Re: Replacing engine mounts
Here is a summary of the engine mounts replacement on SV Yankee:
On Brian’s (SV Indigo) advice, I measured the actual position of all four engine brackets in horizontal and vertical direction and marked the footprint of each engine mount on the stringers. I wrote the required height of the supporting nut on each new mount after I marked them with port/starboard and front/aft. That saved me tons of time for the alignment after the new mounts were installed.
I also identified the two lifting lugs. The forward lug is a bit to port, located adjacent to the motor oil filling cap, the aft lug is more to starboard near the air intake.
First I disconnected the coupling bolts and took off the four nuts on the engine brackets. Since the shaft seal is a PSS type, the rubber bellow acts like a spring pushing the coupling tight against the engine. I moved the PSS rotor on the shaft about ¾” toward the engine to release the tension. Then I separated the coupling halves and put a ½” wooden board between the faces of the coupling. That way the coupling could slide on the wood when the engine was lifted up.
Next I tackled the forward mounts because they are in easy reach from the cabin. All screws came loose without any problem. For lifting, I attached a shackle (biner) to the forward lug and connected it with a web string to a 2x6. The 2x6 was set across the cockpit and was supported on the cockpit seats. (Biner and websling are part of my mast climbing gear and the 2x6 is used as jerry can board). Then I pushed up the 2x6 with a pry bar alternating between port and starboard side. As elevation was gained, I put shims under the 2x6 to secure level. By lifting the engine up this way, I could take the old mounts out and slide the new mounts in aligning them to the marks. The alignment nuts of the new front mounts were preset to the noted elevation. I re-installed the screws and lowered the engine.
The more difficult part was to hoist the aft of the engine. The lifting lug is offset to starboard. Lifting the engine using the described method, left the port side of the engine sagging. I also had to unscrew the raw water filter, the muffler, and part of the raw water hose so that these parts could tolerate the lifting movement. I rigged another websling to the aft port engine bracket and used a 2x4 to bring it up. I could take out the old mounts and put in the new mounts. The new aft mounts were preset to the noted level. A good marking of the old mounts’ food print saved time with horizontal alignment.
After the engine was lowered down on the new mounts, I took control measurements of the engine brackets to calculate what alignment would be needed. I moved the engine vertically by using the adjustment nuts and horizontally with a 2x4 until I was in the range of the previous measurement. Then I removed the board between the coupling halves and got the coupling back in place. I had to tensioning the PSS at the same time to avoid water coming in. The new mounts were preset pretty good. I could center the coupling halves with hub and bore immediately. There was only a vertical alignment necessary.
Since I work faster with the metric system, the alignment calculation is done in metric. I measured a gap of 0.35 mm at top of the coupling. Zero gap at the bottom. The diameter of the coupling is 100 mm. The distance of the engine mount is 412 mm. The thread pitch on the bolt of the engine mount is 1.5 mm. Applied all this, a full turn of the engine mount alignment nut corrects the coupling gap by 0.36 mm. So I did, using the front mounts of the engine. After the alignment I could not get a 0.1 mm feeler gauge in anywhere.
Next I mounted the washers and nuts on the engine brackets. When torque is applied to these nuts the mounts can twist easily. I hold the fixed nut at the top of the u-shaped mount with a 24 mm wrench to offset the twisting force. Finally I checked the coupling gap once more and installed the four coupling bolts.
Manpower: 1 person
Tools: Short 24 mm wrench, 24 mm bit, 14 mm bit, extension, ratchet, feeler gauge, screw drivers, Allen wrenches for PSS and split collar, wrenches for coupling bolts, 15” pry bar.
Auxiliaries: 2x6 spruce, 2x4 spruce, wood shims ½”, 1”, 2”x4”, 2”x6”, 4’ web slings, shackle, split collar for 1” shaft to work PSS rotor.
Purchase: 2 engine mounts #100, 2 engine mounts #150. Genuine Yanmar. Total cost: $550.
SV YANKEE PSC34 #274