An onager-hueristic estimate:
It's over 9356 nautical miles from Honolulu to Mombasa, but that's the great circle route, which goes over the Russian-Chinese border, where a boat can't go. But being so close to the equater, the actual sea route might not be too much longer. So I'll use 10,000 nautical miles.
A freighter in such a trade would be doing well to make 15-20 knots, maybe as low as 10 knots. Thus it would take 500 hours at 20 knots, 666 hours at 15 knots, and 1000 hours at 10 knots. That's about 20.8 days, 27.8 days and 41.7 days respectively. So a month or so, maybe as much as 6-7 weeks.
BTW, an onager is an Asian wild ass, a heuristic estimate is a guess, so that make this a Wild Ass Guess, or WAG. :)
I've been waiting to use that for quite some time, although I have used it at least once before. I first read the term in an official report from a contractor to the USAF, and I had to go home to look it up, no desktop computer or Internet in those days, around 1974 or so.
How long would it take to go from Hawaii to Seattle by whatever would have been available if WND is right about newborns not being able to fly.
BTW, an onager is an Asian wild ass, a heuristic estimate is a guess, so that make this a Wild Ass Guess, or WAG.