Scott C,
You have a 123 which was the first and only Hydro model made in the 1X2/3 series. It was introduced midway through the 3 years that IH produced this series. I can see that it has a Kohler engine which should be a model K301A and puts out 12 hp. The Walboro carb currently on your engine is a replacement as it would have originally came with a Kohler/Carter carb. A #26 size carb is correct for a K301.
Walboro carbs use plastic floats instead of the donut brass floats used in Kohler/Carter carbs. After 30-40 years of use, the original Kohler/Carter carbs wear at the throttle shafts and get loose which allows air into the carb and they won't run good at idle. There are washer repair kits and bushing rebuild kits available to remedy this problem but not everyone knows that so they just put a new replacment carb on which is unfortunate because the Walboro carbs are not as good as the original Kohler/Carter carbs and they don't have a high speed adjustment screw. If you have a small engine shop near you it would be best to take the carb off and take it with you to get the correct carb kit. Warning, Walboro carb kits can be pricey so prepare yourself.
You have a 123 which was the first and only Hydro model made in the 1X2/3 series. It was introduced midway through the 3 years that IH produced this series. I can see that it has a Kohler engine which should be a model K301A and puts out 12 hp. The Walboro carb currently on your engine is a replacement as it would have originally came with a Kohler/Carter carb. A #26 size carb is correct for a K301.
Walboro carbs use plastic floats instead of the donut brass floats used in Kohler/Carter carbs. After 30-40 years of use, the original Kohler/Carter carbs wear at the throttle shafts and get loose which allows air into the carb and they won't run good at idle. There are washer repair kits and bushing rebuild kits available to remedy this problem but not everyone knows that so they just put a new replacment carb on which is unfortunate because the Walboro carbs are not as good as the original Kohler/Carter carbs and they don't have a high speed adjustment screw. If you have a small engine shop near you it would be best to take the carb off and take it with you to get the correct carb kit. Warning, Walboro carb kits can be pricey so prepare yourself.