Late 80's 7.5HP Mercury

JayT_B · Apr 15, 2012

Well on her maiden (for me) voyage today, she shut down 100 hundred yards from the ramp. I purchased a 14' Lowe with the 7.5 Mercury (Serial# A196682). Well I found out in a hurry that if no water is coming out the 'pee' hole this means water pump or impeller issue. First boat and first motor, I am learning in a hurry. Or at least attempting to. So I figured out how to pull the lower unit. From my understanding the impeller is located down there. After pulling it I do not see a 'star' looking item which is supposed to be the impeller I was told. I have attached two pictures of the unit after pulling. Along with that, is there supposed to oil filling the internal's of the lower unit? If so, there was none. What you see in the picture is exactly how it was when I pulled it. Remember this is all new to me. I also noticed there was no air filter installed either. Being that it shut down I did not try to restart it. Once home I pulled the rope and it pulls very easily, not seized up. What have I done and what guidance can I possibly receive?

Thank you,

Jace

carholme · Apr 15, 2012

Re: Late 80's 7.5HP Mercury

Your s/n comes up as:

7,5 7.5 2-cyl 6611886 0A197111 1985 USA

From here:

http://www.marinshopen.se/Motorer/O...a/Mercury2takt2cyl68hp/tabid/480/Default.aspx

It is a model:

1007215 MERCURY 1985 7.5

Parts Listing:

http://www.crowleymarine.com/mercury-outboard/297.cfm

You will see the impeller as item 25 under GEAR HOUSING (DRIVE SHAFT)

The oil for the lower unit is contained in item 1 under GEAR HOUSING (PROPELLER SHAFT). Items 36 and 38 in the same link are the Vent and drain screws for the lower unit oil.

The service manual for your engine is P/N: 90-86136--1

http://www.ebay.ca/itm/ws/eBayISAPI.dll?ViewItem&item=360367852754&clk_rvr_id=332743100224

Gerry

JayT_B · Apr 15, 2012

Re: Late 80's 7.5HP Mercury

Thank you Mr. Gerry. So the oil in the lower unit, is this something that should be replaced from time to time and if so is it filled through the vent? That opening seems extremely small?

Jace

carholme · Apr 15, 2012

Re: Late 80's 7.5HP Mercury

Jace;

Yes, it should be replaced depending on how much you use the engine. The bottles that the oil comes in have a pointed spout which will fit in the screw hole. The Vent (upper) is opened to allow the release of air as the lower unit is being filled from the Drain plug (lower). There is also a pump available for a few dollars that screws into the Drain and you pump the oil in.

I hope that you looked at the imnpeller in the parts list and you can see where it is under the housing which has the two nuts in your figure 1 of 2.

Gerry

JayT_B · Apr 15, 2012

Re: Late 80's 7.5HP Mercury

With your help I located and removed the impeller. All the blades are down to 'nubs'. Looking above the propeller on the underside of the cavitation plate there appears to be a screen where the impeller/waterpump pickup is. I see pieces of rubber sticking through the slots of that pickup screen which I am sure is from the blades of the impeller. The issue I have is that the screen is riveted on one end and does not appear to be removable. Removing those rubber pieces appears may be a difficult issue.

MassillonBuckeye · Apr 15, 2012

Re: Late 80's 7.5HP Mercury

JayT_B said:
With your help I located and removed the impeller. All the blades are down to 'nubs'. Looking above the propeller on the underside of the cavitation plate there appears to be a screen where the impeller/waterpump pickup is. I see pieces of rubber sticking through the slots of that pickup screen which I am sure is from the blades of the impeller. The issue I have is that the screen is riveted on one end and does not appear to be removable. Removing those rubber pieces appears may be a difficult issue.

You are going to want to get all that out of there thats for sure. I've see guys talk about using weedeater line or mechanics wire to fish through those passages and make sure nothing is blocked.. Which in your case, very well may be. Check the impeller housing as well.. If that was dry, it may have gotten hot and warped.

That o-ring at the top looks like your slinger seal which is supposed to sit down atop the pump housing.. When you take it all apart, thats the last piece you put back on. Use a bit of grease on the Splines of the driveshaft, but Not the very top of it. Just clean. Make sure all your tubes line up with the seals when you put it back on..

JayT_B · Apr 16, 2012

Re: Late 80's 7.5HP Mercury

MassillonBuckeye,

I got the new impeller ordered today along with the o-ring just below the upper splines of the drive shaft. Oddly enough in this parts breakdown I do not see the o-ring or the groove for it just below the splines at the top of the drive shaft. I have added two pictures below and you can see the groove where is sits.

