Bought a 27 yesterday that needs a new prop. Going with backwater h2o prop because I like the one I bought for my 16 I had. The website list two different sizes for a 27..9x6..and..9x7...what are yall running on your 27 and any recommendations?

BackH2O makes good props, I have on of their 9x6 that is 1 mph slower than my present Hill 9x6. Both the last two 9x7's I used on my Kohler 27 MB LT (2004), one a Tiger MB the other a GD 9x7 performed no better than a 9x6 and had more vibration but there are too many variables to enumerate here. It is a trial and error thing, but I would recommend two props anyway- you need a spare at all times. To avoid binding, I take mine off at least three times each year and re-coat the cleaned threads with anti-seize grease. I know Ron Hill props have a lot of critics but I must have got a good one (several years ago on Ebay and real cheap), with a smooth finish and it is barely worn after four seasons. I think all the LT mfg.'s rate the 27 LT for the 9x7 prop but in my case the 9x6 allows me to spin more rpms and decent speeds (19.7 my myself; 17.5 two hunters and gear, GPS), I tweaked the throttle to around 4200 rpms out of the water and run close to 3700 top end in the water. My 1648 grizzly is not ideal but it gets the ducks home for dinner.

Main reason I'm looking for insight is, I'm running a 1642 custom flat. I had a 20 hp with a good prop and was running 19-20 just me and empty. Now I have this 27 hp that runs 18 just me and empty but prop has hardly any cupping. I definitely will be pretty disappointed if I can't get 22-24 empty being it's a 27.......good thing is I only drop 1-2 MPh with another guy.

Yes, you should be realizing at least 20 mph with just you in the boat...need new prop. I am sure you have already tweaked the throttle to around 4200-4300 rpm out of the water. Planing depth of prop, right weight distribution, tune up, fuel system check- if the carb has a "foam pre-breather" around the air filter I would remove it, use synthetic oil and grease (e.g. Mobil 1).
Call BackH2O and get some suggestions from them as to which prop to order.

Still playing and tweaking. I just picked it up Saturday. Once I change bushings, seals, and get a tiny tach I'll do more.

9x7

H finn

Had a 9x6 on my 24 honda. Was a little worn, but pushed light load on 1648 lowe 20mph

Ordered a 9x7 backwater h2o today. Paid Lil extra for shipping and should be here by Saturday. Plus getting a tiny tach tomorrow so ready to see what it's got.

Well I'm disappointed. Got my prop on today. Went run by myself and lab and barely bumped 21. Mostly 20. Adjusted tum tab because it was running too deep. Haven't gotten the tach yet so can't verify rims though. ....... only was I'll be happy about it is if it still rides 19-20 with another person in the boat.

Sorry, poke_chop, this is about the best you can hope for. Beyond 4300 rpm it is counterproductive since we don't have gear reduction to spin a bigger prop. On this site, several owners of 35 LT's have posted speeds in the mid-20's by themselves, so there are limitations. Overall, I enjoy the ride, I've often asked how fast do you really want to be going when you hit a submerged log? The beauty of the LT, one that you'll appreciate, is the reliability and economy when all is said and done. I can sacrifice some speed versus the repairs and costs on most SD's I have come across. We have shallow water/hard bottom areas so the LT with the smaller props shine, my round trip is around 12 miles so I do just fine. A stout push pole for reverse. I just get up a little earlier in the morning.

I ran a 20 hp on this same exact boat and was running 19 with same load. Now I have 7 more hp and get 1 mph. Don't make sense

Yea I figured it will do better in the nasty stuff just figured something was wrong to gain 1 mph with 7 more hp. I don't want a speed demon just thought more hp equals more speed

Yea that's what I hope it to still keep a good top speed with a load and torque.