It seems my replies didn't get posted. I hope this isn't going to show up a third time.
Probably because the first 2 posts of a new member is scrutinized by the moderators to see if it is a legitime post or someone trying to use this forum for advertisment or whatever... This goes quickly or takes a little time, depending on an actual human actually doing that job. :welcome:
200 lumens max is great. Last year I used a nightrider trailrat which I believe put out 190 lumens.
if 200 lumens for 7 hours is impossible, I could get away with either 1 battery swap, or getting a light that would run @ 50 lumens or so for 65-75% of the race.
I'm glad ~50-200 lumens range seems to be OK for your race, because that is really easy to arrange without breaking the bank.
As an example, fenix LD20 will run for at least 9 hours (factory claims 13 hours) at 50 lumens. (Using 2*AA batteries and costing $50-60). Maximum is 180 lumens for about one hour and half (factory claims 2 hours). Buy two, mount one on the bow and run it on 50 lumens, it will last the night. Leave that light alone... Have the other ready for turbo mode (head thightened) and turn it on whenever you need more omph.
And of course you need to consider backups... which leads to the classic CPF advice: Simply buy more flashlights. Instead of fumbling with batteries you just change flashlights. Come Desember, you can give them away as christmas presents.
Oh, and did I mention that if you use AA batteries, use eneloop nimh batteries?
Now that is cleared - do you think you need maximum throw with the smallest possible hotspot or a wider, but not as far reaching blob of light? I've never paddled at night, but I think the latter would be most useful, allowing you to see a larger cross section of the river at a glance.
(You're not really searching, which is when throwers really shine - you are assessing as quick as possible which part of the river you want to be in). The LD20 gives you this wide blob of light that reach ~100, maybe 150 meters downstream. You may of course augment this setup with something with more throw.
You may also consider something based on more potent battery technology, giving a increased performance and/or runtime. (li-ion 18650 is probably your best choice then) The downside is that this technology is alien to many, and requires that you do a bit of homework on charging cycle, safety procedures and the potential risks. Li-ion batteries has about half the energy density per mass as TNT explosives, so a little bit of education is recommended. :thinking: AA batteries seems more friendly to the unenlightened, so to speak... and more than good enough for the job. (Did I mention you should use rechargeable eneloop AAs???)