Another question. I noticed there is no air filter installed. When I called the boat store today they told me there is no air filter on this motor. Does this sound correct?

Mr. Gerry, thank you for all of your help. If you have any ideas regarding the above I would most appreciate it.

Thank you both.

Jace

Jace

emckelvy · Apr 16, 2012

Re: Late 80's 7.5HP Mercury

Check out part no. 35 in the diagram, 25-62074. I believe that's what you're looking for.

And no, your outboard does not have an air cleaner or even an airbox. Not much dust out on the water! Some motors have an airbox but that's typically for silencing. From what I understand some newer motors may have air filters, but your motor is a Stone Age design that harkens to the 60's or earlier.

Not that that's a bad thing!!!

HTH & G'luck with your repairs..........ed

JayT_B · Apr 16, 2012

Re: Late 80's 7.5HP Mercury

Ed.....Thank you. I had arrived at the same conclusion. I think the picture is just deceptive. I was hoping to see it sit atop the drive shaft #13, just below the splines, to ease my confusion.

carholme · Apr 17, 2012

Re: Late 80's 7.5HP Mercury

Jace;

The above is correct, Did yours have the slinger, item 33, installed at the base of the driveshaft, sitting on top of the waterpump? It is a thick rubber ring and you should make sure it is there when you re-assemble.

Gerry

MassillonBuckeye · Apr 17, 2012

Re: Late 80's 7.5HP Mercury

Nothing goes up near the splines as far as I know. I assumed that slinger seal had just risen up the shaft somehow. It should sit all the way down on top of the pump housing. Maybe its too lose. Worn out. It supposed to fit very snugly on the driveshaft so it stays in place on top of the water pump housing.

JayT_B · Apr 17, 2012

Re: Late 80's 7.5HP Mercury

Massillo: I am beginning to think you are correct, no o-ring at the top of the shaft. Just a groove for nothing.

Mr. Gerry: Yes, the slinger is there. It appears #35 is supposed to hold the slinger in place. I can only think that the o-ring at the the top of the shaft was just stretched out and risen to the groove just below the splines of the upper drive shaft. When I go to pick up a new impeller and o-ring I at the boat store I will ask to look at their picture and explain what I have found. I am going to drain the oil from the lower unit and see what is there.

I tell you what. You guys have been great. Especially for the new boat owner with no experience at all. You guys may not get the thank you's from others you help out, but it is truly appreciated. It really is. Thank you very much.

Jace

Mi duckdown · Apr 18, 2012

Re: Late 80's 7.5HP Mercury

the o ring is supposed to be there. replace it, and gease the spine before installation.

JayT_B · Apr 28, 2012

Re: Late 80's 7.5HP Mercury

Gentleman,

New o-ring is installed, all of the old rubber pieces of the impeller have been removed, new impeller installed. I just came in from trying to reinstall the lower unit. After trying several times to get the lower unit installed I am having issues. Water pump pickup tube is lined up, once I start pushing the lower unit up, it stops about 1.5" from being fully seated. How can I assure everything is lined up when sliding the lower unit up?

Jace

JayT_B · Apr 29, 2012

Re: Late 80's 7.5HP Mercury

Also, can the gear shift shaft only be installed one way? With the gear shift in neutral, I can pull the rope slowly and the propeller turns. Should it do this? When I run it in a barrel with water I can not tell a difference between neutral and forward. Not sure what I am supposed to be seeing.

Jace

JayT_B · Apr 29, 2012

Re: Late 80's 7.5HP Mercury

all is good. got it handled.

JayT_B · Jul 30, 2012

Re: Late 80's 7.5HP Mercury

The motor has now completed two days of fishing with no problems and runs great. When I got home tonight I was looking at the prop. There is a small amount of oil coming out of the back where it slides into the housing. I noticed it running down and dripping off the gear housing. I am assuming from looking at this picture: http://www.crowleymarine.com/mercury-outboard/parts/297_160.cfm that item numbers 61 & 64 need to be replaced. Am I on the correct track here?

Thank you,

Jace

oldman570 · Jul 30, 2012

Re: Late 80's 7.5HP Mercury

After the motor has set for a while unscrew the LU lower drain plug and see if the oil is milky colored or any water comes out. If it is, the seals leaking and could need to be replaced. New seal washers should be put on the drain and vent screws atleast every other time they are removed as they will leak and let water in also. The oil comming from the prop could just be unburnt oil that was in the fuel also. Checking the LU oil will tell what is happening. Might be just unburnt oil from the fuel, draining from the exhaust housing area of the motor.

Late 80's 7.5HP Mercury

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