1989 Force 125 Lower Unit Oil Leak

[MikeAM]

I have a 1989 Force 125 with an oil leak, it is gear oil because it has that distinct aroma that gear lube has. On the leading edge there is a small hole where the oil is leaking from when the motor is tilted. An outboard mechanic said the hole is used for a speedometer pickup, and that an internal seal has gone bad. Has anyone had this problem and/or have information on the seal that can cure the issue? I have not been able to find any trouble shooting information on this subject or an internal passage diagram of the gear housing.

 

[pnwboat]

The 1989 lower units did not come with the hole for a speedometer pick up. The later model lower units that did come with a hole for a speedometer pickup do not have any internal seal in that immediate area that would allow oil to leak out. I would suspect that maybe the top cover on the gear case, or maybe the shift rod seal might be leaking and the gear oil could run into the cavity in the lower unit that sits directly behind the hole. Is it possible for you to post a couple of pictures of your lower unit showing both the complete lower unit and also the hole that you are seeing oil leak from?

 

[Jiggz]

A picture will greatly as requested.

 

[MikeAM]

Thanks for the preliminary info pnwboat, I will attempt posting some pics later today for you and Jiggz to view. As you will see by absence of the skeg, I also have a tilt problem. When I pull the gearbox off to fix the leak issue, I will have a new one welded on. Wasn't much use for 1/2 a prop, so I already took that off.

 

[Jiggz]

I've lost my skeg about 3 years ago and is still missing Lol. Can't seem to find a welder to do a cast aluminum.

 

[Frank Acampora]

The lower units with pitot holes for speedometers had a soft rubber plug that sealed the cavity. There were two different types: A small one held in the cavity by a spring clip and a large one pressed into the cavity. Since the lower unit is not original to your engine there is a distinct possibility that the P.O. simply left the seal out.. If either is missing there will be no harm dome, the impact water will fill the cavity and exit with the exhaust.

Now: if it is definitely gear oil you are smelling then there are several sources. As mentioned the shift rod seal may be bad. Below the water pump is a lower mounting plate This plate contains the drive shaft seal and an O ring to seal the plate to the lower unit casting. Since the shift rod seal can be a bellows, a break here will lose a lot of oil. However, a failed drive shaft seal will also leak a lot of oil so you need to check both. If the bellows has failed you are S.O.L. They are no longer available. Look up a previous thread on this where someone modified the lower plate the accept the hockey puck type seal. If you already have a hockey puck type seal, then you have the option of trying to press it further into the casting and thus tighten it a bit, or replacing it with a new one (about 8 bucks) Drive shaft seal is ar

If you have a lower unit with a bellows shift rod seal (Good idea, crappy design) Remember that if you remove the shift rod that the rod needs to be unthreaded 4 turns from seated to work correctly with the bellows. If threaded in too far, the bellows will be fully compressed and forward gear will either not engage or will jump out of gear under load.

 

[MikeAM]

Frank, thanks for your reply...a wealth of information indeed. Now I am more curious than ever to rip into it, but at the same time a bit apprehensive because of what I might find...it's no fun being S.O.L. It is definitely gear lube, so it has to be a seal gone bad. My dad bought the boat as used (no idea how many owners it had) and then gave it to me. He said it never leaked and was very strict in changing the oil at recommended intervals. After towing it 400 miles is when it began to leak.

Of the manuals I have looked at, I have not found any information about what fits what, tips and tricks, or any accurate descriptions especially internal passage schematics; this forum is fantastic.

For those who have requested pics, I hope they are visible (3ea, leading edge with 1/8" drill bit in speed pick-up hole, right side, and left side). I will post some more pics when I get the wrenches turning...possibly within the next few days.
View attachment Leading Edge.pdf
View attachment Right Side.pdf
View attachment Left Side.pdf

 

[Frank Acampora]

I can see from your photos that the engine is an extra long shaft (25 inch)

. IF you want to repair the skeg you can buy a new skeg (only) from Mercury but it is expensive and the welding will also be expensive. You CAN cut your own skeg from a piece of 1/4 inch thick hard aluminum. Grind the front and back edges to a taper. This skeg will be way stronger than original and if you hit something it will dent rather than bending or breaking. Don't ask me how I know! LOL

I did forget to mention that under the bottom pump plate in the front (encircling the shift rod seal area) there is an O ring in an odd shaped groove. It seals the front oil chamber. It is a marginal seal and when you put the lower unit back together, clean the groove and the lower unit sealing surface well. Install the O ring and coat it with a light layer of silicone seal or permatex. to ensure an adequate seal.

