Topic: ’56 Big Twin LU drain passage plugged – Antique Outboard Motor Club,Inc

This topic has 7 replies, 7 voices, and was last updated 9 years, 7 months ago by mas.

Viewing 8 posts - 1 through 8 (of 8 total)

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October 2, 2015 at 4:20 pm #2684
wet-willie
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Can some one tell me what diameter drill I should use, or an easier way, to clean the drainage port on the lower unit of my Big Twin?
I ran an 1/8" drill bit in the outlet. That was easy. I’ve been using a long 1/8" bit from on top and its been extremely slow going. I’m hoping there’s a better way or if I should be trying to do this at all.
October 2, 2015 at 5:48 pm #25008
1946zephyr
Participant
Those are usually plugged from years of corrosion in there. It’s very difficult to clear it up and get it draining correctly.
Unfortunately, past owners have not kept those clean and this is what we end up with. The factory designed these older motors with too small of holes and they plug up easy. You’ll notice that a lot of newer motors doubled the size of those drain holes, so there is far less chance of plugging up.
October 2, 2015 at 7:10 pm #25009
fastjohn
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US MEMBER PAY BY CHECK
I have this problem with most OMC motors from this era. Some drain passages were packed so tight, it seemed like concrete. I normally use a long standard drill bit to open them( by drilling from the top down and measuring as I go to prevent drilling too deep) but have had to resort to a carbide tipped drill bit on occasion when a regular bit would not touch it. Make sure you drill straight, it is easy for your bit to wander and drill into the oil cavity–don’t ask me how I know.
October 2, 2015 at 7:20 pm #25010
vintin
Participant
Once you get it cleaned out I’ve found I can push a piece of weed eater plastic string up from the bottom to keep it opened up. Just bend the end pointing the way you want it to go and push using pliers.
October 2, 2015 at 8:43 pm #25016
wiscoboater
Participant
Can someone post a picture of this passage, or where it is located? This is good information to know. I have a couple of big twins I will be working on this winter and would like to check this on them

Thanks,
Wannabe
October 2, 2015 at 9:42 pm #25022
chris-p
Participant
When those mud dauber nest harden, the poster above is correct, its like drilling through concrete! Very slow going sometimes.

This is a real problem, as the water will stay pooled in the gearcase cavities, and then freeze and expand, cracking the case in the winter.

Wannabe, look for small little 1/8" holes on the outside of the case. Those are them, unless someone unknowing plugged them. Ive seen that.
October 3, 2015 at 2:46 am #25034
mas
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US Member
Been there, done that! I got lucky and found the original passage in my ’57 Lark after drilling through some tough material. If i remember right, I used a long 1/4 inch bit!
October 3, 2015 at 2:53 am #25035
mas
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US Member
That was several years ago…maybe 3/16????
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