Yanmar SB12:  Engine Template
This page was last updated on 4 May 2000.

Installing the new engine requires constructing new mounts.  Getting the alignment, position and angle right is difficult and finicky at best, so I decided to build a rough template of the engine to assist me.  The most important features of the engine--the mount locations and the transmission coupling position--are accurately laid out on the template.  In addition, I included rough representations of the cylinder head position and height, the oil pan, and the transmission gear housing, all of which may affect the ultimate position of the engine.

Rectangular template showing four bolting locationsUsing the service manual I purchased for the engine, I consulted the drawings showing the dimensions of the engine and bolting flanges.  I started with a scrap piece of MDF, which I cut to size to represent the four corners of the engine determined by the mounting flanges.  The Yanmar SB-12 fortunately features mounts that are in line with each other fore and aft, which makes for a simple rectangular plywood template.  With the panel cut to the exact size of the outline of the mounts, I then located the hole centers (using the measurements on the supplied drawings) and drilled the holes on my drill press.  


Next, I screwed some extensions to the basic form.  Two extensions were installed, one at each end, to represent the locations of the furthest forward part on the engine (the accessory pulley) and the transmission coupling at the aft end.  The forward (pulley) extension was fairly accurately represented, although this measurement is not critical to the installation.  The coupling extension, however, was extremely carefully measured so that the end is exactly representative of the face of the coupling on the engine.  With these simple extensions screwed to the platform (attached with the scraps of plywood you see here) I added short plywood ends to both extensions, shown belowtemplate3.jpg (42680 bytes) as the vertical piece.  These are used to exactly locate the center of the propeller shaft and, therefore, the coupling.  With the centers marked, again using the measurements on the shop drawing, I drilled small holes through, to allow an alignment string to pass through  both ends of the template.  The string, which will be installed through the shaft log and into the boat, will be used to properly orient the engine and the wooden foundation that will be constructed.

Next, I added some rough representations of some of the other engine components that will in part determine its position in the boat.  Using the drawings, and consulting the engine itself from time to time, I built the very simple, crude shapes you see in the photo to represent the height and rough position of the cylinder head, exhaust manifold (the short horizontal piece near the top of the tall "cylinder head"), the oil pan and transmission housing.  These are important to the installation because they will determine exactly how far aft or forward the engine has to be located to properly clear the hull and cockpit structure.  This is the finished template.  I know it looks funny, but it will be of great help as I continue the installation.  Once I determine the basic position of the engine in the boat, and the minimum heights and positions of the foundation, I may remove some of the extra pieces, leaving only the plywood bolting template and shaft centers. 

Next:  determining the rough position of the engine in the boat, and roughing out the foundation.

Please click here to continue.

Glissando, Pearson  Triton #381

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