When in forward a soon as l give it full throttle it stalls out. Not sure what to do.

Mangled gearbox.
Drop it off and dismantle to find the problem.

This may be a linkage problem, but I'd check the prop first. Are u saying that the engine dies when u give it throttle in forward. Or, that the boat just want go. This engine has a reputation for a very dependable gear case, so I'd be suspicious of hitting something. In which case there would be prop damage. If, there is water in the gear case oil, it is probably gear & bearing failure. l am not sure it is worth repairing if that is the case. Your engine is what 20-25 years old??? l think u could find a used boat for what it would cost to fix yours, if it is the gear case. Good Luck!!!

Disconnect shift cable at the motor, see if u can shift it by hand. if not, sounds like u will have to tear it down for inspection.

Do not know about ur motor in particular but in general, motor dies when u go full throttle, first thing l look at is the spark advance linkage. Might be sticking. If the carb butterflies start opening before the timing advance, it will fall flat on it is face.

Then see if pumping the primer bulb makes it run, if so then rebuild fuel pump.

If it is a 2-cyl, could be a cylinder dropping out (3- or 4-cyl usually just bog down). Either spark failing under load, hi-speed carb jet clogged, or low compression on a cylinder.

First pull the prop. Some real early ones had shear pins, latter called alignment dowels. They would bend & jam up the gearcase. Always us a good prop nut. Next: they had a small bronz yoke about 1/2'' square with a rounded slot in the middle.It is hidden deep inside the lower unit. This slipped over a mushroom headed rod the slid down the middle of the prop shaft & was roll pined to the clutch dog. They used to wear & get so sloppy the clutch would not reach both gears. So u could adjust it to run forward or run reverse, but not both. Next; The shift cable attached to a contrapsion that had an interlock to keep the throttle from moving much when u were in neutral. All this stuff is under the carb. Lots of room easy to get at. The shift adjuster is on a round anchor towards the middle of the motor.It is a ball & socket that threaded in & out on the end of the controll cable. If u can keep u feet out of the prop, u can stand back there with the engine running on water ear muffs & shift & throttle everything till u can figure out the next direction to look. The carb problem is pretty well covered-sounds like the main jet is pluged.. Depending where u live, there r lots of these in barns & laying around-a quick wanted ad should get u a parts motor. Most of the parts interchanged thru the 35, 45, 55 hp models. This is one of the few outboards that used a wedge/hammer approch to taking off the flywheel. The wedge only supported the flywheel while the biggest hammer u have just tapped the crank shaft to vibrate the flywheel off. Use a thread protector.(send the gorillia out for bananas) Set points to .20. Do not believe the timing sticker. It was dropped 5 degrees years ago, so time it to 26 to 28 or less. Remember- u can not hear & outboard detonate. So if ur out running & that giant hand comes out of the sky & slows ur boat down- do not try to drive it home with out finding out why.

adjust the throttle cable