2000 340DA 7.4L impeller change tips

jim_m5

Member
Aug 19, 2008
275
Woodstock, GA
Boat Info
340 Sundancer 2000
Engines
7.4L 310hp V-Drives
I am a bit handier than Captain Hook... but want to take a stab a saving some$. Does anyone have advise, tips, techniques, pics for changing these impellers? I had it done last July so I am OK for awhile. But I want to do it myself next time and thought I would start my education. Appreciate any guidance?
 
I have done it on my 300 DA... But this 340 looks really tight... I would appreciate some words of wisdom too... I plan on changing my impellers this spring... BTW anyone have a part number for the impeller on a 2001 340 7.4 MPI???
 
You don't need to change them until they fail.



Ok, just kidding, I changed them on mine when I had it. It is pretty tight, I had to lay on the top of the engines, and reach down to the bottom where the pump is. You may want to get an old pillow to make this a little more comfortable. I don't recall all the steps, but since nobody else replied yet, this will give you an idea.

0) Close seacocks
1) Remove the serpentine belt (easy, loosen lock nut on tension pully)
2) Remove a few bolts holding water pump bracket.
3) Remove a few bolts holding bracket to pump.
4) Loosen two hose clamps holding water hoses, and remove hoses
(remember which goes where)
At this point you can remove the pump and take it topside.
5) Disassemble water pump (again very easy, just a few bolts)
6) Remove old impeller (check that you have all the pieces, otherwise go find them)
7) Soap up the new impeller and twist it into place (note spin direction)
8) Reassemble the pump (impeller should come with new o-ring)
9) Reconnect the hoses
10) Reinstall the pump and bracket
11) Reinstall and tension the belt
12) Open Seacocks

As I said this is all from memory so I may have missed something, but I did mine, after one of them failed :smt013. I would plan on about an hour or so each for the first time. I think the hardest part was reaching down there and working upside down.
 
Well, it was shortly after I got the boat. Didn't know any better then...

I changed them on the 480 before we took it home.
 
Thanks... I have it on my todo list... Just have reassemble my Westebeke, replace all the plugs, change the transmission fluid, change the fuel filters, put the Genny back in, put the exhuast back together, then I can change the impellers... Then, I can pull the boat to paint the bottom and wax... Hope to be done by July...



You don't need to change them until they fail.

Ok, just kidding, I changed them on mine when I had it. It is pretty tight, I had to lay on the top of the engines, and reach down to the bottom where the pump is. You may want to get an old pillow to make this a little more comfortable. I don't recall all the steps, but since nobody else replied yet, this will give you an idea.

0) Close seacocks
1) Remove the serpentine belt (easy, loosen lock nut on tension pully)
2) Remove a few bolts holding water pump bracket.
3) Remove a few bolts holding bracket to pump.
4) Loosen two hose clamps holding water hoses, and remove hoses
(remember which goes where)
At this point you can remove the pump and take it topside.
5) Disassemble water pump (again very easy, just a few bolts)
6) Remove old impeller (check that you have all the pieces, otherwise go find them)
7) Soap up the new impeller and twist it into place (note spin direction)
8) Reassemble the pump (impeller should come with new o-ring)
9) Reconnect the hoses
10) Reinstall the pump and bracket
11) Reinstall and tension the belt
12) Open Seacocks

As I said this is all from memory so I may have missed something, but I did mine, after one of them failed :smt013. I would plan on about an hour or so each for the first time. I think the hardest part was reaching down there and working upside down.
 
I changed my out on the starboard and had no problems. I also asked a mechanic if I needed to pull the bearings out to check them out and he said "No" unless you have a trace of rust from the bearings or bearing roughness. One other thing on replacing the impellars. If you have an impellar with parts of the blade missing go searching up stream for the pieces. If you have a water flow restricter in line with the pump, it will be there.

Good luck
 
You don't need to change them until they fail.



Ok, just kidding, I changed them on mine when I had it. It is pretty tight, I had to lay on the top of the engines, and reach down to the bottom where the pump is. You may want to get an old pillow to make this a little more comfortable. I don't recall all the steps, but since nobody else replied yet, this will give you an idea.

