Topic: Freezing lower unit – Antique Outboard Motor Club,Inc

This topic has 18 replies, 9 voices, and was last updated 5 months ago by joecb.

Viewing 10 posts - 1 through 10 (of 19 total)

1 2 →

Author

Posts
September 12, 2023 at 12:23 pm #280515
bob-d
Participant
US Member
Does anyone know how to prevent freeze damage in your lower unit?
Here is a picture of my 28HP lower unit that didn’t pump properly this summer. Frank diagnosed it as freeze damage. I usually drain and refill the lower unit oil when I winterize, but that’s all I do to the lower unit.
How do you get all of the water out of the pockets underneath the impeller plate? I guess I could just drop the unit and bring it into a heated area? As Fleetwin suggested previously always put some 847 on the plate when you service your impeller, but will that seal out all water intrusion?
Never had this problem before with smaller HP motors who sit in the same garage with freezing temps over the winter.
Thanks,
Bob D
September 12, 2023 at 1:28 pm #280519
frankr
Participant
US Member
In your particular case, the damage came from water freezing in enclosed cavities with no drainage or outlets. The water seeped into those cavities over a period of time. I know of no way to prevent that.
September 12, 2023 at 2:46 pm #280524
bob-d
Participant
US Member
Thanks Frank, that’s what I was afraid of. Strange design for us northern boaters.
I guess I will just drop it, and bring it inside after each season.
28’s cases are sort of a weird duckling, and hard to find, with not a lot of interchangeability. The few I saw on EBay had the same damage as mine.
Bill W generously (thanks again Bill) found a replacement case for me, so I definitely don’t want to screw that one up.

Bob D
September 12, 2023 at 3:08 pm #280525
mike n
Participant
US Member
As precaution i winterize my motors by flushing them with RV antifreeze. Not sure if that helps

mn

1 user thanked author for this post.

bob-d
September 12, 2023 at 9:55 pm #280548
fleetwin
Participant
US Member - 2 Years
Hmmm, this is an interesting topic indeed. The way I see it, those cracks didn’t create an air leak into the pump, because the outer diameter of the SS impeller housing is sealed from air/exhaust. I’m guessing that the cracks caused the top of the casting to be uneven/not flat, which distorted the SS impeller plate, which may have created an air leak between the bottom side of the impeller plate and gear housing outer diameter mating surfaces. I would definitely replace the SS impeller plate, it may have been distorted from the bad fit.

I’m not recommending this, just theorizing here. What would be the harm in drilling relief holes through the bottom of those sealed cavities?? Again, those cavities are sealed from the water passages underneath the impeller plate, so their would be no air leak. Any water inside those sealed cavities would drain out once the engine is out of the water….

Perhaps you new g/c housing might have these relief holes already…

What do you think Frank??
September 12, 2023 at 10:06 pm #280550
frankr
Participant
US Member
I think your reasoning is sound. But as I recall the original conversation, I was speculating there might have been additional cracks somewhere between the inlet screen and water pump, allowing exhaust to enter the path to the pump. Bob said he didn’t find any and we sort of left it there.
September 12, 2023 at 10:52 pm #280554
bob-d
Participant
US Member
Don, I didn’t get the replacement case from Bill W. yet.
When it arrives, I will definitely update the post, and shoot a few pictures to let you know if it has holes.
I really doubt it, as Frank said previously that he saw this freeze damage before on northern motors that were brought down south, so I guess it’s not an isolated case.
OMC only made the 28HP from 62-64 with the proprietary gear case part number.
Possibly with the evolution to the 33HP gearcase in 65 (different part number) they changed the case to eliminate non draining casting cavities?
Wondering if there was ever a service bulletin possibly to provide a few relief holes?
So many questions??
Thanks,
Bob D
September 12, 2023 at 11:01 pm #280555
dave-bernard
Participant
US Member
how about filling the cavities with J-B weld?????
September 13, 2023 at 8:51 am #280563
fleetwin
Participant
US Member - 2 Years
frankr wrote:

I think your reasoning is sound. But as I recall the original conversation, I was speculating there might have been additional cracks somewhere between the inlet screen and water pump, allowing exhaust to enter the path to the pump. Bob said he didn’t find any and we sort of left it there.

Ah yes, forgot about that possible issue.
September 13, 2023 at 8:55 am #280564
fleetwin
Participant
US Member - 2 Years
bob-d wrote:

Don, I didn’t get the replacement case from Bill W. yet.
When it arrives, I will definitely update the post, and shoot a few pictures to let you know if it has holes.
I really doubt it, as Frank said previously that he saw this freeze damage before on northern motors that were brought down south, so I guess it’s not an isolated case.
OMC only made the 28HP from 62-64 with the proprietary gear case part number.
Possibly with the evolution to the 33HP gearcase in 65 (different part number) they changed the case to eliminate non draining casting cavities?
Wondering if there was ever a service bulletin possibly to provide a few relief holes?
So many questions??
Thanks,
Bob D

I wonder why the gear hsg would be unique to the 28hp?? Seems like the same gear housing would be used from mid 50s up on this style engine. Certainly the 28 and 33hp models would use the same hsg… Who knows, those part numbers are strange also.
Author

Posts