Murray Missile 

I'm getting a 2021 Marlin 5 in partial trade for an old truck, guy bought it new during the whole COVID hysteria then only rode it a couple times (like a few hundred thousand other people). He showed me the receipt so I know it's legit and not stolen. I don't "need" it, I have several bikes that aren't getting ridden now BUT, it's my size and I LOVE the metallic orange paint. However, I'm not loving the Tourney components so much, I know they're reliable but I think that paint job deserve better. I know, great logic LOL. I have a complete new Deore XT 3X10 setup I bought for a build that has hit a wall because of tire clearance limitations and I was all set to swap out the Tourney for the Deore XT but I got to thinking about a 1X instead. I'm almost 67 YO and mainly ride VERY hilly chip & oil or gravel roads and a mixed surface tow path with sand, clay, pea gravel, etc. with only a few small inclines on an old '88 GT Karakoram with a drop bar conversion, brifters and 3 X 8's. I do it at a fairly leisurely pace, I get there when I get there but I do like to take the path less traveled occasionally. Does a 1X have an advantage over a 3X for the type of riding I do? I don't mind spending the money, the bike parts littering my garage shelves are testiment to that, but if the only gain is a little less weight and the "simplicity" of no FD then I'll probably just go with what I have. Been riding 3X's for decades so a little shifting with my left hand is no big deal but I'm always up for trying something different IF it will gain me something. The Tourney drivetrain will go on the other project to make it whole and then it will get sold.

2old

My wife just acquired a bike with 1X12 (10 - 51 rear AIR) and, along with (and definitely enhanced by) 29" wheels/frame turned into a new, better, more confident rider. Accordingly, I got one too and really like the 1X system. It's nice where we ride and the hills go from easy to hard to almost too hard and we don't need to worry about anything but the rear cassette. Probably others will have differing opinions, but we love the 1X. BTW, if the Marlin is relatively new, the frame is identical to higher end Marlins AFAIK, and excellent. Three of my friends just purchased 2022 Marlin 7's for their first MTB's and really like them.

Darth Lefty 

You will have to replace a lot on that bike to get to 1x. It has a riveted chainring crankset and a freewheel hub.

Murray Missile 

I saw that on a couple YT reviews, decent frame with box store bike components. When he said it was a Marlin I was hoping it would be the 7, then I'd just take it as is........... no, that's a lie LOL. I modify EVERYTHING. I'm also swapping to a slightly better Suntour fork and Vuelta SLX wheelset while I'm at it.

Darth Lefty 

Well... since you have a good start of parts maybe you can make a go of it. The XT crankset should be a 104 bcd, yes? Then all you need for the front end is a chain ring. Maybe some chain ring bolts. The XT 10 speed shifter will work with any of the new RD's. You are going to need a 10 speed wide range cassette and an RD big enough to hit the bottom gear. Lots of options for that stuff. If you have a chain it might be long enough.

1x enables a lot of cool things. The front shifter delete is nice! Not going to argue that. Some of the benefits are not relevant to the Marlin 5 in particular. In a fancier current bike it also widens the suspension pivot shafts, simplifies the suspension optimization for pedal bob, makes room for plus tires. The left shifter lever position is freed up for the dropper. For tradeoff first in particular the cassette is huuuge and inexpensive ones are heavy, and it's still not the bonkers range of a 3x.

Murray Missile 

If I go 1X11 I'd replace the entire drivetrain but the more I research the more I'm inclined to stick with the original Deore XT 3X10 plan. I already have everything, just needed a frame with some tire clearance. I'm used to riding a 3X, tuning them is no issue for me plus I don't think my OCD would allow me to not have a LH shifter to balance out the cockpit LOL.

rosefarts

Fwiw, I had 10sp XT on a 3x10 bike a few years ago.

I think it was 20-30-40 up front and 11-36 rear. It was buttery smooth. No hesitation and no missed shifts.

I like the simplicity of 1x, but to get decent climbing I had to go to 30 x 11-46, with an 11sp. I felt the gaps were too big with 10sp.

I enjoyed the project and have since replaced the bike but in retrospect, I probably should have stayed with 3x10.

You’re doing more of a bare frame build up so it’s not exactly the same, so leaving it as is isn’t as much of an option.

zen_

Trek bikes hold their value pretty well, and the casual models like the Marlin are super easy to sell, so I would just cash out $400-500 rather than upgrading a bike that has QR axles, a straight head tube, and a coil fork. For the same $ you would spending upgrading that thing you could just buy a Polygon Xtrada 7 that has a great Deore 1x12 drivetrain, thru axles, tapered head tube, a boost rear, and a low end air fork (non-boost unfortunately).

Not to totally trash the Marlin though, it is fine for what it is. If you're going to upgrade something, leave the 2x8 and replace the fork with a Suntour Epixon air fork for $200.

Murray Missile 

I've decided to go with the 3X10, even when I was young I wasn't a strong climber so I'll take all the help I can get.