1975 Merc 7.5

[love1u0]

Hi,
Picked up a 7.5 Serial #4249088 for 200 bucks. I put it in a tub and it ran great but it was not peeing any water out. I pulled the lower unit off and checked the impeller. It needs replaced, but it wasnt bad enough to not be pumping water.

The only thing I could see was that the plastic water tube fits real loose over the copper pickup tube going to the power head....could that be my problem, what else can I check?

Thanks

 

[saltyfries]

Re: 1975 Merc 7.5

I have a 69 7.5 and I have read that these engines didn't change much through the '70's at least. I had the same problem with mine.

The plastic guide tube with the beveled cut is just to help guide the water uptake tube into the rubber seal of the water pump during installation. It is supposed to be loose. After dropping the gearbox and connecting a hose directly to the water uptake tube in the lower leg, I discovered that most of the cooling water exits two little holes in the bottom of the engine block and drains into the lower leg. The telltale is just that: a visual aid to let you know the pump is pumping. Turns out mine, which I found right next to the flush port on the right side of the lower leg and just above the lower edge of the cowling, was just plugged up. I took a small piece of wire and with the hose running, I rodded it out. Now it flows well.

 

[love1u0]

Re: 1975 Merc 7.5

Hey thanks,
I pulled the screw for the flush and sure enough it is plugged up. I imagine the rest of the cooling passage is the same. I will get some wire and roto-root it out.