What to look for when diagnosing lower unit? 73' Johnson.
I just picked up a '73 Johnson Seahorse, 20hp (model# 20r73)
I removed the fill and vent plug for the lower unit oil and a small amount of brown crap water came out. About a tbsp worth. I don't know a lot about motors, but I do know this isn't good. I also noticed the prop would just spin on the shaft whether in forward or reverse. So, I removed the lower unit to see wtf was going on. The prop issue turns out to just be a sheared pin. The person before me must have hit something to cause that.
Everything in the lower gear unit looks good (considering). Everything spins well and I don't see any missing teeth on any of the gears, or signs of damage. No shaves or pieces of metal. Everything looks lined up also.
But...There was obviously something to cause the gear oil to be gone and some water in there. If I'm not mistaken; the entire lower unit should be filled with gear-oil right?
Where do I need to be looking for a place where water can get in and oil to get out? Is there a way to diagnose this type of issue?
The o-ring in the shift rod bushing in upper half of the lower unit will leak.
the seal in the prop shaft bushing leaks too and you most likely will find a worn groove in the prop shaft when you pull off the bushing.
Nope. #24 shift rod and specifically the bushing and internal o-ring that supports it. And #25 prop shaft bushing and seal.
#36 is a thrust washer.
#27 o ring usually has so much sealer around it never leaks.
Reply With Quote