1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

[tunerauto]

I just bought this boat and the PO started it for me before I bought it.
Started up great with a questionable battery.
He serviced it and weathered it before storing last winter although the spark plugs and gear oil hadnt been changed in 3 years but he said they had minimal run time.

I just pulled the screw to drain the gear oil and water came out 1st before the gear oil followed.
Water was very clear, about 1/4 cup of water.
Is this normal? I would think not.
I did however wash the boat and outboard 3 days before I started the drain and fill procedure.
Is this water possibly from washing the unit?
Where would it get in at?
I was very careful when washing the unit and didnt use high pressure .

 

[thefairlaneman]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

A little water getting into the lower drive is not unusual. As long as there is plenty of gear oil the water wont hurt it but you need to drain the water out and fill the case with oil EVERY time you run it. Mine ran ok for years like this and the problem was the shifter shaft seal. You may want to consider a complete lower end seal kit.You arent going to get water in the lower gear case from washing it. IT is for sure coming in because of a bad seal.

 

[tunerauto]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

Thank you. At $1.99 a tube for oil and since I will eventually be stepping up to a larger motor I will just drain and fill after each outing . Thanx again.

 

[cell]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

Seems like its cheaper to just get new drain plugs,and seals....


http://www.iboats.com/Mercury_Outbo...4976909--**********.167331175--view_id.271511

If that doesn't cure it then it might be the pump gasket,ect.Looks like cheap insurance....I wouldn't like to be out on the water with a lower end that doesn't go.Water isn't supposed to be in there.If you found water in your car's transmission would you just leave it in there?

O yah nice toys you got...But you forgot to list your boat.

 

[Aqualift]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

My 65 Merc 500 has a similar leak. Since buying it a month ago, I have routinely drained and replaced the gear lube after each lake trip with the cheap 85W-90 Supertech stuff that comes in a 1Qt bottle. Mine is the shift shaft seal. The marine repair place has one on backorder, so I might eventually have it replaced as it needs a special bushing removal tool.

 

[tunerauto]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

Well got new nylon washers and just refilled it .
Man that was messy! lol
Topped it off from the top(fill) hole after I was done since I lost a TON of gear oil trying to get the bottom drain plug back on.
Replaced the Spark plugs with some new NGK's aswell.

The boat has ran like this for 3 years and the water in the bottom end has been in there for that time aswell. Its ran great and Im not gonna replace any parts til after I get it out in the water for a day and then drain it to see if we have water in it. Ill go from there.

 

[cell]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

The little bit that leaks out is good.The manual says to let a bit out,so theres room for expansion.If its totally full then it could blow....well not blow,but it can leak out the seals on a hot day trailering it to your favorite lake.



I see you have your boat listed.....hmmm...maybe its bout time I listed mine.

 

[thefairlaneman]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

Seems like its cheaper to just get new drain plugs,and seals....


http://www.iboats.com/Mercury_Outbo...4976909--**********.167331175--view_id.271511

If that doesn't cure it then it might be the pump gasket,ect.Looks like cheap insurance....I wouldn't like to be out on the water with a lower end that doesn't go.Water isn't supposed to be in there.If you found water in your car's transmission would you just leave it in there?

O yah nice toys you got...But you forgot to list your boat.

The foot on an outboard and a cars tranny is comparing apples to oranges. The marine oil used is not the same as the oil used in a cars tranny.

 

[cell]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

My point was why would you leave water in any gear case?.....I know the difference's of a merc lower end and a auto transmission....which with an automatic tranny it is possible for coolant to get into it through the transmission cooler cooler if integral with the engine radiator.

A gear case... is a gear case no matter how you slice it.You put anything in it other than the proper gear fluid, i.e water,and your looking for failure.

 

[tunerauto]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

Well I didnt loose "alittle" when I was filling it . I lost alot as it took me along time to get the screw in and seated properly. I allowed oil to drain from the vent hole after I topped it off from there thus leaving room for expansion. My mechanic ability leaves me to believe this should work fine.

 

[thefairlaneman]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

The point is that a little bit of water which will settle to the bottom doesnt affect the oil which is on top around the gears. A complete teardown and replacement of all the seals in the foot would cost hundreds in labor alone and if the engine is used only for week end boating I see no problem. Now if the boat were to be used in the open ocean I do agree that ANY problem even minor should be corrected.I ran my merc for 5 years (summer use) with the same problem and it didnt hurt a thing.I drained out the ounce or two of water after each use and put 50 cents worth of oil back in each time. I hope the foot was drained and filled with oil before it sat for years because then the water may have caused some rust which wouldnt be good. Now an old johnson or ruddy with the electric shift in the foot wouldnt do for any water seeping into the foot.

 

[tunerauto]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

I agree.

The gear oil hasnt been replaced in 3 years but has had maybe 8 outings on it for fishing maneuvers.
Gear oil wasnt very dirty at all and water was crystal clear.
I was mostly concerned with interior deterioration , rust , on the internals but the PO has had zero problems with this motor for the last 3 years .
Im inclined to think it will be ok.

 

[cell]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

The point is that a little bit of water which will settle to the bottom doesnt affect the oil which is on top around the gears.

thefairlaneman,

Ever hear of milk shake.Also the water isn't at the bottom while the outboard is tilted at the house.In fact it doesn't just sit there at all.It churns with the oil and creates a milk shake.Thus lowering the viscosity of the oil,and rendering it useless for the application.... To tell a boat owner That its o.k. to have water in the lower is irresponsible,and that my humble opinion.

tunerauto,

I had water in my lower before too.I don't know how long it was in there,because I found it when I bought my boat.I checked out the lower end,and fixed it.Still works today.Would it still be working if I didn't fix it?Who knows....but my family boats with me,and I won't put them in that position.

When in doubt.......call Mercury up,and see what they have to say on the subject.

 

[thefairlaneman]

Re: 1975 Mercury 500 thunderbolt 50hp 4cyl - drained gear oil , water came out 1st!

I thought my answer based on my own experience applied to his question. (name added to ignore list for offensive comment)