Khephren said:
When do you draw the line and say 'now it's an islamic state'? My instinct would be to go with when the ruler converts.
I disagree and I'll explain why after this transcription.
A History of Malaysia and Singapore by N.J. Ryan (1976) p. 23 & 24.
Iskandar Shah's reign was a relatively short one and when he died in 1424 he was succeeded by Sri Maharaja Mohammed Shah. It was this ruler who according to the Sejarah Melayu (the Malay Annals) was converted to Islam after marrying the daughter of the ruler or Pasai. During this reign the influence of the Muslim-South Indian Tamil group of merchants continued to grow, helped naturally by the ruler's own conversion to Islam. But at the same time conflict developed between this Muslim trading community and the essentially Hindu-Malay ruling class.
...
When he died in 1444 Sri Maharaja left two sons. The younger, Sri Parameswara Dewa Shah, was a Hindu and was supported by most of the Malay chiefs, for he was born of a royal mother. Though he was the younger son, he succeeded his father to the trhone. This was because the mother of his elder half-brother was a Muslim-Tamil commoner and was not accepted by the Malay chiefs. This elder brother, following his mother's family, appears to have become a Muslim and had taken the name of Raja Kassim. He was supported by the Muslim-Tamil faction led by Tun Ali, his uncle, and it was this group which eventually place him on the throne.
After only seventeen months as ruler, the young king, Sri Parameswara Dewa Shah, was overthrown and killed in a coup d'etat led by Tun Ali. Raja Kassim was made ruler by the victorious Muslim faction, and during his reign Islam replaced Hinduism as the accepted religion of Malacca. He took the name of Sultan Mudzaffar Shah and ruled from 1445 to 1458/9. During these years Malacca became the centre of Muslim influence in South-East Asia, and this in itself helped his kingdom to grow in importance. The Muslim-Tamil merchants who had previously used northern Sumatra as the base for their trade now moved to Malacca...
In the first place Islam became the state religion. The general population soon accepted the religion of the ruler for the latter was not only the political and religious head of the state, but the most influential group at his court were also Muslims. Again Islam was not forced on the population; traditional customs were not abolished; as a result, what opposition there was soon died out, especially when Islam was accepted by the leading Malay families.
Now first off, your source is a bit confused as Megat Iskandar Shah followed his father in 1414 and died in 1424 where he was followed by Sri Maharaja Mohammed (check our monarch file to see that we've always had it that way as well). I have another text that talks about why there is often confusion in those early reigns but I forget the argument (see :The fall of Srivijaya in Malay History - O.W. Wolters for more info).
Onto the main argument:
1) It seems odd to me that each individual king would have had to convert to Islam if the official religion had been Islam. Instead, each king appears to have been raised Hindu and only converted upon taking the throne.
2)However, if we look to Sri Parameswara Dewa Shah, he never converted to Islam but rather stayed a Hindu. If we were to accept the idea that we should have a religion change everytime a ruler converts, we'd still end up with a Hindu Malacca for 1.5 year span.
3) As highlighted in this chapter all of the ruling class/nobility were Hindus. It was only with the rise of Sultan Mudzaffar Shah that Hinduism was replaced in their ranks by Islam. If the ruling classes in each province were Hindus, then Hinduism as the religion for each province is sensible as surely they shouldn't be viewed as Sunni to represent the initially small merchant class.
4) As YodaMaster pointed out, in EU2 there are negative effects for having non-state religion provinces. Clearly, the provinces must be Hindu and we would only harm Malacca by having it as Sunni at game start. A two province Malacca, with no overseas territory, is weak enough to begin with, so we don't need to weaken it further by making the province religions counter to the state religion.
5) Finally, this source explicitly states that Islam became the official religion only in 1445 with the rise of Sultan Mudzaffar Shah. Unlike other sources, it also provides the reasoning for why Islam finally became the official religion in 1445. If that isn't proof that this change should be made, I don't know what is.
Combining game play arguments with the information provided by this source, I can only stand by my claim that Malacca should start off as Hindu and then switch to Islam in 1445 via the event I created. The one change I might make is to give Malacca a free conversion in its capital, so that it only has to worry about spreading Islam to Johor, by itself. That might better capture the quickness to which the new nobles were to support Islam.