Advice - Leaking Oil Reservoir 1995 Mercury

[russ]

I have a 1995 Mercury 75 that is leaking oil from the reservoir with the engine tilted up for travel/storage. I replaced the top cover/filler opening last fall and it's still leaking. Does anyone know of any reliable fixes for this issue? Not only is it messy and costly over time but I'm really not too happy about the potential of oil entering the water. I've started using oil absorbent pads, but that is at best a stop-gap solution.

TIA

[-JR-]

can you see a crack or is it coming from the drain plug.

[mikebossy]

at the end of the boating day, as you are loading your boat, pull the gas line off while it is still running, with the engine still in enough water to **** out the hole, let it run until the engine runs out of fuel and dies, this will drain the carbs of fuel and oil and thus it wont leak, then turn off the engine at the console, you're done, now you can hook up the gas line for next time, and tilt the motor and it will not leak, works for me on my 94' 125 and on my previous 89' 115 Merc, also dont fill your oil tank more than half full at any time, just a precaution against the spillage

[Ddawg]

Most likely the plastic tank opening has gone out of round and the cap won’t seal.
Snowmobile have the same problem, they make a metal insert that fits into the oil tank opening and keeps it form, stopping the leak. I would measure the tank opening and have one made. Here’s a picture of one.

https://uploads.tapatalk-cdn.com/20190702/0a20966a3493141b69977956126f1511.jpg


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[Puma]

Can you pre mix your oil in the gas tank and be done with the oil injection system ?

[Sooner]

Most likely the plastic tank opening has gone out of round and the cap won’t seal.
Snowmobile have the same problem, they make a metal insert that fits into the oil tank opening and keeps it form, stopping the leak. I would measure the tank opening and have one made. Here’s a picture of one.

https://uploads.tapatalk-cdn.com/20190702/0a20966a3493141b69977956126f1511.jpg


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I was just going to say the same.

[russ]

Can you pre mix your oil in the gas tank and be done with the oil injection system ?

Built-in fuel tank, so I would prefer not to especially since I need to deal with jerry cans and my screwed up shoulder. The engine itself starts and runs pretty well. The oil leaking out of the square oil filler is the problem. Sure wish the reservoir was mounted remotely on the boat itself since it's the tilting that allows the oil to leak.

[mikebossy]

interesting what ddawg had to say, in regards to that perhaps you should fill your oil tank about 3/4 full at home on trailer, take off the engine cover,then have someone tilt the motor all the way up slowly while you try to figure out where the oil leaks from and go from there, if you have any mechanical ability at all its probably not a hard fix, getting the oil tank out isnt rocket science nor is putting it back in, only thing that sucks can be taking off the bottom cover of engine, best if you have little hands, the piece to be made is a very interesting idea, i'm gonna look at mine this afternoon and see where it leaks, if it still does when the carbs arent full of gas and oil

[mikebossy]

as for what Puma said, if the oil injection works dont bypass it for mixing in the tank, thats a definite no no, waste of good, working technology

[Jamie Black R/T]

I had a 1995 75hp merc too and it did the same thing....theres a foam gasket under the cap that gets saturated with oil and will drip

I replaced mine and 2 trips later it was leaking again.

I just stopped filling it up so much....keep some oil on board.

I sold that boat but if i had kept it i would have put a transom saver on the trailer to support the motor....that way you dont have to tilt it all the way up to use the motor lock.

[russ]

I sold that boat but if i had kept it i would have put a transom saver on the trailer to support the motor....that way you dont have to tilt it all the way up to use the motor lock.

I've been wanting to get a transom saver for it as it is. The bigger problem is if the boat is in contact with water overnight. The motor will have to be tilted up fully so it's not in contact with the water which could potentially allow aquatic life to infest the lower leg of the engine. Honestly, it was something I had never considered until one of the lake neighbours left his boat tied to the dock for a week with the motor down. Then he had to clean out all the freshwater shrimp that took up residence and had plug up the water cooling galleries. Heaven forbid if something worse were to take up residence like zebra mussels.

[LutherDLG]

at the end of the boating day, as you are loading your boat, pull the gas line off while it is still running, with the engine still in enough water to **** out the hole, let it run until the engine runs out of fuel and dies, this will drain the carbs of fuel and oil and thus it wont leak, then turn off the engine at the console, you're done, now you can hook up the gas line for next time, and tilt the motor and it will not leak, works for me on my 94' 125 and on my previous 89' 115 Merc, also dont fill your oil tank more than half full at any time, just a precaution against the spillage

If you're confident that the problem is the oil reservoir leaking then so be it, but I would definitely make sure it's not just the carbs as this post called out. I have an '89 Mariner 75 and the previous owner stopped using the oil injection system and started premixing because the "oil tank leaks". It wasn't the oil tank, it was just the carbs leaking once they were tilted up. They still leak a little bit if I let it run out of gas, but I've started doing what's described above and it's made a huge difference.

[barbless]

Built-in fuel tank, so I would prefer not to especially since I need to deal with jerry cans and my screwed up shoulder. The engine itself starts and runs pretty well. The oil leaking out of the square oil filler is the problem. Sure wish the reservoir was mounted remotely on the boat itself since it's the tilting that allows the oil to leak.

That could be the problem when you mentioned it was a square filler. I just assume it's attached to the engine under the cowling. Guess Merc new it would leak being square so want you to by a new reservoir or cap (not cheap). Did you try pulling cap off and cleaning really good. Can't help with yours but I have a Yamaha 150 2 stroke and had the same problem leaking out the top when tilted. Mine was an easy fix it being a round cap. Put a zip tie around the rubber part of the cap sealed and done. No more mess or leak. I feel for ya wish I could be more help. Mine has a one litre res on the engine and gets fed by a separate 9 litre reservoir. Can you give a pic of the filler? Funny both my tanks have round caps

[mikebossy]

if someone can 'teach' me how to post pics i can post some of my 125, it has the rectangular filler cap as well, so i can show you what i do, though pretty simple, as i said i would, i looked at it yesterday, engine cover off, started with reservoir half full, tilted engine fully up, checked to make sure oil didnt hit top of filler cap, lowered engine, added oil, and so on, until the oil level when tilted came to just under where it would run into the cap and foam gasket of the cap, then i tilted motor down til level and drew a sharpie line and marked it as Max Fill Line so i knew how high to fill it in the future, guess im lucky even though its a 94 if i fill it high enough to engage the cap and gasket it still doesnt leak, however if i dont run out/drain the carbs at end of day it will leak out of the carbs, if i drain the carbs no leakage, voila really think this is your answer if you would just give it a go

[russ]

I think I'll try your method mikebossy, it's gotta be better than an oily stern and polluting the lake.