84 Honda BF100 lower unit rebuild.

[toqer]

I bought this motor last year for $700 from a shop mechanic. The first time I changed the lower unit oil it was milky. After I replaced it, I noticed it leaking. I took it to the outboard shop mechanic I bought it from, he charged me $130 for doing a pressure/vacuum test but said he found nothing wrong with it. It still leaked oil, and it still had milk so I decided to try and tackle it myself.

I built my own pressure tester based on plans I found here (using a lower unit fill kit adapter/bike pump) dropped the lower unit into a fishtank and at 5lb's of pressure it bubbled like a fishtank aerator from the impeller housing.

After pulling out the impeller I noticed the water seal was sort of rotten, so I pulled it out.

Under that I saw the rusted bearing. It didn't turn smooth at all, so this is what I'm trying to tackle now.

The bearing is really frozen in there good. I want to take the lower unit and put it in the oven. I have the lower unit completely disassembled except for the shift rod going into the lower unit.

So my question is, how do I disconnect the shift rod at the lower unit?

Thanks in advance!
--toqer

 

[hondon]

Re: 84 Honda BF100 lower unit rebuild.

At the gearcase end of that shiftshaft is a cogged wedge that moves a pin inside the propshaft.Unless that seal is leaking there is no need to remove that shaft to accomplish what you need to do.

 

[toqer]

Re: 84 Honda BF100 lower unit rebuild.

Thanks for the reply Hondon!

The O-Ring was leaking and Prop seal had fishing line fused into it. I want to eventually sell this motor but I'd like to make sure it's in better shape than how it came to me. Good Karma and all that. I already have all the parts I need.

I've spent most of the day trying to get the shaft bearing loose to no avail. I rented a slide hammer with a pilot bearing remover. The jaws on the pilot bearing remover didn't fit, so I took out the center of the bearing by grinding it enough to get the bearing balls out.

After that the pilot bearing attachment had good grab, but it still wouldn't budge. I did 4 cycles of butane torch, and penetrating oil to it, followed by 100 blows with the hammer each time(100x4=400 blows). These weren't maniac blows either, just some gentle tap tap tap.

I'd like to just throw everything in the oven at 200-220 degrees for an hour and see if thermal expansion will get it loose. Sorry I didn't explain that the first time, but that's why I want to remove the shift lever at the bottom unit. It simply will not fit in my oven with that long rod attached.

Thanks again!

--toqer

 

[flatheadlakemonster]

Re: 84 Honda BF100 lower unit rebuild.

I will be starting a rebuild of this exact same motor, mine is and 83, though. I will be watching this thread. Maybe we can swap advice or something in the future.....

 

[toqer]

Re: 84 Honda BF100 lower unit rebuild.

So I completely removed the lower unit per some of hondons instructions in another thread, then after some harder heat heat/pound pounding gave up and tagged out with my dad.

I'll have to confirm with my father on this, but he said he was going to lay a bead of weld on the inside of the track, then when the hot weld cools it was going to contract and take the bearing track with it. I got a call from him an hour ago saying he got it loose (I forgot to ask if that was how he did it)

Now that I know there's a viewer or two on this thread, I'll be sure to take plenty of pictures on the rest of the rebuild. I'm hoping to have this all wrapped up by Saturday so I can do an overnight trip on the sailboat Sunday/Monday.

--toqer

 

[toqer]

Re: 84 Honda BF100 lower unit rebuild.

I used a rare earth magnet to get some of the leftover grindings out. ADVICE! If you do use this method, be sure to stuff cloth or paper towel underneath the bearing to catch the metal filings.

My dad said after he applied the weld and it cooled down, the bearing track just spun in place with a screwdriver.

So now that the bearing track is out, most of the metal shavings are cleaned out of the lower unit, I'm going to start pounding the main shaft bearing back in tomorrow.

Hondo: I notice to replace the prop seal, it's got the same bearing underneath it. Is there any way of getting that bearing out without destroying it? BTW prop shaft bearing is in great shape.

--toqer

 

[hondon]

Re: 84 Honda BF100 lower unit rebuild.

That is the reverse gear bearing and there is no need to remove it to replace the propshaft seals.Carefully slide that propshaft assembly out of the carrier,then the seals are accessable for removal.

 

[flatheadlakemonster]

Re: 84 Honda BF100 lower unit rebuild.

Glad to see you are making headway, I am going to dive into mine soon!

 

[toqer]

Re: 84 Honda BF100 lower unit rebuild.

Hondon are you sure I can get that out without taking out the bearing? I'm referring to this part...

Honda part #91251-935-004

 

[toqer]

Re: 84 Honda BF100 lower unit rebuild.

It's been a while...

OK so the rebuilt went well. At least as well as it could. Turns out a lot of that stuff I was grinding out was epoxy. The lower had so much corrosion that the previous owner epoxied most of the oil seals back in.

My old man took a lathe to the corrosion / epoxy where the prop shaft exits. I made sure to use really good West systems epoxy on the rebuild.

When I put the motor in the water, not a drop came out of the lower unit! Yay! I ran 6 hours to Alcatraz and back for fleet week, and it was happy. Everything else with the lower unit is cherry too. Impeller puts out a strong stream of water, everything seems happy. OK time for the next project on this motor. Upper unit oil leak stop.

 

[flatheadlakemonster]

Re: 84 Honda BF100 lower unit rebuild.

I know this is somewhat of a dead thread, but did you get the upper leak stopped? And if so, what was it? I think I have a faulty oil filler flange/o-ring on mine that needs replacing......