but i hate contorting myself to get the seapump out to change impellers so anything i can do to prolong its life between changes is good for my back! :D

Actually...this whole conversation reminded me of something. About 20 some odd years ago when i started working for the pump company i'm at right now...we tested a merc seawater pump just to get an idea of our mag-drive system could be used on a rubber vein impeller style pump. If memory serves me well i think we either had a 1.5 or a 2hp electric single phase 220v motor hooked to it. It didn't have enough starting torque to get it moving from a dead stop! Once it was given some help by hand it took off. Those pumps can do some decent volume of liquid and they generate some impressive pressure! Again if my memory is correct it did somewhere in the neighborhood of about 85-90' of head height which translates to just under 40psi! Im not sure how good the impeller was in the pump we tested so a new impeller and new housing may generate even more pressures!

OMG!!!! ROTFLMAO!!!

Need to watch more South Park.