Wow! Learning engineering in high school with old outboard motors is not something I got to do. Sounds like fun. Lucky students!
I would reccomend trying the gaskets without extra sealant initially. It’s way easier to add sealant later if a gasket leaks without than to accidentally get sealent cured in places it shouldn’t be and have to clean it out.
To me, all your gaskets look fine except the head gasket. It looks iffy, and a little cracked. If the old head gasket did not split when the cylinder head was removed, I would not try to replace that gasket with the one you have there unless the installed one obviously had an issue. Assuming that upon dissassembly the old head gasket stuck to either the cylinder head or cylinder, I would not remove it from there as it is sealing and trying to remove it may break it.
If the current gasket is no good though, might as well try your replacement one!
Not sure what’s in your lesson plan but please make sure they know these basics (that I put sort of in order of importance here for you) so they can go fix other old outboards in the future without damaging them:
- Minimum 16/1 fuel mix in most outboards of that age, as they have plain bearings not roller bearings so they need more oil than newer engines.
- The water level should be above the impeller before starting the outboard, not just above the water intake holes as not all of the pumps self prime. Because of this, a standard (5 gallon?) hardware store bucket is not a big enough test barrel.
- Most rubber water pump impellers tend to get brittle over time and need replacement or the engine won’t cool properly. Replacing the old impeller is a VERY common thing to do before running an old outboard that’s been sitting.
- Keep the lower unit gears lubricated, and slowly refill with marine grade oil from the lower screw up to the top to avoid creating air bubbles. Some non-shift 1950s outboards take thin grease instead (not the common NLGI #2 – that’s too thick). Most outboards older than the 1950s take thin grease in there gearboxes. EDIT: Actually I should say most outboards older then the 1940s take thin waterproof grease in their gearboxes. I have thought of more exceptions in the 1940s since writing ‘the 1950s’ and I noticed I used the wrong version of ‘their’ for that sentence.
- It is very important for both the motor and its operator’s safety to torque the flywheel nut to specification and keep it that tight. The vibrations might try to loosen it. Don’t let that happen. Also is a good idea to torque cylinder head bolts (in an alternating sides pattern to reduce warping) and connecting rod endcap bolts too.
- Use Ethanol-free gas as old rubber parts were not designed to resist ethanol and can weaken with exposure to it. Surprisingly, ethanol gas can cause corrosion to metal parts too.
- Air cooled powerheads take air cooled oil, as opposed to regular outboard oil for water cooled outboards. The oils are different because of the different opperating tempuratures associated with the different cooling systems. Many air cooled outboards have a water cooled exhaust. They still have an air cooled powerhead (so take air cooled 2-stroke oil), but some have a rubber water pump impeller too so only run them in water. Others use pressure from the propellor to force water into the cooling passages without an impeller, but this last sentence is more of a fun fact than a must know for your students to go and succeed on their own in the future.
I hope this helps you and your class!
