Engine oil leak at the lower unit

PISTONESAL

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Feb 11, 2008
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Help please!! I have a 2000 Mariner/Mercury 75HP outboard that I got May 2016 and has been awesome with no issues. Now, I saw an oil leak on my driveway. I had a look at the source of the oil leak and it appeared to come from a small 1/8" port on the underside of the fin towards the transom. I can't make it out where it is coming down from inside engine.. What is this little hole for? It is to the above/right of the oil level screw in the lower unit. Anybody have any suggestions please? I tried to upload a picture but it would not work don't know why.

I read this online

"The air diverter box that is attached to the front of the carbs has a small bleeder hose that is attached to the bottom of the engine block. This acts as a drain for fuel that has been dumped out of the front of the carbs when you tilted the engine. That fuel runs down the inside of the exhaust cavity and can come out the weep hole that you see on the lower unit. That is how the fuel/oil mix shows up in that location. P.S. it can also run downt the skeg and look like a lower unit oil leak."

Is this true? Please advise. I would really appreciate it. Thanks
 

racerone

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Perhaps you are not familiar with 2 stroke basics.-----Some fuel and oil mix goes right through the motor and is wasted.----It collects in the exaust housing and drains out wee holes.------This alarms many folks.-------If you are worried then have the gearcase pressure tested at a shop !
 

PISTONESAL

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Thanks for the reply racer one. The oil stopped leaking so I did a test. Yesterday I trimmed the engine up and left it up and today after work I say that it's started leaking again at that weep hole and where the lower unit meets the engine. Does this mean it's engine oil or lower unit oil? Obviously trimming it up caused it to start leaking again.. Anybody else have any thoughts or suggestions? Thanks
 

Chris1956

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Smell the oil. If it stinks like rotten eggs, it is gear oil, and the driveshaft seal under the waterpump is probably leaking. If it smells like gasoline or regular oil, it is 2 cycle oil, and might be normal...
 

PISTONESAL

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I smelled it and I am not sure which one it is. All I know is when I brought it down more started to come out and it was a descent amount not just some residual. Could there be anything else? Also, looks like the previous owner/s was prying with a screwdriver to take off the lower unit where it meets the engine and left some slots on it.. No wonder he put some kind of silicon around it.. Is there a seal on the lower unit where it mates with the engine. Wish i could add a picture here but when I do it tells me pic is corrupt. I have pump kit ready to go but I got boat June last year and they did tell me he just serviced it but who knows how true that is. It spits water awesome out of the tell tale..
 

racerone

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There are many tutorials on ---UTUBE----That explain the 2 stroke motor process.----Fact is some gas and oil go through a 2 stroke engine without doing anything ( wasted ) so to speak.------It runs down the exhaust housing and on to your driveway.-----That alarms many folks.----They think something needs to be fixed !!
 

PISTONESAL

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I get that and it makes sense but are you taking about a river of oil or just a small residual amount:) The last time I went out with the boat, I put the engine up all the way to where I could use the lift support bracket. When I got home to flush the engine, I put it down. I went to get the hose and flusher and when I went to hook it up I saw a good river of oil coming out of that so called weep hole. Is it possible that much oil does not burn? It seems like its a lot. Man, i wish i could post my pictures:(..
 

racerone

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Then you should get the lower unit pressure tested as I have stated before !----And oil is not supposed to " burn " in a 2 stroke.--------That is just an unfortunate thing that happens.
 

PISTONESAL

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So all the oil in the oil tank eventually just works through the engine and eventually just oozes out overtime from the weep hole?
Sorry, this is my second boat and its been a long time since I had my previous one which I did a lot of maintenance on but it was a long time ago. thanks for your help.
 

racerone

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This topic has been discussed many times !!-----Look for this in the frequently asked questions on this and the Johnson / Evinrude forum.-The topic is most confusing to the novice !
 

hardwater fisherman

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Try looking at the the photo upload tutorial, that is listed in the forum rules and guidelines. It may help you to upload your pics. It helped me.
 

PISTONESAL

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No Title

Ok. I took new pictures and they attached now. see below. as you can see, there is a gap where I guess the other owner pryed with a screwdriver I assume. No wonder there is red silicon all the way around. :( I hope when I get ready to drop it this weekend I don't have issues... Is there a gasket where the lower unit meets the engine? I trimmed the engine up a little bit not a lot and really no oil. Just some residual I assume from when I had it all the way up to do this test. I mean, should an engine be trimmed all the way up or not? I have a water pump kit and some other seals and gaskets I got from my sister who works at a marine shop but just not sure what all I need to repalce. Just wanted to get as much info as I can before I do the job:)
 

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Dukedog

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trim it down again after its up for awhile... throw a match on tha drippin's.... if it lights up its fuel/oil.. if not, its gear grease.. a no nose needed test... jus use a little common sense!... no gasket or sealer needed between gear case and down housing...
 

merc850

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According to the posted description this motor is a 4 stroke http://www.iboats.com/MERCURY-75-4-S...iew_id.1701882 and looking at the parts lists there is a dipstick that could be leaking engine oil or it could be leaking LU oil at the shiftshaft bushing; the best way to check this is to match the oil with the engine or LU. I would replace those rusted LU bolts with stainless steel ones (I can't believe the factory used carbon steel!) because you are going to have to replace the impeller more than once.
I don't know if you're operating in saltwater but this chart will keep things from seizing up
Lube-intervalssmall.jpg
 
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Dukedog

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where did ya come up with tha numbers for a 4 stroke... its never mentioned anywhere in tha posts?.. ......... but old and half blind so coulda missed it!....
 

PISTONESAL

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Thanks for the reply. According to the SN of my engine, its a 2 stroke and yes its ran in saltwater. Also the bolts are stainless, just the nuts were not. If no seal is needed between lower unit and housing, then if water gets in between them, it won''t hurt anything? I think it is lower unit oil as I think i see where the issue is but I need to make up a pressure tester to see if I can verify there is no other leaks. The previous owner told me he serviced the lower unit when I got it in May 2016 but not sure if he did the impellar. If I pull the housing to check it, then will I need to replace the gasket if the pump looks good?
 

merc850

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The initial post says: "Help please!! I have a 2000 Mariner/Mercury 75HP outboard that I got May 2016 and has been awesome with no issues" this is what I used to find parts diagram. Just buy the waterpump repair kit from Mercury it will come with gaskets.
 

PISTONESAL

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Thanks for help. The engine is from the year 2000 but I bought the boat ith it last year in May. What if the pump looks good, just replace the gaskets? If no seal is needed between lower unit and housing, then if water gets in between them, it won''t hurt anything?
 

PISTONESAL

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Ok so I replaced shift shaft seals and pressure tested LU and so far all good . Reinstalled which gave me some fits then hook up hose. And good and went fishing yesterday and ran great. I diid notice when returning home and doing a flush there was some water spitting between the LU and where it meets up with engine. Is that ok? Everybody says no seal needed to be put on those edges? Please advise anybody. I appreciate it
 

GA_Boater

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Nothing needed to seal the lower unit to the midsection. Water fills that area up when the motor is in the water.
 
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