1979 1/2 merc 115 water pump install tips

[Georgesalmon]

When I removed my water pump (which was working) the impellor looked pretty good but the top of the bottom section of the pump below the SS plate under the impellor was melted. So, I'm glad I'm not wasting my time.

Got my new water pump and ready to install. I have a couple of quesions. The upper lower unit seal is the bottom of the water pump. I can see the bearing and it looks good. There were two shims on the top of the bearing, ,015 and .020. Do these need to be replaced as is or is there some kind of measurment to determine if needed? I assume that they must space the pump above the bearing to some specific tolerance? Also, should I grease the top of the bearing and the seal with merc 2-4-? w/teflon or lower unit oil, or nothing?

Should I put some vasoline or something else on the impellor during install to prevent a dry start?

At the forward end of the lower unit just behind the frone attaching stud there is a plastic looking nut with about an inch of small black hose tie wrapped onto a hose fitting. I can't find anything above it in the motor that it would attach to. The black hose is about the size of speedometer hose. Was this an early attempt at a speedo pickup at the motor? Do I need to worry about it?

Thank you.

 

[Moody Blue]

Re: 1979 1/2 merc 115 water pump install tips

Servicing the waterpump is never a waste of time. The impellers will often look good but they take on a "set" and become hard and will loose efficiency over time. I'm assuming you're replacing the upper housing as well, because the S/S cup insert usually gets groves worn in them on the top surface, again reducing efficiency of the pump.

The waterpump base should have two seals in it, one to seal the water OUT of the lower unit, and one to seal the oil IN the lower unit. There is also an o-ring seal around the outer body to seal the housing to the casting. The shims are important as they determine the meshing of the pinion gear with the fwd and reverse gear. There is a specific procedure to follow but I am not familiar enough with it to describe it to you. I'm sure someone will come along with more details for you. If not, I'll copy the pages out of the manual and post it here.

Always lube the seals before installation. Apply lube to the driveshaft also before sliding the waterpump base with seals down over the shaft. Use caution as the seals slide down the upper driveshaft splines and past the notch for the impeller key, you don't want to nick the seals. I use a silicone type lube but you can use oil, vaseline, thin film of grease etc. Lube the inside of the S/S impeller cup and the S/S wear plate with vaseline or dishsoap so that the impeller does not stick to the mating surfaces. Makes inserting the impeller into the cup much easier also.

That short tube section you describe is the speedo pickup as you suspected. If you don't want to use it just leave it or remove it as I did to mine and plug the port with a 1/8" NPT plug.

 

[Georgesalmon]

Re: 1979 1/2 merc 115 water pump install tips

thank you for the reply. Good info. I miss spoke above about already having the water pump. My water pump kit, top and bottom will be here today along with a seloc manual. It was in WI yesterday by UPS. If the manual has the information you mentioned you won't need to copy yours though I thank you for the offer. The top section does have the grooves you described in it.