Freezing lower unit

[fleetwin]

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

Well, I would have thought that the 28hp gear housing part number would have superceded to the 33hp housing…  So many questions, probably over thinking it as usual.  Try to have a look at that water passage coming up from the water screen looking for cracks, as Frank has described.

I would definitely replace the SS impeller housing though, and make sure the aluminum impeller hsg is flat.

[bob-d]

Dave, good thought about the JB Weld. I am going to try that on the ice damaged case.
On my replacement case I’m just going to pull it off at the end of the season, and store it in a heated area. A bit of a hassle but I guess the safest solution.

Don, although you can probably bolt up a complete 33 case to a 28, it doesn’t look as the internals are interchangeable.
Especially looking at the pinion gear area. 28 on left, 33 on right. So I don’t believe a bare 33 case would have worked in my case.
Again hard to tell exactly without both cases in front of you.
Thank again,
Bob D

[crosbyman]

one cause of  freezing GC  is likely  the accumulation of  crud, sand  & whatever   blocking drain hole (s)

When I fixed up a Merc  2-3 years ago,    this what I found in the plugged up GC  …. the lower drain  hole  was totally blocked  but luckely  the  previous owner  probably stored it inside …saving the GC  from expanding

Anytime impellers are  changed,    a good  air/water blast  in  (non oiled)   accessible lower cavities  should always    be  the way to go.

 

btw… cheap Dollarstore  doggy poop pads  are great for catching oily drips …. and  sand  🙂

 

Joining AOMCI has priviledges 🙂

1 user thanked author for this post.

bob-d

[Finn Freeman]

bob-d wrote:

Don, although you can probably bolt up a complete 33 case to a 28, it doesn’t look as the internals are interchangeable. Especially looking at the pinion gear area. 28 on left, 33 on right. So I don’t believe a bare 33 case would have worked in my case. Again hard to tell exactly without both cases in front of you.

The same thing is true between the 25/30hp gear case of 1956 and earlier, and the 35hp gear case from 1957.

From my understanding, omc gearcases for <30hp use the short pinion, and >30hp use the long pinion.

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bob-d

[fleetwin]

OK, I do see the two different style pinion set ups.  The one on the right uses the spring/ball clutch dog system as well.    I don’t have a parts breakdown for a 56 30hp, would be interested to figure out if it uses the same gear housing as the 33hp.

Hoping the replacement housing has some sort of drain/relief holes in those two blind cavitities.

[jeff-register]

Crosbyman,

Can’t believe how much sand etc you removed, great idea!! Also seems the pinion area was improved for more support & sealing, Little improvements heee & there.

1 user thanked author for this post.

frankr

[bob-d]

Don, just wanted to follow up with a final update to this long / old post.
Frank wins the prize on this one!
Bill W was nice enough to find me a good used gearcase, which solved the overheating problem. Apparently the ice damage under the impeller plate  in the blind cavities impeded the flow of water to the impeller.
The new gearcase pumps like a champ. Before I mounted the “new” gearcase I ran a garden hose to the brass pickup tube in the lower unit to check the flow through the powerhead . Everything was fine so I started the motor. It stayed within normal operating temperature, so I knew there was no blockage in the head. Wish I would have done that before I pulled  apart the head last summer!
Hope the post helps someone in the future with a strange overheating condition.
Thanks again to all the members who contributed ideas trying to solve the problem.

Bob D

[fleetwin]

Cool!

[joecb]

I can’t comment on the damage in bob-d motor, but I will say that there are a couple of big cavities in the typical OMC lower unit that drain through rather small and easily plugged holes. I have had to literally drill out compacted crud from these cavities in order to ensure free passage. Inspect the outside of the lower down near the gear case, look for any small ( 1/8″ ) holes, free communication to these holes from internal cavities is critical in preventing freeze damage.

Joe B

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bob-d

[Author]

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