raising Yamaha 50 one, two, or three mount holes

40 mm thick timber is between the alloy transom and the Yamaha mount bracket which rests on a 65 mm wide x 300 mm long alloy surface centered in the transom's top, when the top two mount bolts are through the top two mount holes.
If I raise the Yamaha with the top two bolts in the 2nd, 3rd, or 4th set of mount holes, the gap between the mount bracket and the 65 x 300 alloy surface obviously stresses the bolts.
Would a simple timber wedge hold the ~91 kg load and remove the stress from the bolts?
(for example, with the top two bolts through the 4th set of mount holes, the air gap looks like 60 mm at the front and 55 mm at the back, of the 65 mm wide alloy transom surface.
Thanks for your advice.

Ayuh,.... It sounds like yer tryin' to mount a long shaft motor on a short shaft transom,.....

I suggest ya get a jack-plate, before yer motor rips itself off the transom,...

bondo said:

Ayuh,.... It sounds like yer tryin' to mount a long shaft motor on a short shaft transom,.....

I suggest ya get a jack-plate, before yer motor rips itself off the transom,...

Click to expand...

Thanks, bondo, and you're probably right.
I just measured from the bottom of the 'V' to the top of the 65 mm wide alloy mounting surface at 580mm(=22.83 inches). The tiny 'keel' is 20 mm(less than an inch) below the 'V'.
When I bought the boat, the Yamaha 50's mount bracket was supported by the 65 mm wide(fore to aft) alloy surface, and the Yamaha's 'anti ventilation plate' in the trimmed position looked slightly below the bottom of the 'V'.
The motor is hanging from a beam right now, and the leg is tilted up away from the bracket.
I was just going to leave the Yamaha where it was, until I bought some alloy 'wedges', to try to trilm the motor further down, but the wedges moved the steering tube directly into line with the transom edge, and my first idea was to raise the motor just to get the steering tube above the transom!
Today, I'm fastening 18 mm thick plywood over the 40 mm thick timber slab, hoping to move the steering's moving parts 3/4 inch behind the transom.
If the 3/4 inch gap allows the steering pieces to slide OK, I'll hope to put the motor back at its previous depth.
I'll photograph the result soon.

I typed the transom height wrong: it should have been 480 mm(=18.9 inches) to the bottom of the 'V', and 500 mm(=19.7 inches) to the bottom of the keel.

I can't quite picture that, but understand what you are trying to do. For best performance and maneuver, the anti-ventilation plate on the engine should be dead even with the bottom-most point on the transom. For every 12 inches of offset from the from the transom, the anti-ventilation plate should be one inch ABOVE that bottom-most point.

chawk_man said:

I can't quite picture that, but understand what you are trying to do. For best performance and maneuver, the anti-ventilation plate on the engine should be dead even with the bottom-most point on the transom. For every 12 inches of offset from the from the transom, the anti-ventilation plate should be one inch ABOVE that bottom-most point.

Click to expand...

The motor probably was bolted 60 mm too low, but I also wanted the 5 degrees more depth of tilt from the angled wedges.
Without the wedges behind the 40 mm wood slab, the steering mechanism was an inch in front of the transom.
With the wedges behind the 40 mm wood slab, the steering mechanism was impeded by the transom, so raising the motor was hoped, to clear the steering.
After gluing plywood over the 40 mm wood slab, the steering will be behind the transom, so raising the motor is just an option.
My question is, what packing is needed between the motor's mount bracket and the horizontal support surface of the transom?
The support surface also has tilted 5 degrees, higher at the front, because of the wedges, so that, even if the previous motor height is used, there will be a gap of about 1/4 inch between the motor mount and the transom's horizontal support surface.
Thanks.

Jack plate would help