I’ve owned the 454/7.4L Mercruiser inboard for many years. And I’ve replaced the seawater pump many, many times. But this last year I had a hell of time getting the new impeller to go into the housing. I finally gave up and took it back to the house.
Here’s what I did to get it to go in easily….I built a jig.
I took a wood 2×4 about 1 ft long and cut a large hole in the center. I used the hole cutter that is found at most hardware stores for cutting a hole in a door for a doorknob. The diameter of this hole is just about the diameter of the smallest dimension of the housing where the impeller fits. I then cut the hole in half along the long dimension of the 2×4. This gave me two pieces of the 2×4 about 1 ft long each with a half-whole cut out.
Then I placed this into a large vise with the two 2×4 sections separated by about 1 inch. After lubricating the impeller with dishwashing soap, I put the impeller in the hole and screwed down the vise until the the impeller was squished a little in the hole. The impeller was in the wood hole with about 1/4 in of the impeller peaking out the top. Do not crank the vise down all the way to make the 2×4 halves come together. You want them to stay separated.
Then I twisted the impeller clockwise using a 3/8 ratchet and a little backup screw to make it mate with the impeller shaft hole. This started the impeller’s fins to collapse like it would in the impeller housing.
Then I cranked down on the vise a little more and twisted the impeller a little more. Again, do not make the 2×4 touch. I continued until the impeller was nearly cranked down to the diameter of the impeller housing. Then I placed the impeller housing down on the impeller ( with the 1/4 in of fins that were peaking out) and twisted until the impeller was just in the housing.
One think I left out. I put under the impeller a large socket and let it rest on the vise, under the impeller.
Now, continue to twist the impeller and hit the 2×4’s gently with a hammer. The 2×4’s will slip downward in the vise, the socket will hold up the impeller, and you will continue to twist and press the impeller into the housing. Repeat the process and it will seat far enough into the housing that pressing it the rest of the way, while twistng, is easy.
doorknob hole cutter
impeller housing
split 2×4
large socket under the impeller
after the 2×4 have been knocked down and the impeller is in the housing
knicking the impeller gently in the rest of the way using the large socket and a piece of wood underneath
finished product