Hello all, I just recently purchased a 27 hp kohler GDLT, my first real rig, I have had outboards but this is the real deal, hah, at least for me at the time. Before teal season I want to tune it up and maybe change some other small things and wanted to see what your opinions were on what to use. Here is a breakdown of what I want to do:

Spark plugs ( Do any brands work better than others, possibly throw a better spark?)
Oil/Oil Filter Change
Air Filter ( K/N?)
Fuel Filter
Exhaust ( Any suggestions)
Prop ( What size, manufacturer)

My goal is not to be a speed demon, but to increase the motor's overall performance without messing around with the guts of the motor itself. The motor is on a 16X44 GD, I hunt primarily in the bay complex and its surrounding backwaters. As of now I haven't clocked it because it wouldn't be an honest way to gauge it beings the prop is 8inch around. I have seen that Robn has a longtail, and was speaking about a three blade prop would this be an option to look into on this motor? Again I know a little but not an expert, any help is appreciated.

You aren't gonna gain too much just adding an exhaust and k&n filter. It won't hurt anything, but its not gonna give you any significant gains.

There are plenty of parts available for the kohlers if you really want to make some power with it. One way to gain a couple reliable horsepower is to put the parts from the 30 kohler on it. Heads and carb/intake. The cam that comes in the 27 is built to have a lil more torque, and works well with the heads and carb from the 30. Or you can add a mikuni, which would be a much better, and smoother running carb than the 30. Also more power...

The regular old champion plugs work fine. You can put the ngk's in there, but no real need for them.

I use a good synthetic oil, but you don't have to.

The k&n is a good choice for air filter and oil filter

Exhaust, EVT or BPS are your options on the kohler. Both should have much better flow, the bps is a lil quiter

Prop, couldn't tell you on a longtail, but someone will help you out

I run the E3 spark plugs on my engine and haven't had any problems. I've read on a few different occasions about some guys having issues with the champions. I bought mine at Sears and I think they were the same price as the champions, so I figured why not.

I use Mobile 1 in my motor.

I have the K&N filter, but I haven't really seen any gains from having it. Probably because I don't have any mods on my motor at this point.

I think on my old beavertail 24hp i was running a 9X4 prop, I can't remember. Since you have a go-devil, i would just give them a call and see what prop they recommend on the 27 longtail and just buy it from them. It will be a two blade. I don't think there is an option for a three blade on a longtail, but i could be wrong.

cb5331 hit on the exhaust issue. I've been waiting for Marsh Mellow to come out with an exhause for the 23, but i don't know when that'll be.

As far as fuel filters, just go to the local hardware shop and pick you up a fuel filter. From what I can tell they're all pretty much the same.

Hopefully this gets you a good start.

i would recommend, as far as a tune up, that you get a carb kit if you dont do with the mikuni carb. its an expensive kit at 60 bucks and dont include much at all, but it sure helped my 25 run alot smoother!!

I have a 27 GDLT and I run a 9x7, which came with it. Its on a 1644 Weldcraft and runs 21 by myself.