Mounting bracket (ACV-P54) bolts don't match Mount

[pschwenn]

With the new Rotax bracket (ACV-P54-Kit-SB see photo below) for Sonex Rotax engine mounts (SNX-P52-02 Xenos #32), the bolts and the predrilled holes on the bracket side are 5/16" OD, but on the engine mount side, they are AN-4 (4/16"), and the receiving holes on the engine mount could not be drilled to 5/16" because they extend outboard with a thin sleeve (see photo) of 4/16" ID and OD about 5/16"->3/8".

There is a small well on the bracket side of the connection to the engine mount for each 5/16 " bolt, and AN-4 bolts could be used there if there was a shoulder washer (such as that supplied between the rubber bumpers, but much smaller) to fit in those wells.

Question: should I somehow arrange to use the more substantial bolts supplied? (There is a sleeve pressed into the holes on the engine mount which could be removed to match the provided 5/16" bolts but the thin outboard sleeve would then have to be cut off - its structural purpose is not evident, and the pressed in sleeve may be there because originally the engine mount was meant to accomodate 5/16" bolts there.)

Question 1: why don't the bolt sizes match?

Question 2: the wells don't have any apparent reason for being (unless to receive my suggestion of shoulder washers) - why are the wells there?

Question 3: the engine bolts, bumper bolts and the supplied 5/16 bolts to make the connection, are all quite massive compared to the AN-4 bolts required by the engine mount. Why would the engine mount be designed to support the relatively massive bracket (meant to properly support and damp the engine) with the much smaller (in mass and shear strength) AN-4's?

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[pschwenn]

Sonex tech support answered me (in brief):

Sleeve (e.g. aluminum} the AN-4 bolt where it passes thru the new style bracket; there is no structural need for a bigger bolt.

The well is just to provide clearance for the bolt head.

[Zack]

I had to make bushing. Here are photos of my bushings on the old style Rotax mount. I don't have photos of the new bushings I made.

http://www.sonexbuilders.net/viewtopic.php?f=60&t=5612