0) Close seacocks
1) Remove the serpentine belt (easy, loosen lock nut on tension pully)
2) Remove a few bolts holding water pump bracket.
3) Remove a few bolts holding bracket to pump.
4) Loosen two hose clamps holding water hoses, and remove hoses
(remember which goes where)
At this point you can remove the pump and take it topside.
5) Disassemble water pump (again very easy, just a few bolts)
6) Remove old impeller (check that you have all the pieces, otherwise go find them)
7) Soap up the new impeller and twist it into place (note spin direction)
8) Reassemble the pump (impeller should come with new o-ring)
9) Reconnect the hoses
10) Reinstall the pump and bracket
11) Reinstall and tension the belt
12) Open Seacocks

As I said this is all from memory so I may have missed something, but I did mine, after one of them failed :smt013. I would plan on about an hour or so each for the first time. I think the hardest part was reaching down there and working upside down.
So, on the 7.4 you actually remove the entire pump and impeller housing rather than just removing the cover on the impeller housing to change it out? Thanks.
 
That is correct. The entire pump housing that contains the impeller, as I recall, is plastic.
 
After I changed the impeller on my generator, I quickly decided that I was not going to do the impellers on my engines - I was sore for two days. It was a royal PIA and I have the 6.2's.....

Good luck!
 
After I changed the impeller on my generator, I quickly decided that I was not going to do the impellers on my engines - I was sore for two days. It was a royal PIA and I have the 6.2's.....

Good luck!
I did my 7.4s and I'll never do them again! What a PITA!!!
 
A few years ago someone posted a play by play on this. Then the next time I was in the bilge I took a look to see how tough it might be. Just getting into position to be able to reach anywhere near the pump was enough to tell me that this was a repair I would pay for, not DIY.
 
I take out back bench so I can pull pin and lift engine cover all the way up and chock it with something. I then remove the two inside exhaust tubes (Log Muffler) so i can stand in there and move around easier. Its a little more work to do this but makes it easier to do anything in engine compartment. Then follow above directions.
 
You don't need to change them until they fail.



Ok, just kidding, I changed them on mine when I had it. It is pretty tight, I had to lay on the top of the engines, and reach down to the bottom where the pump is. You may want to get an old pillow to make this a little more comfortable. I don't recall all the steps, but since nobody else replied yet, this will give you an idea.

0) Close seacocks
1) Remove the serpentine belt (easy, loosen lock nut on tension pully)
2) Remove a few bolts holding water pump bracket.
3) Remove a few bolts holding bracket to pump.
4) Loosen two hose clamps holding water hoses, and remove hoses
(remember which goes where)
At this point you can remove the pump and take it topside.
5) Disassemble water pump (again very easy, just a few bolts)
6) Remove old impeller (check that you have all the pieces, otherwise go find them)
7) Soap up the new impeller and twist it into place (note spin direction)
8) Reassemble the pump (impeller should come with new o-ring)
9) Reconnect the hoses
10) Reinstall the pump and bracket
11) Reinstall and tension the belt
12) Open Seacocks

As I said this is all from memory so I may have missed something, but I did mine, after one of them failed :smt013. I would plan on about an hour or so each for the first time. I think the hardest part was reaching down there and working upside down.
 
Its a lot easier if you take out the exhuast system and the mounting bracket then you can get int here and work. Tried to do it first without removal and they are just to far down under...
 
Tip -- Disconnect the hose at the Trans-Cooler first, then when you remove the pump, just slide the pump out with the hose attached.. Then remove the hose at the pump.. When installing, attach the hoses first, then attach the pump.

Also, spend the money and buy the whole pump. Then buy an impeller for the old pump and keep it as a spare.
 
Make sure you know what hose go where on the pump. I put a tie strap on one hose and on pump for that hose. Put lines on the two parts of the pump before you take apart. I also have spare pump and rotate the pumps. Do one put in spare. Rebuild removed and next time I want to be tortured I do the other pump. I have had the seals fail in two pumps. Changed out to spare and kept going.
 

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