Mercury 700 Thunderbolt Impeller/Water pump help

JLCollins005

Cadet
Joined
Sep 4, 2017
Messages
6
I recently acquired a boat that had this motor and hadn't been in the water since 2004, I believe the boat is a 77 and the motor is a 78. To my surprise the merc looks great and well taken care of and started up almost instantly without issue, and that is when I noticed it wasn't discharging water from the tell tale. After doing a bit of research I decided to move forward with removing the lower unit and checking the impeller, which was toast it came out in pieces but everything looked good aside from that.

I got it back together and it now looks like it is moving water up but its around the exhaust area and still not coming out of the tell tale, I have read and it sounds like the water tube isn't line up correctly or there might be a blockage. I'm wondering if anyone has any tips on how to get the tube lined up correctly?

Thanks,
 

Mercurylips

Petty Officer 2nd Class
Joined
Sep 23, 2015
Messages
189
Very simply, get help. Sometimes you need three hands. When you get the copper tube close you will need to move it a little to get it in the tapered hole in the top of the pump housing. Make sure you have enough light to see what is going on. When it is back on sufficiently to run it on muffs, do so and see if you succeeded. Then.....check that the gear sequence is correct.
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
When you say water does come out of "the exhaust area," do you mean the through-hub, or the little vents on the back of the leg at the top, just under the cowling?
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
which was toast it came out in pieces


Chances are that pieces of the impeller have been pumped into the engine.

Need to back flush.

If your motor has a thermostat, remove it, use a garden hose to force water into the thermostat housing.

Then replace the thermostat with new before putting it all back together.


Remove the telltale hose and clean it out too.
 

JLCollins005

Cadet
Joined
Sep 4, 2017
Messages
6
Thanks for the responses.

Currently the tube is attached to the actual water pump housing are you suggesting I disconnect from that and insert into the hole at the top of the shaft first? I'd have to check again but it looked like the water was coming out near the top/back of the motor not the front exhaust area.

Thanks for the help
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
water tube should be attached to the powerhead/adaptor plate.

It gets inserted into the water pump as gearcase is slide into place.
 

Mercurylips

Petty Officer 2nd Class
Joined
Sep 23, 2015
Messages
189
Thanks for the responses.

Currently the tube is attached to the actual water pump housing are you suggesting I disconnect from that and insert into the hole at the top of the shaft first? I'd have to check again but it looked like the water was coming out near the top/back of the motor not the front exhaust area.

Thanks for the help

​The tube is was posting about is the main water supply tube about the size of a small finger and is attached to the motor above the lower unit. If that tube is not installed correctly and in place before you put the lower back on, please let us know so we can help sufficiently.
 

JLCollins005

Cadet
Joined
Sep 4, 2017
Messages
6
When I pulled the lower unit off the tube was attached to the water pump housing, I will be removing the lower unit again this evening and can post pictures then.

I appreciate all the help
 

JLCollins005

Cadet
Joined
Sep 4, 2017
Messages
6
No Title

Hi everyone,

I was able to get out and work on the boat today and took some pictures, I just want to make sure I fully understand before my next attempt at putting it back together.

I've uploaded two pictures, the water tube can be pulled off so to be clear you are saying push the tube in first and then as I'm putting the lower unit back line it up on the water pump?

Thanks again.
 

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GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Pull the water tube out of the pump housing and stick the top end into the water tube grommet. Trying to stab the water and drive at the same time is nearly impossible. It's much easier to use a thin screwdriver to line up the tube with the water pump as the lower unit is raised.
 

Mercurylips

Petty Officer 2nd Class
Joined
Sep 23, 2015
Messages
189
Hi everyone,

I was able to get out and work on the boat today and took some pictures, I just want to make sure I fully understand before my next attempt at putting it back together.

I've uploaded two pictures, the water tube can be pulled off so to be clear you are saying push the tube in first and then as I'm putting the lower unit back line it up on the water pump?

Thanks again.

​I just pulled my lower unit today (similar vintage motor) I will post a photo tomorrow showing how it should look before adding your lower.
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Pull the water tube out of the pump housing and stick the top end into the water tube grommet in the powerhead. Trying to stab the water and drive at the same time is nearly impossible. It's much easier to use a thin screwdriver to line up the tube with the water pump as the lower unit is raised.

Left out a word.
 

1960 Starflite

Petty Officer 1st Class
Joined
Jun 23, 2011
Messages
351
Good advice provided above. FYI: I have a 650 and mud dobbers or some small insect had packed the pee hole with mud. Also, what is the car sitting outside, looks Mid 50's ?
 

Mercurylips

Petty Officer 2nd Class
Joined
Sep 23, 2015
Messages
189
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​I just pulled my lower unit today (similar vintage motor) I will post a photo tomorrow showing how it should look before adding your lower.

​The water supply tube fits up inside of the drive shaft housing next to the main exhaust. The bend in the tube faces that exhaust and will be on the bottom as it is installed. There are two holes up at the top of the drive housing and the tube fits into the hole closest to the main exhaust box. The other hole is for your drive shaft. I have two pictures showing the tube installed. It will only hang below your housing about 1/2 inch when installed. I included another shot with a large screwdriver pointing it out. Sorry I couldn't show the insides of the housing up top. You will need a bright flashlight to help place your water tube.
 
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