I know the 27hp kohler is 725cc and my 25hp kohler is 725cc! correct me if im wrong!

where does the 2 more ponys come from? is it a different carb? if so would a 27 carb fit on a 25??

not sure what 2 more hp would matter but that thought just ran across my mind!

You can put the carb/intake from a 30 on it. And the heads. The carb on the 30 is a 2 barrel. The one from the 27 will, fit, but may already be the same one not sure. You can also do a lil work to yours to get more power. Is it a down draft or side draft?

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Talking about the carb not the crankshaft. I've been told adding the carb/heads will yield more than 30hp for the 25's and 27's. Don't really know why, maybe different cam or stroke or something. Maybe because you would normally port and polish the new heads. You could deck your stock heads to do the same thing. Depending on which carb you have, you may be able to get more out of your stocker than the 2 barrel. New intake/carb is about 300-350. Reworking the stocker can possibly be done for free if done yourself, or pretty inexpensive to have it done.

how do i determine if its a side draft or down draft? (im new to mud motors and small engines)

what is decking the heads? will head work shorten the life of the motor?

The heads for the 30 raise the compression, but they were designed to run on your block. If you decked the heads to the same tolerance, it would pretty much be the same thing. Wouldn't hurt your engine. Decking the heads is basically taking metal off to make the combustion chamber a lil smaller, thus raising compression and creating more power. I went with the 30 heads just because the price difference was negligible (maybe even a lil cheaper), and you get to keep your stock heads should you ever choose to go back.

To tell which carb you have, see how the air inlet is oriented. If it draws air in from the side of the engine it is a side draft. If it draws air in from the top, its a downdraft.

how much do the 30 heads cost?

im guessing its a downdraft because the carb is on the top!

Cool, the downdraft has more options. The heads were 230 where I got them from. I got some other stuff with mine so it was a lil more, but if you move all the stuff over from your old heads thats about all you'd have to buy. Give skip at www.mid-atlanticperformance.com a call. Good dude and these motors are his specialty.