US citizen in the US buying a boat in South Africa

[serpa4]

I'm looking at a boat in Cape Town for sale. I live in the US and am a citizen of the US.

I'd need to buy the boat in Cape Town and then leave it there for about 6 months before moving on and then sailing away.
I'm not finding much info on this.
Do I have to leave the country with the boat in a certain time period (30 days?) to avoid paying SA taxes?
I'd register the boat in the US as a US citizen, but not sure how long I can leave a boat in SA till I have to pay some type of fees.
I know in the US if you buy in say Florida, you have like 30 days to leave or pay state taxes. I assume there is something like that in SA, but not turning up much of foreigners buying a boat in SA and NOT registering it in SA.
Any info or links would help, thanks.