1971 Merc 7.5 Impeller Question

[brian_in_pa]

I recently bought a 1971 Mercury 7.5 HP motor, and when I started it up, there was no water coming out the tell tale, so I pulled the lower unit off to take a look. Some history on the motor is that it hasn't been used for 4 years, but it started on the 5th pull.

This is my first outboard, so I have never had one apart before, but I know how to find my way through a tool box, and how something should work, but I am not a professional. When I pulled the top off of the water pump, I noticed that the impeller is not centered in the water pump housing: it is offset which causes the blades to be curled. Is this normal?

Thanks in advance,
Brian

 

[8075mercury]

Re: 1971 Merc 7.5 Impeller Question

Impeller pattern is normal, that is actually how it pumps. It takes water in the larger area and pushes it to the smaller area. Since the water has an outlet, it flows out the pump and up the tube. (Well hopefully, when all is working well!)
Suggest you buy a Mercury service manual or Seloc (I like Seloc) off ebay or from Mercury direct. I suggest putting in a new impeller every couple of years.

Good luck, great motors ! Check electrical wires for deterioration and watch the drive shaft (if original) for rusting.

 

[brian_in_pa]

Re: 1971 Merc 7.5 Impeller Question

I found the rust, and the dirt, and the grit when I pulled the lower unit off. After reading some of the other posts here I was prepared for the sticking lower unit, so I wasn't too surprised with what I saw. I just wasn't sure about the the curling of the impeller blades.

The more I worked at it, I began to realize the impeller was rusted to the shaft. It took some work to get the impeller oof, so now it looks like the whole water pump. While I am at it, I will take your advise and get the manual.

 

[brian_in_pa]

Re: 1971 Merc 7.5 Impeller Question

As I noted in the previous post, when I remved the lower end, I found a lot of corrosion on the drive shaft. THere was so much corrosion that the impeller was corroded to the shaft. I wasted several hiurs trying to remove the impeller without damaging anything else, but the hack saw came out and I had to cut the waterpump base so that I could pry up on the insert and impeller. I was able to get everything opff, and I bouth an entire waterpump kit and a Seloc manual. I am ready to put this thing back together, but I am concerned with the number of parts that came with the pump kit. The diagrams show where a part goes, and they are even using the name of the part, but the diagrams do not clearly show what the part appear like. Does anyone have photos?