Gear oil leak on Mercury 3.5 HP Fourstroke

I have a practically new Mercury 3.5 HP four stroke leaking gear oil around the base of the prop. This is a slow leak but very concerning. It’s out of warranty and I am a DIYer. I also notice water getting in so I assume it entering same way the oil leaks. I have changed water pump myself with no issues and changed the gear oil with no issues. Question: is there a rubber washer that slides down the shifter rod at the point it goes into foot? Also, is there a prop shaft seal that could be the culprit? If so is it easy to change out on this small motor? Thanks for your help.

Normally the prop shaft seal. Did fishing line get on it? Very simple to change, about 15 bucks. Sweet little motors. The shift rod seal is normally okay. Salt water affects can irritate any point of entry, of course.

I don’t think so! I did remove The prop to see if anything looked out of place and saw nothing. I’m thinking this may be a bad seal due to the motor sitting idle a long while. I have not found any videos of this repair on this particular motor. I know there are two bolts that I must remove to get inside the prop shaft housing. Just don’t know if the seal is easy to replace without having to use any type of puller or special removal tool. Thanks for your help.
micheal

Micheal, remove two screws, pull out the casting around the shaft and leave shaft in its original position with gears inside the housing. In order to get a hold on the casting, turn it so the "ears" are free to grab (use a channelock or something similar and a rag to prevent scratching the paint). Set the casting, which holds the bearing and seal, on a hard surface on top of a socket or something similar that has an opening big enough to allow the seal to drop into as you tap it out from the propeller side. Use an old flat screwdriver or something similar. Note: the direction the old seal came out, with regards to the "lip". Install new seal with a socket.....or something similar, just the right size. If the replacement seal is made of a synthetic compound inside and out, use a little lube of some kind so it goes into the housing without damage. If the outer part of your replacement seal is metal, then use some permatex, silicone, or something similar, to give a lube as well as help with sealing the metal to metal fit. The big o-ring that goes around the casting/bearing-seal retainer, can usually be re-used, however, they are quite inexpensive and you could just get a new one. Make sure there are no burrs on the gear housing and lube up with something like gearcase oil when you press the casting into place. Use a little grease or anti-seize on the threads of the retaining screws. Refill with grease and you should be golden.

I found this diagram. In your professional experience is this the diagram one for my motor? Also which part number on this diagram is the culprit. I can find the part when I google the part but the names on this part diagram are confusing me a little.

Could not get the diagram to paste so I sent you the link to your private message.

I would pressure test to find the part that is leaking.-----On the propshaft bearing carrier you remove bearing first before removing the seal.----Install new seal and then push the bearing back in.

That right, Racer. If he has the 2 screw mounted bearing retainer, this model has a shoulder so the seal comes out towards the gear set. He has indicated that he has the spanner ring retained unit, however. So we need a model number, Micheal.

Model number 1F03201HK

Sending pic to message.

Alright guys I think she is fixed. Thank you Tim for your detailed instructions. It worked like a champ. Took me all of 15 min to repair. Hope you guys have a Merry Christmas!!!
Micheal

Great job, Micheal. Always happy to help if we can here. I have very little boat repair here in Northern MN through the winter months, so I like to follow the forum. I also learn from my peers here as well. Remember, the best teachers are also the best students. Same back at 'ya.