wrote
One possibility is that those "thread" in the old water pump base may
not be "real" thread. They may be a corroded surface that mirrors the
thread in the bolt.

IOW, corrosion formed around the bolt threads creating something that looks
like a threaded hole. That sounds plausible enough for me.

Do we need to re-apply the heli-coil insert whenever we
replace the bolt (like when we need to replace the impeller)?

The coil will probably stay in there forever. I suppose it's possible for it
to back out when you remove the bolt, but I've never seen it happen.

wrote:
:I over-torqued four bolts in the lower unit of an outboard, and the
:heads of three bolts broke off. I managed to remove one of the broken
:bolt using a Dremel tool and a diamond grind bit. But I cannot remove
:the other two broken bolts using the Dremel tool. Based on the past
osts in this newsgroup, I learn that the best option in this situation
:is to drill out the broken bolts. I would like to learn the details of
:the way to drill out the broken bolts. My question is:

:Which size of drill bit do I need? Should it be as large as the hole
:where the broken bolt is?

The best way to do this is to get a selection of left-handed drill
bits. These have the twist going the opposite way from a normal twist
drill. You have to run your drill in reverse to drill a hole with one
of these. That means, in addition to puting a hole in the bolt, you
apply some anti-clockwise force to the bolt, which may back it out.
Start with a small bit; drill exactly in the center, exactly
perpendicular to the hole. Then move up to a bigger bit, and repeat.
Increase the size of the bit until you're using a bit the size of the
minor diamter of the bolt (the diameter of the round part of the
bolt, minus the threads.). Then you can use a pick to pick the
threads from the bolt out of the threads in the hole. You could also
drill a hole, and try an EZ-out.

There's a better description he
http://www.dimebank.com/tech/BrokenBolt.html

:Related questions:

: The bolts are for securing the water pump housing for the
:impeller. The hole for the bolt is at the edge of the water pump base
:-- meaning that one side of the hole is kind of thin -- something like
:3/32" thick. The bolt itself is like 1/4" or slightly larger. Because
:I have over-torqued the bolts, I found that the holes pretty much losed
:most of the thread. If I drill out the bolts, I probably will find
:that the holes will become even larger. If I re-thread the hole after
:drilling out the bolts, I am afraid that the holes will be even larger.
: I am afraid that there will not be enough metal left. Is my
:estimation correct? I am wondering whether I may be better off somehow
ouring in new metal into the holes and drill new holes instead of
:rethreading/enlarging the existing holes?

There are thread inserts, called heli-coils (that's the brand name of
the original, and best, there are others), that may solve this problem
for you. The hole needs to be drilled oversize, roughly to the major
diamter of the hold hole, and then it's tapped for the insert. The
insert is a coild of wire that allows the use of the original sized
fastener.

David

If he's worried about how much metal is left then helicoils are
probably out of the question.

The most important thing is to try very hard to drill down the center
of the remaining bolt. It helps to grind the top flat and center punch
before drilling. The surrounding metal in this case is far softer than
the bolt so getting off center will be a big problem.

Sometimes it is hard to use easy outs on smaller bolts because they
tend to spread the bolt material out further jaming it in the hole.

Sometimes I've been able to find a metric size that is slightly bigger
than the american size and tap the hole to the metric size
successfully. This is usually closer than the next size up america
size.

It is pretty hard to get anything into the hole to replace missing
metal since I'm thinking you are working with cast aluminum. If it
gets that bad then maybe securing threaded studs into the holes with
epoxy might be worth a try. Particularly if there is some thread left.
Then use nuts to secure the water pump.

David Scheidt wrote:
wrote:
:I over-torqued four bolts in the lower unit of an outboard, and the
:heads of three bolts broke off. I managed to remove one of the broken
:bolt using a Dremel tool and a diamond grind bit. But I cannot remove
:the other two broken bolts using the Dremel tool. Based on the past
osts in this newsgroup, I learn that the best option in this situation
:is to drill out the broken bolts. I would like to learn the details of
:the way to drill out the broken bolts. My question is:

:Which size of drill bit do I need? Should it be as large as the hole
:where the broken bolt is?

The best way to do this is to get a selection of left-handed drill
bits. These have the twist going the opposite way from a normal twist
drill. You have to run your drill in reverse to drill a hole with one
of these. That means, in addition to puting a hole in the bolt, you
apply some anti-clockwise force to the bolt, which may back it out.
Start with a small bit; drill exactly in the center, exactly
perpendicular to the hole. Then move up to a bigger bit, and repeat.
Increase the size of the bit until you're using a bit the size of the
minor diamter of the bolt (the diameter of the round part of the
bolt, minus the threads.). Then you can use a pick to pick the
threads from the bolt out of the threads in the hole. You could also
drill a hole, and try an EZ-out.

There's a better description he
http://www.dimebank.com/tech/BrokenBolt.html

:Related questions:

: The bolts are for securing the water pump housing for the
:impeller. The hole for the bolt is at the edge of the water pump base
:-- meaning that one side of the hole is kind of thin -- something like
:3/32" thick. The bolt itself is like 1/4" or slightly larger. Because
:I have over-torqued the bolts, I found that the holes pretty much losed
:most of the thread. If I drill out the bolts, I probably will find
:that the holes will become even larger. If I re-thread the hole after
:drilling out the bolts, I am afraid that the holes will be even larger.
: I am afraid that there will not be enough metal left. Is my
:estimation correct? I am wondering whether I may be better off somehow
ouring in new metal into the holes and drill new holes instead of
:rethreading/enlarging the existing holes?