There are no internal passages. The lower unit is a simple big casting open at the top. Gears are stuffed in the torpedo and there are several seals for the prop shaft and the bearing carrier. The top is open . In the front there is an oil chamber. In the rear there is a water intake chamber. In the center is the drive shaft, bearings, and seals When you remove the entire water pump assembly you can see all the openings.

 

[MikeAM]

Thanks a bunch Frank. Anxiety has gotten the best of me, Friday evening is when the socket set will come out. I will post some pics of the inner. I already bought a replacement skeg for 25 bucks, but I don't know the cost to weld it yet. The replacement will need a bit of shaping to fit the nub arc I-85 ground the original skeg down to. Hopefully I will have some pics out here this Saturday. I will check back before the ratchet starts clicking just to see if there are any other tips.

 

[MikeAM]

Hello Frank,

I removed the lower unit this evening, and I think this is the part where you tell me that I am S.O.L. See attached pictures. By the looks of it, someone found the bellows seal around the shift rod broken and tried to repair it with RTV at some point. Do you have any idea what the part number might be? Even though they are not made anymore, maybe someone has one on the back shelf somewhere? According to your description above, I also need to check the o-ring under the seal plate and the drive shaft seal as well.

I do have another question about this gear box: is it single or dual exhaust? When looking for a prop, I ran across that exhaust question. I cannot see a passage where exhaust would flow down through the gearbox and through the prop.

Thank you very much for all your help.

 

[Frank Acampora]

You have a single exhaust lower unit. you can tell because the water inlet slots are on the rear of the torpedo. Dual exhaust lower units have a vertical line of water inlets just above the torpedo.

You can use closed hub props or open hub (thru-hub exhaust) props. There is no gain or loss in performance with either prop. Now, if you want to buy a dual exhaust lower unit, they can only use props for thru-hub exhaust. The dual exhaust lower unit was developed ostensible to increase power. I don't know if it actually does--I have not yet run a comparison on the same engine. However I did use a dual exhaust lower unit on both my 150s--I had them and it couldn't hurt!

I don't know the part number but if you go to boatsdotnet they have breakdowns for almost every Force ever made. They will have the number and list it as obsolete.

Also, a couple of months back there was a thread about modifying a bellows type plate to accept a hockey puck type seal. Search for it.

 

[Boatdoc58]

No Title

Not S.O.L. on bellows seals anymore !! PM me for info. Kit includes new shift rod, seal plate (with seal installed), SS bolts, and detailed install instructions.

 

[MikeAM]

Hello Boatdoc58,
That looks like an interesting suitable substitute. What are the details on acquiring one?

 

[Boatdoc58]

Check your message box Mike.

 

[MikeAM]

Boatdoc,
I have seen the details and will call soon to place an order. Most likely I will keep it as a spare since, two or three days after my initial post I was able to locate a bellows seal and an entire seal kit for the lower unit.

I may need the seal kit when I get the new skeg welded on. Have you any experience with this? Is it better to leave the prop shaft, bearings, and gearing installed during the welding process or take it out? I have a perception that leaving it in may help prevent warping? After the welding process, replace all the o-ring seals?

 

[gregmsr]

Mind sharing where you found a bellows seal? I looked for days........gave up.

 

[MikeAM]

gregmsr

Prayer and alignment of the stars may have something to do with it. If you can find a family owned type of boat shop or marina that has been in business for 50 years or so, they have a tendency to carry obsolete parts. Since they have spent money on the parts, they are less willing to throw them away. Unfortunately, the place I found it was the last one. If there were more, I would have bought all that he had just for the purpose of helping out.

I don't know your location, but try looking in the on-line yellow pages of northern states for outboard repair shops; Akron, OH worked for me.