Ok, First I did a search and didn't find quite what I needed. The motor is a 27hp Kohler LT. Out of the water at WOT it is running 3950. In the water with two people and very light to no load it is running 3260 in deep water. The prop is a 9x7 according to the paperwork. I measured the prop and it measures 9 1/8". The motor has 8hrs and no mud time or sand. When I picked up the boat at GD they said that you will increase rpms as the prop wears slightly and should give the best life for the prop and motor etc. I just wanted to know what your feedback is. I have the cavitation plate set and it runs 3-4" underwater. I can sit and drive without it coming out of the water very often. I am not interested in "hot dogging" the motor or anything but it seems like it should be making a little more rpms with such a light load? Thanks again I posted a few pics with this post.

Solid looking rig. I also have a 27 Kohler LT (MB) on a 1648 grizzly. I was getting almost the same rpms as yours with the 9x7 so I tried a 9x6 and increased to 4200 rpm out of the water and top out at 3950 rpms in the water, with less vibration and 2 mph more. I don't have much mud so it works fine. I did tweak the throttle (I assume you did also) to obtain those rpms. If I was running more mud the 9x7 would be indicated.

Hot dog it...

If it is a GD, you should be able to send the prop in to get repitch to 9x6 free of charge. If you will run in mudd and sand, what they said is true. It wear after time, giving you the most prop life. If you won't run much mudd or sand, I would repitch it. If I remenber correctly, optimal RMP's are 3600 to 3700 in water and 3800 means your prop is starting to wear out.
Also I would adjust the govner to get 4100-4200 WOT out of water.

THANKS for the help. I do plan on using in the mud during duck season as needed. I am going to call go devil monday and double check the prop size. I had three of us in the boat the other day and seemed like we were bogging down the motor. just a couple hundred rpms would "dial" it in I think?

I have run a 27 hp kohler on a mudbuddy frame for the past several years and have tried both the 9x7 and 9x6 props. Motor is stock other than a stainless exhaust more for occasional saltwater use than any attempt to increase performance. I can honestly say I prefered the 9x7. Although the 9x6 may let you drive the RPM's up a little more, I found that whenever there was mud, sand, veggies, and stuff in the way the 9x7 did better. I also found that the 9x7 seemed to have more torque in the low end. I hunt usually hunt out of the boat and with blind, decoys, and assorted gear on a 14x48 the 9x7 performed better for me. The 9x6 did give me a a little more top end speed, maybe 1 mph, but that was only when the boat was completely empty, blind was off and just me and the dog messing around. Brand new 9 x 7 was turning RPM's in the 3200's but by the end of the season would be up in the 36-3800's as the prop wore down. You can hit a bed of sand in the dark and take off the cupping on the props pretty quickly. Again, personal opinion, but after trying different props I felt the 9x7 was a better all around performer. Once the 9x6 began to wear down, you may get even higher RPMs but I felt the torque for hunting loads was not there. If you guys run a light boat just racing others to your spots or a fixed blind- then the 9x6 may be your style. I found, at least on my rig, the RPM was more limited by the load I was carrying than the prop I was using.

The governor screw on mine is set for 4050-4100 RPM. My understanding of the governor is that messing with it to change max RPM out of the water does not really affect in the water performance unless you have enough mods to hit the governor RPM when the prop is in the water. It is there to prevent damage to the engine when the prop gets knocked out of the water when running and the engine suddenly rev up. You can bump up the limit on your goverened RPM but unless you are hitting the limit with the prop in the water, it probably won't affect performance much- just my opinion and I am not a specialized small engine mechanic like some guys on here.

Before you go re propping, just make sure the throttle is getting full travel.

Talked with Go-Devil this morning and they want to re pitch the prop to 9x6? Everything is brandnew but I was suprised that 3950 is all they set the engine at new? I pulled the wheel off and going to send it ups in the morning. Great service and I guess this is something that comes up often. He said the motor should turn at least 3400 and ideal 3600 with a light load. Iwill post an update if I have everything back before leaving for work. Like I said great cust service just a bump in the road. No charge to get the prop right. I am more worried about loosing performance with a 9x6, but I am probably worse off now not running at peak hp? thanks again for the help

Got the prop pitched down to 9x6 and ran the boat tonight. rpms came up to 3370 - 3420. Seems to run allot smoother and running about 19.5 - 20 mph deep water? I think i need to readjust the cavitation plate just a hair. thanks for the help.

20 mph. on a longtail is heavenly. Drive proudly.

Here is a quick video I put on youtube. This is a first for me I hope it works!

http://youtu.be/LJItzPwGz1M

Here is another one from the same day running in some grass in a duck pond.

http://youtu.be/upps05W705s

Ain't nothing better than running in the swamp with the longtail! Looks like the prop is running exactly where it should be. My only two observations are 1. Put some hydroturf on the floor areas- you and your trusty companion will approve. 2. The gas tank up front is a good idea for weight and space considerations- is there a way to slide it under the bow? Guess you'd have to cut out a space underneath, kind of a pain, but you'll gain more space. That is a solid hull. I say you are ready to duck hunt in June!