Hi, I just found this forum surfing for some info on my son's 3 HP Johnson Sea Horse. It is a JW-10 which is the 1952-54 model. It starts and runs fine, but the gas cap is cracked and leaks badly when the motor is tipped up. I told him I'd search for a replacement. I'm not doing very well.
I did a quick look at both of those links. They are definitely going to help.
Steve, you have the same engine. Greg likes all the comments he gets about his. However, he changes the lower unit oil about every five tanks of gas (water gets in). Is that normal? I told him the seals or whatever must not be very good anymore. The link to parts should help with that. Thanks again.
Is he changing the gaskets on the drain and vent screw every time? That is the number 1 spot for water intrusion. If not I would replace them, then run it again to determine if the leak is fixed. If there is still water intrusion, he will need to pressure test to determine exactly where the leak is, or simply replace all the seals. Steve will definately be 1 of the guys to talk to on here about the older motors. Good luck.
Just for future....
To pressure/vacuum test a lower unit:
a) drain the gear oil
b) use an appropriate adapter with a gauge tee'd in to apply pressure or vacuum. No more than 15 psig for pressure. You can use a bicycle pump or any other compressed air source for pressure. For vacuum, you need a vacuum pump.
c) LU should retain some pressure or vacuum for 45 minutes minimum.
d) If pressure doesn't hold, submerge LU in water to find leak source [possibilities: drive shaft seal, prop shaft seal(s) (usually two), shift shaft seal and the fill/drain screw washers.]
e) replace offending seal(s) as required.
I have the engine but actually have not got it in the water yet... it's on a long list of things to do... But for any engine there should not be that kind of water infiltration so do as HT says...
But in the meantime, changing it regularly is a good thing to prolong the life... also consider using synthetic LU oil (I know it costs more) as it's supposed to work much better than regular oil when it's been compromised with water...
GREAT old motors..have 3. Bulletproof.
I have a good lower (weedless..angle drive) that I switched out on one, for a later straight drive.
And a day late on a cap..just sold my last one. Keep an eye on Ebay...
Interested, PM me, or email me .. email@example.com put 3hp in the sub line.....
Can't remember what kind of seals are in the LU of those little Johnsons from the early 50's. If it is losing regular marine LU lube/oil regularly, consider using Lubriplate 105 white engine assembly grease instead of the more fluid LU oils. Those older LU seals really weren't engineered for modern LU lube/oil. The Lubriplate will not emulsify with the water and thin and run/leak out. You can find Lubriplate at just about any auto parts store.