Frank Acampora
Supreme Mariner
- Joined
- Jan 19, 2007
- Messages
- 12,004
In a private message, the question of how to rebuild the lower engine mount was asked of me. I have decided to answer here so all can benefit from a refresher of advice I have given in the past.
The lower engine mount on Force and Chrysler three and four cylinder engines will frequently separate. Rather than replacing it, it is quite easy to repair and make better than new.
Take the original mount and remove both halves from the engine. This can be done without supporting the engine because the upper engine mounts will take the weight. You will need to remove the front cover and wedge the engine leg out a bit to get room though.
Once the original engine mount is removed, clean the broken area well as there will most likely be dirt and oil on the rubber biscuit. After cleaning, coat the rubber biscuit and the aluminum mount with a very good rubber adhesive. I use a 3M product designed for commercial use. Be certain the bolt holes are aligned well otherwise you will have trouble reinstalling it. Let dry for a day or two.
Do not perform the next steps until there is NO possibility of the parts shifting, even slightly.
Now, on both sides of the center hole drill one 1/4 inch, or the correct size hole (17/64) to tap 5/16, through the top plate, rubber biscuit, and bottom plate. Take the thick bottom plate and countersink the holes with a 5/8 inch, 82 degree countersink allowing about 1/8 to 3/16 depth. That is: Allow enough depth so that the top of a flat head screw will be about 1/8 to 3/16 below the surface of the plate. This is important because it allows the rubber biscuit to compress. Do not go too deep as it will weaken the plate.
Drill the rest of the thick plate to 5/16 inch diameter to clear a 5/16 bolt.
Now tap the thin plate and rubber biscuit with a 5/16 X 18 tap. Buy two flat head, stainless steel 5/16 bolts at least as long as the engine mount is thick. Screw the bolts in until they are just snug--you do not want to compress the rubber biscuit with them.
Now, grind off the excess thread, if any, and using a center punch, "Stake" the bolt in four places between the aluminum and the threads to prevent backing out.
This engine mount will outlast the engine and will not break again, even if you hit something. If you do break it, you have hit hard enough to damage the lower unit.
Now, let's see if I can find the photos.
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