84 90 hp Mariner,gear oil coming out from small hole on Lu

tuffy84

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Jan 9, 2014
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Hello everyone,thanks for having me.I 'll have a 84 90hp inline 6 mariner.the boat sitting in garage since November,The garage is heated to 45/50 degree Last couple days very cold,I left the garage door open for an hour tops,The next day I noticed oil coming out on the small weep hole by top of MY next to the top screw.Any help or suggestions .Thank you and Happy New Year to everyone.
 

racerone

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Dec 28, 2013
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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

Was the gear oil changed recently ?-----Any water in the lower unit ?---------Most lower units have drain holes for water to prevent freeze damage.-----This could be oil from winterizing or normal oil from the exhaust.-----------Gearcase can be pressure tested if you are worried.------------30 year old motor and has the gearcase ever been resealed ?
 

tuffy84

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

I keep the boat inside,I did not change the oil in last two season,my impeller start going out late October so I was going to change that in the spring.I got this boat 5 years ago,before that it was sitting outside for seven years
 

racerone

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

There may be water present in the gearcase.----Water shrinks in volume till it reaches 39 degrees F ( 4 degrees C )------Then it starts to expand agian.----So a lower unit cooling down can put extra pressure on the seals and cause leakage.-------I would pressure test the gearcase to be sure.----That motor needs a new impeller every 2 years.
 

tuffy84

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

Thank you for your reply,the oil is not milky,it is kind of dark but smell like gear oil. I went to bass pro one guy said drop the lower unit but do not drain the oil .He said I should change the seal behind the water pump,But my think is the weep hole is higher than the top screw on the lower unit,You when u fill the oil the top screw is the overflow,and engine is all the way down in last month.Thanks
 

racerone

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

Just take your time on this project, not that hard to do.-----Lower units are pressure tested to find the leaks and yes the rubber seals do wear out.
 

carholme

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Sep 4, 2010
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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

Drop the LU first and note if you see any oil around the shift shaft bushing and seal, items 41/42 in this link:

Mercury, Mercruiser, Force, etc. - GEAR HOUSING (DRIVE SHAFT) - 90/115 H.P. (INLINE)

This will tell you if the shift shaft seal is leaking.

If oil is noticed mainly around the driveshaft it will probably be seals 18 and 19 in the same link. If either the shift shaft seal or the waterpump base seals are leaking, it would be worth replacing them before doing a pressure test, saving you the effort of pulling the bearing carrier, item 63 in this link:

Mercury, Mercruiser, Force, etc. - GEAR HOUSING (PROPELLER SHAFT) - 90/115 H.P. (INLINE)

As you haven't included your engine s/n and you are sure it is a 1984, here is the parts list for your engine:

90/115 H.P. (INLINE) - Mercury, Mercruiser, Force, etc. Parts Lookup

Gerry
 

tuffy84

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

The s/n is 6399037.Why is the oil just start coming out now, after 60 days?Thanks Lazlo.
 

carholme

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

That s/n come up as:

MARINER - ( 90 H.P. (1980 ))
Serial No: 06399037 Model No: 7090620

As this is a 1980 rather than a 1984, here is the correct parts list for model 7090620:

MARINER 90 - Mercury, Mercruiser, Force, etc. Parts Lookup

If the oil you are seeing is coming from the small 1/8" drain holes, these are there to allow water to drain from the cavities when the engine is vertical after the last removal from the water. They must be kept clean as if water does freeze in there, it can rupture the case. Don't know where you live but if there was any trapped water in there and was mixed with oil from the leak, starting to freeze when you left the doors open may have pushed it out through the drain.

Gerry
 

tuffy84

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

I live in Portage,in,2 miles from lake Michigan.We had -17 with windchill-35 that day..I left the door open for 45 min.So should I drain the gear oil before I drop the lu or it is to late? Thanks again.Can you tell me where did you look up the year? I checked a couple of sites and still coming up late 83.maxrules.com
 
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carholme

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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

The information for your s/n, 06399037 is from the Mercury site:

Parts Catalog | Mercury Marine

There is no need to drain the gear oil but as it is the down time of the year, it will not hurt anything, at least dropping the LU will tell you if there is visible oil on the top of the unit.

Gerry
 

MH Hawker

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Jul 13, 2011
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Re: 84 90 hp Mariner,gear oil coming out from small hole on Lu

More than likely its un burnt 2 stroke oil it is very common for it to drain out over time.
 
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