I have these wheels. I was impressed by the marketing (made in Germany etc) but couldn't find many reviews. I've had them for a year and I have to say they are pretty good. They don't get in the way of turning the outboard.
The only criticism, is that the wheels are fairly small. This isn't a specific criticism of these wheels, a lot of the launching wheels have similar sized wheels. They work well on a proper slipway or compacted estuary shingle or sand, but on soft sand or loose pebbles they will dig in. I know it sounds a bit like British rail "the wrong kind of snow" but the surface you are going to pull them across is definitely the biggest factor.
Strength wise, these seem very strong. my outboard is 51kg and when I have tried to pull them on soft sand and they have dug-in, they have taken a lot of force without bending. I've now learnt though to assess the surface and only try and launch on firm ground.
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