Force 125 lower unit seals

[dknightfish]

I have a 1988 Force 125 Outboard. After my first trip out this year I found water in the lower unit. I dropped the lower unit and ran a pressure check several times with 10-15 psi. I did not let it sit over night, but I soaked the top end around the water pump with soapy water and the prop shaft seal behind the prop and could not see any bubbles or hear any leaks. The only problem I could see is some of the rubber on the back of the prop seal is cracked and missing. I did hit a rock and bend one blade on the prop, so maybe that damaged the prop seal. I would try a vacuum test but don?t have one of those.

Since the prop shaft seal shows some wear I figure I will start there. My question is how far do I need to disassemble the unit to change this seal? Do I have to take the forward gears out and everything? My goal is to start with the easy seals that would most likely fix the problem, and avoid taking the whole thing apart if I can. It runs and shifts smooth so I don't really need to inspect the bearings and gears, just get rid of the water in the oil.

Thanks for any suggestions.

 

[jerryjerry05]

Re: Force 125 lower unit seals

The 88 125.The seals at the fill and vent if they are the original plastic crush washers.They should be replaced.
I use Mercruiser/Mercury seals.Replace them everytime you change the oil.
If they aren't leaking I don't think I'd change them.
The drain plug on the bottom needs seal tape when installed.

 

[pnwboat]

Re: Force 125 lower unit seals

Not sure I would just replace the prop seal. I would at least replace all the seals on the prop shaft and prop shaft bearing carrier. You have to take the prop shaft assy. out and the bearings/bearings will come out as one unit. The complete seal kit is about $45. Sounds like a lot of work but once you've done it, it's not that hard. The hardest part is getting the prop shaft bearing carrier out. It's a tight fit and has to be pulled out perfectly straight. There is a special puller, but it can be done without one. Sometimes they get are difficult to get out due to corrosion.

The second hardest thing is to get the shift lever mechanism lined up and hooked up correctly. To make it easier, I take off the top plate where the water pump sits to get easier access. Since there are some seals on the plate, I just go ahead and replace them just to be sure. A word of caution when removing the top plate. Do not pry on the ends of the plate. It's thin and not really that strong and it's easy to break. Pry around the area where the water pump sits. It's a lot thicker and not as likely to break.

 

[Frank Acampora]

Re: Force 125 lower unit seals

Prop shaft seals on the one piece lower unit do not require disassembling the entire lower unit: Remove the prop, and thrust washer. Remove the anode (held with two screws.) Remove the four 1/2 inch head bolts holding the spool. Make a puller and remove the spool.

The prop shaft and gears will remain in the gear case. One caged needle bearing (rear prop shaft bearing) will remain in the spool.

Replace the two different sized O-Rings on the spool flanges. Replace the prop shaft seal. Reassemble. When reassembling, be certain that the two half circle clips are seated in the groove in the gear case. These actually lock everything in. If they are not seated, it is possible to lose the whole gear pack in reverse operation.

Another common source of water infiltration is the shift rod seal. If the seal looks good, it can be pressed further into the case by using an appropriately sized socket and a piece of pipe as an extension. Tap with a hammer until it is snug around the shift rod. To completely replace it requires removing the top plate. Use a lag screw to pull the old one and press in the new with the steel side up..

 

[dknightfish]

Re: Force 125 lower unit seals

Thank you everyone for your replies, the knowledge of people on this forum is outstanding.

I have not been using tape on the drain plug or replaced the plastic washers since I bought the boat, so I will try that and take it for a run. If I'm still getting water in the unit I will get the seal kit and replace the o-rings and seals, you guys make it sound a lot easier then the book. I was hoping I did not need to take all the gears out, re-shim the gears and all that stuff.

Thanks again.

 

[stubtail]

Re: Force 125 lower unit seals

You mentioned that you had a prop strike. It is doubtful, but maybe you have bent the propshaft. Should that be the case, water may be allowed to enter the LU between the shaft and an otherwise serviceable seal. Check the runout of the shaft to ensure it is not bent.

 

[jerryjerry05]

Re: Force 125 lower unit seals

Profile?? Location? You might be close to someone who can help??