Does anyone know what rpms I should be getting with a 27 hp kohler Go Devil Longtail out of the water? I'm getting around 3,700 seems a little low. Just got this motor earlier this week so kind of new to this.

If it was a surface drive you would want to adjust...

But 3700 is likely to be fine with longtail - as a "safe" starting point....

Have you run it solo yet ???

If you can actually get close to the rev limit solo with cav plate submergered - you
might want to tweak it... I usually ran more like 3500 with normal loads unless I pulled it up
and ran "surfacing mode" to gain an extra mph or 2 or cross a sand bar.... Then I might turn 3800 to 3900 to get absolute max speeds....

No I haven't ran it solo yet. I took it out yesterday with me and a hunting buddy and it ran around 3500 ish I think. I'll take it out today with a GPS and see what it will do. Giga what kind of grease did you use to grease the shaft with? The instruction manual mentions Aqua-Lube but I'm not sure if I can get that locally. Can you recommend something that I could find at an auto parts place or Lowes/Walmart? Thanks for all the help. It's nice to have a site where you have some guy's that know what they are talking about. I have a hunting buddy that ran his girlfriends dads MB 35 HD last season and of course now he knows everything there is to know about all mud motors. And if its not a mudbuddy it not worth a damn. He was trying to tell me I should be getting 4100 RPMs out of the water. I knew that sounded really high for a longtail.

Call Go Devil - they ship UPS - I use their grease...

Two tubes will last you almost forever....

When you use them up it will be time for a new set of bushings
and another two tubes... Bout a thousand hours from now...

Or generically use a marine grade trailer wheel bearing grease....

If you want to stay with the red marine grease, go to a Tractor Supply. I know the one here has the Lucas Marine grease and it is red just a =s the one from Go-Devil.

I have the 27 and would run at 3500 with a buddy and light load and about 3400 or less with 3 people, dekes, and huntin chit. I turned it up to about 4150 out of water and now I can push that load at 3500. I just dont give it all the throttle if I don't need it. I normally keep the rpms at 3500 not matter what.

Took mine out today by myself and I'm getting 3800 out of the water and 3200-3300 in the water. Any ideas as to what I should to to get the rpm's up?

Balance...

In your Screen avitar from another boat - I see your gas tank and likely your battery were both in the back of the boat with you....

Same hull my 23 LT did 18mph - till I moved the fuel and battery
up to the extreme front - under the extended deck - then ran 20 mph...

Prop is the other big item - mine liked the 9x6 GoDevil the best....

Get your performance maxed - and the rpms will take care of themselves...

Also - maintenance items - air filter, fuel filter, new hose 1/4 or 5/16 not 3/8th, good bulb - yada yada...

And I catch heck for it - but I am a fanatic about my fuel - I only buy
93 octane Chevron from one or two trusted places - if the boat sits for a weekend then the fuel left over goes thru a water filter funnel into the truck and I buy new fuel.... I never put any additives in my fuel.... If by chance the boat sits for over a month - I remove and purge the fuel lines...

This system makes a noticable difference (to me) in the reliability and performance of my rigs...

Like this weekend - going outa town - got enough fuel for both days
that I just bought a few hours ago - drained the tanks and put the old
fuel into the truck - bought new fuel from my trusted station....

Hey giga not to steal a thread but why do you say 1/4 or 5/16 line and not 3/8.....just wondering?

The dealer may not have set the rpms whenever they hooked up the handle and throttle. I know when the dealer got mine this had to be done. Just adjust your throttle stop screw and set your rpms where you want them. The max high idle speed should be 3750 but I have turned mine to 4150 as they drop when under a load. I think most would agree long as they stay under 4200. Just use common sense and not run it as fast if you know the prop will be comning out the water a lot to prevent over revving.

Just tuned up my 4 yr old 27 kohler MB LT last weekend. My tach was reading 4050 rpms. I agree with alot of the other posts, you should be somewhere around 4000-4200 rpms, but do not exceed the rev limit setting. I agree with gigafowl's approach to the fuel issue. I think the motor performs much better with higher octane fuel as well. Change the plugs often and switch to synthetic oil.

Don't switch to synthetic until you have at least 50 hours on the motor.

Switched to a new gas tank filled with premium gas and was still getting the same rpms for about 1 hour then all of the sudden after I slowed down then hammered the throttle it started running between 3450 and 3550. After I slowed down and started again it wouldn't get above 3300 again, until I slowed down and hammered it again... It seems like it could be something with the throttle cable? I should mention I was running with 2 people with fishing gear today. We slaughtered the hybrid stripe bass with out even having a trolling motor on the boat. I did get some funny looks though.

Ok just wondering because i knew the nipple on the pump was 3/8...I think I just may try some smaller fuel line....I really wish I could find a deal on a bps twin exhaust though.