Impeller only - or water pump kit? 1978 Johnson 85HP

[AAusbro51]

This is my first post after creeping around the forum for a good month. This is a very very very cool and helpful site you have here. Thank you for all the knowledge and expertise! I am a new (to me) boat owner and I'm just about as green as it gets. Much of my knowledge has come from soaking up different tips and tricks on the sticky posts and general forum posts here.

So... here goes...
I purchased a pontoon with a 1978 Johnson V4 85HP motor.
Compression was 95/96 psi across all 4 cyl.
Changed the lower unit oil.
New plugs.
Added a can of Seafoam treatment to the gas tank and fired it up on muffs.
It ran like a top (so far) & I did the happy happy happy dance!!

The single stream of water coming from under the cowling was strong. I have no idea how old the impeller is - so I have read that that means I should go ahead and replace it. After reading post after post and watching different videos, I pulled the trigger and ordered "an impeller" for my motor. To my dismay, it is literally... just the impeller. I feel I what I should have bought is the entire water pump kit. Much of the forum posts just say 'impeller' - so I didn't even know there was a kit available. I suppose you don't know what you don't know until you've messed up a little.

Two questions:
1. Not knowing the condition of the cup, gaskets, o-rings, impeller... should I have bought the entire water pump kit?
2. If you're opening up those gaskets/seals and such, why would anyone just buy/install JUST the impeller? I can't imagine the scenario - unless you really really only replace that 1 part.

Any other related helpful tips/thoughts for my ole' 1978 juggernaut would be appreciated as well.

Thanks in advance for your help!!

 

[F_R]

One of the beauties of the plastic pump with stainless steel liner is that a new impeller is usually all you need. Unless it has been used in some mighty dirty, gritty, muddy water.

 

[AAusbro51]

Thanks F_R

One last double-check question:
It's common for these water pumps to be opened up and be able to reuse/re-seal the existing gaskets and rings when replacing just the impeller?

I totally understand that if I see something worn or failing that it should be replaced - but folks commonly open them up, replace the impeller, re-seal and move on?

 

[sutor623]

I would get the gasket that goes under the plate and the seal that goes under the waterpump housing. If you can get the waterpump housing off without disturbing the plate underneath the impeller then you may not have to replace that gasket. In either case, certainly replace the seal that goes under the pump housing.

 

[jakedaawg]

As the two above said, just inspect. 99 percent of the time common sense will suffice. Put the new impellar in, seat the cup and housing over it while twisting vertical shaft clockwise, and go boating.

If the cup has grooves in it buy a whole new kit and save the impellar you just bought for the next time.

Just don't listen to the guy on here that tells you to save money by installing the old impellar upside down, haha. I don't think he's been around for awhile though...

 

[David Young]

When I changed the impeller on my 1977 70hp Evinrude, I bought the complete kit. I'm glad I did, the old plate had grooves worn on it because it was the factory original one. I know the 'next several times', I'll just have to replace the impeller

 

[Keyboardman]

No Title

Going to get the entire kit for my 75 Stinger. Might as well do it all while the lower unit's off the engine and apart. David, love your 77 MFG!

 

[David Young]

Your tri-hull looks great too.