Re: "Might" + present infinitive for past use?
Welcome the the forum, cypriot77.
The first point to make is that the infinitive is not 'present'; it is the main verb that is tensed:
I will try (in the future) to learn it.
I am trying (in the present) to learn it.
I tried (in the past) to learn it.
We can use the so-called 'perfect' infinitive to indicate completion of an activity by/before a known time.
I hope (in the present) to have learnt it by/before the end of this year.
I hoped (in the past) to have learnt it by/before the end of last year.
The system is rather complex with modals, each of which may convey a range of meanings. Sometimes the 'past-tense' form indicates past time (I can play the piano. / I could play the piano when I was nine.), but sometimes it indicates only a lesser degree of possibility (I can see you tomorrow, / I could see you tomorrow.) Each modal construction has therefore to be considered in its context.
Exploration was part of war and rivalry with other nations, so these voyages MIGHT INVOLVE attacks on other ships and towns.
If the crew were thinking 'These voyages may/might involve danger', then we can say:
The crew were worried; the voyages might involve danger.
Here we are using implied reported speech.
If we are thinking now that there was a possibility of danger for the crew, then we can say:
The voyages may/might have involved danger.
A further complicator here is that some native speakers use might as the past/reality-distancing form of may; some see no difference between may and might; some do not use may at all. This makes it very difficult to give explanations of these modals that cover all situations.
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