Lower Bearing Seal

[Yellowstone]

I am going over all of my parts and working on reassembling my 56, not 57 7.5 Fleetwin, I realized today. I think because Marine Engine only had diagrams for a 57 and I studied them so much, I thought it was a 57 for a bit before I recalled. Anyway, I’ve replaced or rebuilt the carb, ignition, and am finishing up on the gear case (water pump, seals, etc.) and putting that back together to pressure test. But I was looking at what should ride on top of the crank shaft and it appears that my lower bearing seal is damaged or at least part of the ring. Is this superficial damage or will it impact performance? I’m leaning toward paying the $25 plus a few bucks shipping I found one online. But I’m always impressed by those who’ve done this for awhile’s ingenuity in “making parts” or substitutions when appropriate. I know from the first few motors not to do things half butt. But when you can save $25 here and there, why not. Thanks for any thoughts.

[Steve D]

Yellowstone, New one on ebay for about 1/2 that or someone here might have one for less. Should be replaced as well as the o-ring and gasket.

https://rb.gy/oh5ihc

[Yellowstone]

Thanks. I will get those. I am also a little perplexed about a few things in the lower unit seal kit. #1. I see there is a Gearcase Head O-ring (18-7117 O-Ring 303360) but am uncertain about how that goes on? Second is a very small O-Ring that I don’t see in the diagram on Marine Engine: 18-7120 O-Ring 307853. Perhaps this is meant for another engine. Have tried googling it to see if it has a name/purpose without a lot of luck.

[David Bartlett]

Small O-ring is for top end of drive shaft I believe. Gearcase Head O-Ring will be apparent when you take things apart.

David Bartlett
Pine Tree Boating Club Chapter

"I don't fully understand everything I know!"

• This reply was modified 4 years, 8 months ago by David Bartlett.

[Yellowstone]

Thanks. I don’t think there’s any way I’m getting that tiny o-ring on the drive shaft. Ha. Or maybe its because I’m a beginner. Look no further than the frustrating experience I had to get the brass bushing out and replace the shift rod seal. But I know now how to do it. Anyway, it struck me after you said that its likely just replacing the one already on there?

[Yellowstone]

I was able to get the seal, gasket and O ring on ebay for about $25 including shipping. I know I could make my own gasket as some do but went the easy route. I got this motor free and a twin parts one for $20 I found a week later. I’ve invested about $180 (including this purchase) in it total replacing what chyrsleroutboarddude did in his YouTube video of a tuneup on a 55 5.5 Johnson. That has been a great resource.

[fleetwin]

Yes, that lower seal assembly must be in good condition and properly assembled on top of the driveshaft roll pin. Without it, the powerhead will slowly suck in water over time, and most likely throw a rod eventually….

[frankr]

The tiny o-ring most likely is for the shift fork pivot screw–not used on all models. Some use a gasket, some don’t even have a pivot screw.

[Yellowstone]

Thanks Fleetwin and frankr. I was kind of intimidated by this seal business at first but I thought it went well so far. This motor had a slight leak from the gear case somewhere. And it was spitting water from multiple spots up top and underneath the powerhead. I replaced two welch plugs and lined them with sealant after tapping into place. That stopped the water everywhere but from behind the shifter. I am hoping replacing the shift rod seal will have fixed that.

[fleetwin]

Yellowstone wrote:

Thanks Fleetwin and frankr. I was kind of intimidated by this seal business at first but I thought it went well so far. This motor had a slight leak from the gear case somewhere. And it was spitting water from multiple spots up top and underneath the powerhead. I replaced two welch plugs and lined them with sealant after tapping into place. That stopped the water everywhere but from behind the shifter. I am hoping replacing the shift rod seal will have fixed that.

Unfortunately, a slight water leak around the shift handle is not uncommon, the shift lever bushing gets worn in the exhaust housing and it is not replaceable. The leak might continue even after replacing the oring, I wouldn’t worry about it….

[Author]

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