Things You'll Need
Block of wood
Your lawn mower engine takes a lot of wear and tear each mowing season. The engine not only has a large bearing load put on the engine from the mower blade, but it also must perform in hot weather. Over time, the components in the engine wear out and you have to decide whether to get a new mower or replace the engine. Installing a mower engine takes some work, but it is less costly than buying a new mower.
Replacing a Riding Mower Engine
Search for the gas tank next to the engine. Follow the fuel hose attached to the base of the gas tank to side of the carburetor on the engine. Squeeze the clamp holding the fuel hose to the side of the carburetor and slide the clamp up the hose a few inches.
Pull the hose off and direct it into the bucket to capture the gas.
Unscrew the red cable from the side of the starter with the proper-sized wrench.
Follow the throttle lever to the throttle linkage on the side of the engine. Unscrew and remove the throttle wire from the side of the engine with the correct screwdriver head.
Unscrew the bolts holding the engine to the frame of the riding lawn mower. Position a wrench on the bolt head on top and on the nut under the mower frame. Remove all the bolts.
Lean the engine forward and pull the belt off the pulley attached to the crankshaft under the engine. Pull the engine off the mower frame.
Place the pipe wrench on the crankshaft area above the pulley under the old engine. Hold the pipe wrench with one hand so the crankshaft doesn't rotate and then put the proper-sized wrench on the bolt holding the pulley on and unscrew it with your other hand. Place the pulley on the crankshaft of the new engine. Screw it on tightly.
Place the new engine on the riding mower frame. Slide the belt around the pulley as you set the engine down on the frame. Tighten all the bolts and nuts through the base of the new engine to secure it to the riding mower frame.
Reattach the throttle linkage, starter cable and the gas line to the new engine.
Add oil to the full line on the oil dipstick and fill the gas tank with gasoline to properly lubricate the engine.
Replace Push Lawn Mower Engine
Tip the mower on its side. Lay the block of wood between the deck edge and the blade to act as a wedge.
Fit the correct-sized wrench onto the bolt holding the blade to the base of the push mower engine crankshaft. Unscrew the blade.
Lay the mower down flat again. Follow the throttle lever to the throttle linkage on the side of the engine. Unscrew and remove the throttle wire from the side of the engine with the correct screwdriver head.
Unscrew the bolts holding the engine to the mower frame. Position a wrench on the bolt head on top and on the nut under the mower deck. Remove all the bolts.
Pull the old engine off of the push mower deck. Place the new engine down.
Tighten all the bolts and nuts through the base of the new engine to secure it to the push mower frame. Reattach the throttle linkage.
Lean the mower on its side. Screw the blade onto the base of the crankshaft. Use the block of wood as a wedge when you are tightening the bolt. Lay the mower flat again.
Add oil to the full line on the oil dipstick and fill the gas tank to properly lubricate the engine.