Changing Motor Mounts – Part 1

Last year, we bought new motor mounts from Poly Flex. I wrote about that here. It was a project for this winter. Time to get to it. I mustered the courage and conned my friend Bruce into helping me out. I figured he was good for all the hard stuff. Sooner or later he is going to get wise to me. I have to get as much work out of him as I can before he does.

There are three hatches in our salon. When all are removed along with the supporting crossbars, we have reasonable access to the engine room. At least we can stand up much of the time. And I didn’t hit my head on anything. Bruce did. More than once. Removing these gave us as much working room as possible.

We need to change eight mounts. Each engine weighs around 1100 pounds.

The first step for us was to disconnect the propeller shafts. In our case, four bolts on each side did the trick.

The big challenge for us was to lift each engine enough to remove the old mount and replace it with the new one. A lift of three inches was all that was needed to complete the swap.  There isn’t anything under the engine to push up on, so I decided to lift from above. With the hatches removed there was nothing but air above the engines. We may have done it the easy way, or we may not have.

I decided to use a lever to lift the engines. We would lift the front, swap the mounts, then lift the back and repeat. A steel cable connected to the engine would allow the lever to lift the engine to the required height. We cut 4×4’s into a crossbar to span the opening in the floor, and two short pieces to support the crossbar at the ends. Then we cut a long piece to use as a lever and notched the end hold the steel cable.

When we first started, the wood slipped around a bit. The solution was to cut dado’s in the 4×4’s where each boards met. That took about ten minutes to complete and fixed that problem.

Here are the old front motor mounts. You can see the rubber has been squeezed out and the mounts are well worn. As it turns out, these are actually the wrong mounts for this engine. More on that later.

The same is true for the rear motor mounts. There is little clearance between the mount and the arm coming of the engine.

Here is the new front Poly Flex mount. Very fancy compared to the ratty old mounts.

We started on the front port mounts. Those were the easiest to get to. Then we moved to the front starboard mounts. It took us about three hours to get everything set up and the four front mounts (2 on each engine) changed. Not bad for having no idea how to do it.

We were feeling pretty good about the progress, but that’s where the fun ended. The back mounts didn’t fit. They are too wide and interfere with the mounting arm attached to the motor. Nothing we can do except get different mounts. Remember in this post where I said Hugh from Poly Flex came out to the boat twice to make sure we got the right mounts?

I contacted Thermoboat about the mounts and after exchanging a few emails, I discovered they don’t actually have a model to fit our engines. Too bad. They seem like great mounts. Remember where I said Hugh came out to the boat to be sure we got the right mounts?

I decided to go with what I know will work. I probably should have just done that from the start, but I apparently don’t learn well from past mistakes. I contacted Brian Smith at American Diesel. They are the Lehman experts.

I sent Brian a few photos and we talked on the phone a few times to be sure we had the right mounts. Brian then sent me photos and measurements of the mounts he had available and we agreed on which ones we should use. That’s where I learned the current mounts are for the Lehman 135 instead of the Lehman 120.

That’s where we end part one of our exciting story. The Polyflex mounts are headed back to Thermoboat and new mounts from American Diesel are on the way to us.

More to come …

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