View Full Version : Need Help With My Raw Water Pump

04-20-2008, 09:28 PM
I need some help with a non-MC boat. I have a 96 Maxum 210SS V-drive (yes, Maxum actually made v-drives for a couple of years) with a 5.7L Mercruiser Black Scorpion engine in it. I was going through the process of changing the impeller on it and got going too fast. I took the water pump off and put the new impeller in and realized that I didn't pay a lot of attention when I took the pump out of the boat. Now I'm confused as to exactly how it goes back in. The way I thought it was supposed to go back in doesn't seem to work because when I hook up the hoses to the pump the pump is too low to fit in the bracket. So my question is which hose, the one on the left or the one on the right of the pictures below goes onto which connection of the pump?

The pump housing has "LH Out" under one connection and "RH Out" under the other connection. The pump is part #46-807151 and says SAE PF-GF and LH ROT (left hand rotation I assume). I appreciate any help you can give your non-MC brethren.


04-20-2008, 10:08 PM
Have no idea bro but it would seem to me the type would be reading normal (not upside down when installed) That the LH out would go to the outside hose and RH out would go to the hose going under the motor. My :2cents:......Right now I'm switching motors and TAKE PICS of everything before takeoff!

Switch your mounting around till you find if it fits right.

04-20-2008, 10:29 PM
That's the way that makes sense to me also but when I clamp the two hoses onto the pump in that orientation, the pump is sitting down too low to even get close to the mounting bracket. The hose on the left is just a couple inches long and goes into something that i can't see (under the engine) that keeps the hose from flexing or bending any. The hose on the right can be moved around pretty easily. It just doesn't make a lot of sense right now...

Also, if I got the hoses on the wrong ports of the pump, would it really make a difference? When looking at the pump and picturing how the water would flow it really doesnt seem like it would matter but I'm not sure and don't want to fry my engine.

Good advice on taking pictures, I guess my camera's a little more reliable than my photographic memory.

04-20-2008, 10:41 PM
It would make a big difference which way the hoses are attached! ones "IN coming" and ones "OUT going"! The pump draws water one way!

That pump run off that belt I assume? any brand name on the pump?

Carbon Dreams
04-20-2008, 10:54 PM
Trace the Intake line from the water intake on the bottom of the boat. That's the IN... If you want pour some water down the line to see if it comes out the intake. Hook up accordingly.

Edit: Or, trace the line going to the engine block, that's your out.

04-20-2008, 11:08 PM
Carbon, I understand what you're saying but both ports on the pump say OUT. One says LH OUT and the other says RH OUT. So which one of the ports to the pump is actually the output?

Fintek, I know what you're saying but when you look at how the pump's designed it just looks like it doesn't matter. It merely sucks water into one hole and pushes it around the chamber and then spits it out the other hole. It seems like if you put the water supply on the wrong port it would still suck from wherever the supply is. Don't get me wrong, I'm not gonna try hooking it up backwards. I'm just making an observation. Yeah, the pump runs off the belt that you see hanging and no it doesn't have a brand name.


04-21-2008, 10:15 AM
Fintek, I did a little research and now understand why it makes a difference. My concept had a major flaw, I was thinking of a perfectly round housing where the blades all look the same relative to each other at any given time. This type of pump uses the flexion of the blades to create a vaccuum. The blade gets compressed at the top and as it goes by the inlet it lengthens to its greatest length creating a vaccuum because the volume has changed. This sucks water into that chamber. As it rotates around the blade begins getting compressed again and then passes the outlet and discharges the water.

So you're exactly right, it makes a big difference and now I completely understand why. Question remains, how do I need to hook this sucker up.

04-21-2008, 11:19 AM
I'm going to assume that pump is used on both right/rotation engines and left/rotation engines (like bigger boats with twin engines) or perhaps Fords which are left-rotation.

Your 5.7L (chevy) should be a right rotation engine (bump starter and watch what way it rotates from a front view) This would most likely mean "RH out" in the discharge side and "LF out" is the suction side.

This is purely a guess on my part. Are there any rust-marks where you could tell how it was bolted-up before?

04-21-2008, 11:33 AM
You need to determine which way the pump rotates when it is in place on the brackets. Then spin it by hand and verify that it draws on the side you connect to the raw water line.

04-21-2008, 12:18 PM
The pump says "LH ROT" on it with an arrow pointing in a counter-clockwise rotation. Any rust marks that may have been on the bracket are gone now. Every time I take off a part that is rusted I try to wire brush as much rust off as possible and paint it with some Mercruiser spray paint. As you can see from the pics I seem to be fighting a losing battle.

Also, does anybody know what the fuel filter looking thing to the right of the fuel water seperator is? Do boats have both a fuel filter and a fuel water seperator?? If it is a fuel filter, how often do I need to change it?