How many water pumps?

[Tahoe 55]

I'm corn-fused....
As I've said before, I'm new to boats... My question is, how many water pumps are involved in my raw water cooled 5.0 MPI/Alpha? I know there's a belt driven raw water pump on the bottom left of the engine. Plus a circulating pump (like an automotive engine water pump) but now I think I understand that there's another water pump in the outdrive? Is this correct? My owners manual only talks about the raw water pump and to check it every 300 hours?? Is this all I need to worry about?

Thanks

 

[Don S]

Re: How many water pumps?

The Alpha's do come with pumps in them. When an engine has an engine mounted pump, the hose going from the outdrive to the transom shield is cut and plugged. This way the water from the drive pump is used to cool the outdrive only.

 

[Fishermark]

Re: How many water pumps?

Don, is it common to actually plug" the end? Wouldn't that cause the water to "deadhead?" Unless the plugging you are refering to is at the transom itself?

In other words, if I understand correctly, the hose is simply cut, and the transom is blocked off. That allows the water to flow out of the hose and splash against the transom.

On a side note - is it not possible for one to remove the guts from the water pump in the leg and simply draw the water up and through like a Bravo?

For what it is worth, on my setup, I have a through hull pick up for the engine mounted pump, and I have the pump from the lower unit flow through and then straight out the back of the transom. I've always wanted to divert it through a "Y" valve and have it either go out the back, or through a hose for a covenient wash down feature. A project for another day.

 

[Tahoe 55]

Re: How many water pumps?

Hmmm...
If the hoes it cut and plugged, where does that water cycle back out of the system? Does it cycle around in the outdrive and then get picked up by the engine mounted pump? Just having trouble picturing what's taking place here.
Thanks

 

[Fishermark]

Re: How many water pumps?

Your engine mounted raw water pump probably has a thru hull fitting. Check the routing of the hose going into the back of the pump. Is it coming from your transom (and outdrive) or is it leading to the bottom of the hull. (Hopefully through a shut off valve!)

 

[willis3368]

Re: How many water pumps?

You need to check that water pump atleast anually. Every 300 hours that could be 6 years. Rubber or the neoprean that the impeller is made of will dry rot or the vains will become permanetly curled, this will render the pump usless.

For a hundred so dollers it cost to get it done or the 30 to 60 bucks the kit cost to do it yourself every year is small change compared to what it cost to replace or rebuild your motor!!!



No Water No Engine!!!

 

[Tahoe 55]

Re: How many water pumps?

My water pick-up its through the outdrive and flows out the bottom sides of the gimbal ring with exhaust.

 

[Tahoe 55]

Re: How many water pumps?

Willis, you're talking about the engine mounted raw water pump?

 

[Fishermark]

Re: How many water pumps?

And you're sure you have an Alpha?

 

[Tahoe 55]

Re: How many water pumps?

Yes

 

[tommays]

Re: How many water pumps?

I am a bit confussed as and alpha is NOT setup to have water sucked through it to supply a motor mounted pump

 

[willis3368]

Re: How many water pumps?

Any water pump, the longer they sit in the housing the worse it is for the impeller.

The shaft the impeller is on is offset in the housing causing the veins to bend over. If they stay in that position for a long period of time they will not straiten back out. This will cause the pump to spin the water in the housing insted of pumping it through the engine.

 

[Tahoe 55]

Re: How many water pumps?

I am a bit confussed as and alpha is NOT setup to have water sucked through it to supply a motor mounted pump

Now I'm confused or maybe I'm just still confused. It's defiantly and Alpha I 2nd gen bolted to a "07 Merc 5.0 MPI (brand new boat). I've put muffs on the water pick-ups on each side of the outdrive (right behind the prop). It flowed in and kept the engine cool...
My owners manual and dealer confirms the water pick-up in the outdrive.
There's no question that this is an Alpha.

 

[QC]

Re: How many water pumps?

Then are you sure you have a belt driven RAW water pump? With a factory installed Alpha that would be very strange . . Also you said "left side of engine". Let's use Port and Starboard and get this correct. If it is on the Port side it is not a water pump . . . At least not one I have ever seen.

FWIW, the raw water pump impellers of either type need changing frequently. Most say two years. I just had a three year old, belt driven one go and it was absolutely destroyed and I ran the season with it until the last trip. So they can fail after sitting OR after use . . .

 

[Tahoe 55]

Re: How many water pumps?

Maybe I don't have a belt driven RAW water pump...
When I said left, I meant Starboard side.
I'll check for this pump and report back later.
Thanks for the help so far.

I was just reading on how to change the water pump in a Alpha drive and it sounds very complicated... Is this true?

 

[Fishermark]

Re: How many water pumps?

Here's a picture of my engine. Note under the alternator, on the starboard side, there is an engine mounted raw water pump.

On the port side is the power steering pump.

 

[Tahoe 55]

Re: How many water pumps?

From the image in my head... That's the way mine looks too. I'll see if I can find a pic.

 

[Tahoe 55]

Re: How many water pumps?

This is my engine

 

[QC]

Re: How many water pumps?

I think that is your engine as it is shown on Merc's website for use with a Bravo . . . We need to see your engine. Again, it would be very odd for a manufacturer to use an Alpha and also go to the extra expense of an engine mounted raw water pump . . . Maybe, could be, but unlikely . . .

 

[Don S]

Re: How many water pumps?

Mercruiser would never put 2 raw water pumps inline like that. So my guess is you have an Alpha I Gen II drive, and really don't have the engine driven pump. Or you have a Bravo I drive (Hear the word ONE in both of them) and have the engine driven pump, and no pump in the outdrive because it's a Bravo I.

I've marked up your picture to show what pulley is what.