Water pump/Impeller on 1981 70hp Johnson

[Sliver]

Greetings,

I am about to attack this project and my manual does not describe the job fully. With the help of this great site I have most of my questions answered, but I do have a couple left.
1) Does the lower unit need to be drained? I just changed the fluid last fall.
2) It sounds like the worst part is disconnecting the shift linkage at the top. My question is does the linkage come off at the bottom too, or do you have to drop the lower unit low enough to slide the whole linkage out?
3) Any other things to watch out for?

Thanks to all who participate here, especially Tashasdaddy. I would never have thought to look for a # stamp on the ends of the orifices (jets) for my carbs.

 

[Gary H NC]

Re: Water pump/Impeller on 1981 70hp Johnson

Draining the gear lube is not needed.The shift rod comes out with the lower so you will need the motor tilted to allow room.
DO NOT turn the shift rod once its apart.It screws in or out of the gear case to adjust height and you don't want to change that.
Remember to lube the splines on the drive shaft with a light coat of grease and a little gear lube on the impeller when you put it in is a good idea...

 

[HighTrim]

Re: Water pump/Impeller on 1981 70hp Johnson

I usually remove the prop as well when dropping the lowers, 1 because they are usually V6's and am usually alone and dont want to damage the prop, and 2 so that I can clean up any old fishing line that has wrapped around the prop shaft, and to grease the splines of the propshaft with marine grease.

I would also flush the cooling system with compressed air or the garden hose as well while the lower unit is down. Be careful lining up the grommet on the impeller housing, as they are prone to get jammed in the housing when re installing the lu. These videos may be of some help. Good luck.

http://www.meegsonline.com/tmd/waterpump.wmv

www.themarinedoctor.com/videos/removecase.wmv

www.themarinedoctor.com/waterpump.wmv

 

[5150abf]

Re: Water pump/Impeller on 1981 70hp Johnson

If you haven't gotten it already, yes, change the lower oil, it is $5, a new lower is $1200, it is the easiest way to see if you have a leak.

I just had mine off(81 50 Rude) monday to fix a seal.
Pull the starter, put the boat in forward gear and remove the shift bolt with a 1/4 ratchet, long extension and swivel, pull the lower bolts(there are 6)
and drop the lower.
When you get to the pump there really is nothing special, make sure the key is in and as stated put some oil or grease on the new impeller,the top of the drive shaft and especially the gasket on top the water pump, it will help it slide onto the pick up tube.
Make sure you pull up on the shift rod to put it into forward and work the lower back on making sure you line up the pick up tube, you will probly have to spin the prop shaft to line up the drive shaft.
Once it is up and you have abolt secureing it here is a trick I found that makes the shift rod a breeze to hook back up.
Between the lower and mid at the front of the engine is a small break in the housing where you can get a pair of needle nose vise grips on the shift shaft to move it up/down/turn it, Makes it alot easier to hook up.
Also if you can get a partner to wiggle the shifter that helps too.

Hope that helps and let us know how it goes.

 

[Sliver]

Re: Water pump/Impeller on 1981 70hp Johnson

Thanks for the advice guys, I will let you know how it goes.

 

[Sliver]

Re: Water pump/Impeller on 1981 70hp Johnson

Got the LU down no problem thanks to good advice here. Unfortunately the repair kit I got here on I-boats is the wrong one. The impeller has a recess for a lobe rather than a slot for a key like mine has. So it looks like I'll be waiting for the right parts. After the LU was down a small (3/4") or so O-ring fell out. Am I right that it goes on the driveshaft? TIA

 

[HighTrim]

Re: Water pump/Impeller on 1981 70hp Johnson

You may have a different year lower unit than power head.

There is an o ring at the top of the drive shaft, dont forget this during reinstallation, along with marine grease on the splines.

 

[Sliver]

Re: Water pump/Impeller on 1981 70hp Johnson

Interesting, however the diagram for 1981 shows a slot and key which is what I have. The new one I got which is Mallory 9-48213 (supposedly for an 81) has a sort of teardrop recess in the impeller. Also, the plate that came in my kit has a smaller slot opening than the one that is on the motor now. Unfortunately Iboats returns is not open till Tuesday. Thanks for input.

 

[Sliver]

Re: Water pump/Impeller on 1981 70hp Johnson

OK, now I am confused. I ordered for an 81 which by serial # J70ELCIM is what I have. The impeller page here on iboats for 79-84 shows a "wedge" key and the impeller for 74-78 shows a slot key. Is it likely that they still had some slot type water pumps when they built this one? Is there a way of telling the year of my LU? Thanks,

 

[HighTrim]

Re: Water pump/Impeller on 1981 70hp Johnson

It is hard to determine the exact year of a lu, although we could easily tell you a year 'range', which you already know. That is all that you will need for ordering parts. Just be sure to remember that in the future when ordering, not really a big deal. I have ordered water pumps a few times only to drop it later and realize that the lu has been swapped with a different style.

 

[Sliver]

Re: Water pump/Impeller on 1981 70hp Johnson

I think I know the answer but I am curious. I received the correct impeller in this kit but would like to know why the base plate has such a different size hole. I assume I should use the one that's on the pump now. Thanks.