We still like this name for a boy but do you think it’s too feminine?
Nope. Seems totally male to me, probably because my only point of reference is [name]River[/name] [name]Phoenix[/name].
Hmm… I think its one of those names that changes its feel depending on middle names or sibling names. But for me [name]River[/name] is all boy. I met this adorable little boy on the train a while back, who was commenting on the “ding-ers” (or the train crossing lights, haha.) His name was [name]Miles[/name] and his little brother who was asleep on mum’s lap was [name]River[/name]. I say keep it on your list, to me its screams boy - in a good way 
But like most things to each their own.
Best Wishes! 
My other kids are [name]Holden[/name], [name]Sawyer[/name] and [name]Izabella[/name]. Our middle name considerations are [name]River[/name] [name]Elias[/name], [name]River[/name] [name]Elijah[/name] and [name]River[/name] [name]Jonas[/name]
I think [name]River[/name] [name]Elias[/name] sounds very masculine.
That’s great then, your names are semi-traditional which makes [name]River[/name] stand out as completely masculine versus him being the siblings of [name]Laken[/name] and [name]Quinn[/name], if you know what I mean I love both [name]River[/name] [name]Elias[/name] and [name]River[/name] [name]Jonas[/name] by the way!
It always seemed male to me, but after friends considered it for their daughter, it just totally seemed to fit a girl!
It sounds masculine to me!
I’m a really bad person to ask on this because tomorrow I would name three sons [name]Phoenix[/name], [name]Devon[/name] and [name]Sydney[/name]. At leats one of these would be unacceptable to a lot of people but I love them all so much for boys. [name]River[/name] *seems" female to me, but that’s only because I hear a lot of people talk about it on girls, I prefer it on a boy though, by a long shot.
Since I grew up at a time when [name]River[/name] [name]Phoenix[/name] was a major teen heart throb, it is completely masculine to me. And I would bet that at least 90% of the [name]Rivers[/name] you will meet would be boys. But I could imagine a girl named [name]River[/name] too. Of your choices, I prefer [name]River[/name] [name]Elias[/name] the best
[name]River[/name] is all boy to me!
I prefer it vastly on a boy (as the only [name]River[/name] I know personally is male and he’s the handsome, quiet artist type) but I do think it works fine on either. [name]River[/name] [name]Phoenix[/name] brings it into the masculine, [name]River[/name] [name]Tam[/name] (from Firefly/ [name]Serenity[/name]) allows it to go to the girls (though she was kick-@ss).
Keep it on your boys list. It’s goes fine with your other kids, [name]River[/name] [name]Elias[/name] is very handsome.