See full version: How to Remove a Stuck Flywheel on an Outboard
While holding the flywheel steady with a flywheel holder, loosen and remove the flywheel nut with an adjustable wrench. In this situation, the flywheel holder is like a pry bar with a pivoting arm that is used to lock into the teeth of the ring gear. Whatever flywheel holder is used, it has to be particularly strong, as the flywheel nuts on these models are tightened to between 120 foot-pounds and 125 foot-pounds. here
Some maintenance tasks, like removing the powerhead from your motor, may require you to remove the flywheel as a first step. If the flywheel doesn't respond to your polite attempts to remove it, you have a problem known as a "stuck flywheel." Removing a stuck flywheel calls for certain tools, most of which are readily available and most of which are equivalent to the proprietary tools manufacturers recommend. Once you have those tools, its all in how you use them.
Place the crankshaft protector cap over the end of the crankshaft and set the flywheel puller's center screw on the crankshaft protector cap and the arms on the flywheel. Take a strain on the puller with a pipe wrench, turning the puller's center drive counterclockwise until the flywheel is free from the crankshaft. [links]
Remove the flywheel cover. If the cover is secured by rubber grommets, lift the cover at one or both ends to pull the cover off the grommets. If the plastic flywheel cover does not coming off easily, check closely for any fasteners. Use a pry bar to move the automatic tensioner out of contact with the drive belt. Slide the belt off the tensioner pulley and allow the tensioner to return slowly to its spring-loaded position.
Remove the timing pointer if it will interfere with flywheel removal. Use a match-line to ease re-installation. Loosen the bolt, remove the timing pointer and tighten the bolt snugly with a Torx screwdriver. Remove the flywheel nut cover.
Finally, if a lawn mower or tiller blade hits a rock or curb, the flywheel key can sometimes absorb the damage, reducing repair costs significantly. Always check for damage by removing the flywheel to inspect the key and the keyway, the key's slot on the crankshaft. The soft metal key must eliminate play between the flywheel and crankshaft. more
Flywheels on today's small engines serve several other purposes. The fins help cool the engine by distributing air around the engine block. The fins also blow air across the air vane on a pneumatic governor, maintaining the desired engine speed (see Governor System). Magnets mounted on the outside surface of the flywheel are required for ignition. On engines with starter motors, lights or other devices, magnets mounted inside and outside are at the heart of the electrical system. more
The flywheel on your small engine was originally designed to store the momentum from combustion to keep the crankshaft turning in between the engine's power strokes.
CAUTION! Never strike the flywheel. Even a slightly damaged flywheel presents a safety hazard and must be replaced.
The cooling fan was driven by its own v-belt beginning with 1942 models. The engine continued to be cast with the upper bell housing integral with the cylinder block assembly. In the post-war production both Ford and Mercury versions had the larger bore (3-3/16"). more
Water outlets were in the top center of each cylinder head for all 1938 to 48 motors. Water pumps were mounted in the lower front corners of all blocks from this era, and doubled as the front motor mounting pad. more
1946-48 (59A style) pictured above