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Posts: 1828
| The question is really whether or not the transom is designed for [what's called] the point moment created by the motor/transom connection. If you have doubts, a transom saver posted to the trailer is the solution.
And the longer version... If you're interested, here's how it works:
Your motor has some weight, W, which is its mass multiplied by gravitational acceleration. It's usually a few hundred pounds, say 500 LB. The motor's weight "acts" downward at some "moment arm", or horizontal distance away from the plane of the transom, shown as 'r' (in my sketch). Multiply W x r and you get a "moment (M)" that has to be "resolved" in the transom. So the transom supplies a "reaction force (FRy)" upward and a "reaction moment (MR)" to support the motor. This is all shown in red. The moment is what can kill the transom.
If you add a transom saver (shown in green), this resolves the moment (M) by being loaded in compression and providing a [mostly] horizontal reaction force. I forgot to put it in the sketch, but this force acts at some [mostly vertical] distance away from the motor/transom connection. That distance multiplied by the force in the transom saver post gives you the reaction moment that otherwise would be required from the transom. It saves the transom.
When your boat is bouncing along the highway, the system would be dynamically loaded, meaning the magnitudes of the forces and moments vary from many times greater than the static state, to actual negative values (when the motor is "bouncing up"). So when the motor is actually "bouncing" up, the transom saver wouldn't be under load anymore. It could in fact become loaded in tension, or the motor could pull away from the lower-unit-bracket of the post, so the transom saver could slip out. If this happens, it tells you that there was a whole lot of "bouncing" going on, so it's a good thing the transom saver was in there.
I think it's best to compress the transom saver a bit with your hydraulic tilt and use a bungee or something strapped around the back of the lower unit to keep the post transom saver in place when the boat/motor are bouncing up and down.
Attachments
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 transom saver.jpg (180KB - 685 downloads)
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