Raw water pump in OD....needed?

[FreeBeeTony]

This question came up in another thread........being I have an engine mounted raw water pump......is the raw water pump still needed in the OD? I was under the impression it did provide somw cooling to the OD.....

This is a quote from ziggy......

"just a question. i didn't think the sea water pump or any of the cooling system kept the gears cool. i thought it was strictly convection via the drive being in the water. or a aftermarket drive shower... am i missing something?"

 

[ErieRon]

Re: Raw water pump in OD....needed?

Tony; Good question. I just looked at mine and a cutaway of a 1 drive. It sure doesn't look like it would provide any significant cooling to anything critical. The water path actually seems isolated from the gear sets. I guess it would provide a little cooling at the top end, but it can't be much. If it were me, I'd leave it in and functioning...but that's just me

 

[FreeBeeTony]

Re: Raw water pump in OD....needed?

I plan on leaving it in........I thought I was told it should be there even though it's not used for the engine.

 

[ErieRon]

Re: Raw water pump in OD....needed?

Can't hurt anything, and you wouldn't have anyone to blame if it went south without it...

 

[ziggy]

Re: Raw water pump in OD....needed?

i only have more questions...

do you have a separate sea water strainer pickup?

or does the water inlet come from the normal inlet on the drive?

if the water comes from the drive inlet and is routed normal up to the engine driven sea water pump. i could see the water pump in the drive as being relevant. i'd assume the route water would take then would be in the drive, through the alhpa1 water pump feeding up to the belt driven pump. could be i suppose. i see the belt driven pump offers much more flow.
if you have the separate inlet. mounted to the boat. not via the drive. what would the purpose of the water pump in the drive serve? the route the water would take then would be from the strainer in the water up to the belt driven pump.

to me i guess the question would be. are the two pumps in series and working together, or is the belt driven pump stand alone? if stand alone, where would the water picked up by the drive route to?

i don't know the flow for a belt driven sea water pump, just asking questions....

fwiw, looks like white mineral deposits on your drive in your other thread. though i suppose it could be corrosion from your salt pond. but my drive gets white like that too. i assume from being hot and evaporating water off the drive while on plane, leaving the white minerals behind... lime away takes them off if that's what it is... point is though. the drive gets hot enough to evaporate the water off... this i think is normal operating as i see many drives with the white chalky stuff (minerals) on them.. + the invention of the drive shower to keep the drive cool... who knows if a shower is necessary. mercruiser must not or they'd offer them from the oem...

 

[FreeBeeTony]

Re: Raw water pump in OD....needed?

ziggy.....

The 2 pumps are entirly seperate.......in fact the water hose that usually connects the OD to the transom shield is cut and just pumps back into the water.......the inlet to the transom is sealed.

 

[TilliamWe]

Re: Raw water pump in OD....needed?

I was under the impression it did provide somw cooling to the OD.....

This is a quote from ziggy......

"just a question. i didn't think the sea water pump or any of the cooling system kept the gears cool. i thought it was strictly convection via the drive being in the water. or a aftermarket drive shower... am i missing something?"

You are wrong, ziggy is right.

On a Bravo series drive and on all current VP drives, which have engine mounted raw water pumps, there is NO pump mechanism in the drive at all. The raw water pump in the outdrive does not provide ANY cooling for the gears, at all.

 

[Bondo]

Re: Raw water pump in OD....needed?

Ayuh,... OK, I wandered over from your hinge pin thread Tony,...
And here's My thoughts...

The entire outdrive Casting acts as a heatsink,...
Pumping water up thru the middle of it probably don't really cool things a whole lot,...But it don't Hurt either...
The water spraying around the transom probably does slightly More good...
Although any little bit of Extra cooling is Always welcome...
A Drive Shower would no doubt do More..

As for Not replacing it,...
The lower housing of the pump supports the vertical shaft,+ holds the Seal...
So,.. You can't really leave it totally out...
If you reinstalled a rebuilt pump,+ left the vertical water Tube off it,...
It would probably do the Most cooling possible, by spraying the Inside of the casting, cooling it slightly...
But,...
Then it'll be spraying water, Opposite the direction of the exhaust flow...

So,....
At the very Least,...
Put it back together with the junk impeller in it,+ Atleast the seal will be In-place...
Or,...
Put it back together the way you had it....
Or,...
Put it back together the Right way,...
Then figure out how to use that unused water to run a Drive Shower....

I know that's a pretty wishy-washy opinion, but I've never had occasion to try any of the alternatives...

 

[FreeBeeTony]

Re: Raw water pump in OD....needed?

Thanks bondo.........gonna replace the impeller anyway and put it back together......can't hurt anything.......

 

[rodbolt]

Re: Raw water pump in OD....needed?

just be aware if the impeller is in the OD then when flushing on land you MUST provide water to BOTH pumps or bad things happen.

 

[FreeBeeTony]

Re: Raw water pump in OD....needed?

Got that covered Rodbolt......have a 'Y' connection on my hose.

Been doing it this way for a few years now.......just was n't sure if the pump in the OD was needed......I'm gonna leave it in there.