There are thread inserts, called heli-coils (that's the brand name of
the original, and best, there are others), that may solve this problem
for you. The hole needs to be drilled oversize, roughly to the major
diamter of the hold hole, and then it's tapped for the insert. The
insert is a coild of wire that allows the use of the original sized
fastener.

David

David Scheidt wrote:
wrote:
:I over-torqued four bolts in the lower unit of an outboard, and the
:heads of three bolts broke off. I managed to remove one of the broken
:bolt using a Dremel tool and a diamond grind bit. But I cannot remove
:the other two broken bolts using the Dremel tool. Based on the past
osts in this newsgroup, I learn that the best option in this situation
:is to drill out the broken bolts. I would like to learn the details of
:the way to drill out the broken bolts. My question is:

:Which size of drill bit do I need? Should it be as large as the hole
:where the broken bolt is?

The best way to do this is to get a selection of left-handed drill
bits. These have the twist going the opposite way from a normal twist
drill. You have to run your drill in reverse to drill a hole with one
of these. That means, in addition to puting a hole in the bolt, you
apply some anti-clockwise force to the bolt, which may back it out.
Start with a small bit; drill exactly in the center, exactly
perpendicular to the hole. Then move up to a bigger bit, and repeat.
Increase the size of the bit until you're using a bit the size of the
minor diamter of the bolt (the diameter of the round part of the
bolt, minus the threads.). Then you can use a pick to pick the
threads from the bolt out of the threads in the hole. You could also
drill a hole, and try an EZ-out.

There's a better description he
http://www.dimebank.com/tech/BrokenBolt.html

:Related questions:

: The bolts are for securing the water pump housing for the
:impeller. The hole for the bolt is at the edge of the water pump base
:-- meaning that one side of the hole is kind of thin -- something like
:3/32" thick. The bolt itself is like 1/4" or slightly larger. Because
:I have over-torqued the bolts, I found that the holes pretty much losed
:most of the thread. If I drill out the bolts, I probably will find
:that the holes will become even larger. If I re-thread the hole after
:drilling out the bolts, I am afraid that the holes will be even larger.
: I am afraid that there will not be enough metal left. Is my
:estimation correct? I am wondering whether I may be better off somehow
ouring in new metal into the holes and drill new holes instead of
:rethreading/enlarging the existing holes?

There are thread inserts, called heli-coils (that's the brand name of
the original, and best, there are others), that may solve this problem
for you. The hole needs to be drilled oversize, roughly to the major
diamter of the hold hole, and then it's tapped for the insert. The
insert is a coild of wire that allows the use of the original sized
fastener.

David

As mentioned in my other reply, I have removed the broken bolts by
simply removing the water pump base. And I also attempted to drill out
the broken bolt; but I could not get the drill bit to center on the
bolt because the bolt was sunk inside the hole and I could not see the
surface of the bolt that well. This ended up messing up the thread of
the hole. Hopefully, the heli-coils will fix this problem. Thanks.

Anyway, I will bring the lower unit to a marine mechanic later in this
afternoon, and I will see how he will fix the thread in the hole.

Jay Chan

Finally, a copy of the Mercury Service Manual arrived last night.

AWWWW! had to go and spoil all the guessin' fun by goin to the book!
Well good for you! At least you got to where you wanted to be. As for
the hogged out hole, this looks like an opportunity for "JBWeld to step
up to the plate. Clean the daylights out of that hole, I mean REALLY
clean it! Mix up enough of the A part, and B part to fill up the entire
threaded hole. (from your description it goes entirely thru the
casting?) if so that is great. Working from the BACK side of the
casting will guide you. After the JB sets drill in the EXACT CENTER
with a small pilot drill, 1/8 or smaller, then when satisfied you have
a good center, drill with the tap drill taking all the time you need. A
drill press would be handy for the previous steps. Hand tap then,
backing out very often, and try to pick up the original threads.
Carefully run your tap thru. As an afterthought somewhere I have LO
temp ALUMINUM stick, that I tried to use to plug a tank hole
unsuccesfully. Did melt the stick, but I did not have enough heat to
have it fuse to the sheet. Was using a propane torch. With your
casating you might have a similar problem. If there are better ways to
recover from the situation, we will soon hear about them. maybe
another member has a better recommendation

Den 48tfYF

den wrote:
Finally, a copy of the Mercury Service Manual arrived last night.

AWWWW! had to go and spoil all the guessin' fun by goin to the book!
Well good for you! At least you got to where you wanted to be. As for
the hogged out hole, this looks like an opportunity for "JBWeld to step
up to the plate. Clean the daylights out of that hole, I mean REALLY
clean it! Mix up enough of the A part, and B part to fill up the entire
threaded hole. (from your description it goes entirely thru the
casting?) if so that is great. Working from the BACK side of the
casting will guide you. After the JB sets drill in the EXACT CENTER
with a small pilot drill, 1/8 or smaller, then when satisfied you have
a good center, drill with the tap drill taking all the time you need. A
drill press would be handy for the previous steps. Hand tap then,
backing out very often, and try to pick up the original threads.
Carefully run your tap thru. As an afterthought somewhere I have LO
temp ALUMINUM stick, that I tried to use to plug a tank hole
unsuccesfully. Did melt the stick, but I did not have enough heat to
have it fuse to the sheet. Was using a propane torch. With your
casating you might have a similar problem. If there are better ways to
recover from the situation, we will soon hear about them. maybe
another member has a better recommendation

Den 48tfYF

I have brought the lower unit to a marine mechanic, and he will use a
coil insert to repair the messed-up-threaded hole. Thanks anyway.

Hopefully, someone else has a similar problem will be able to take
advantage of your suggestion.

Jay Chan

I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit you
over the head about the rest of them?

-W



wrote in message
ups.com...
I over-torqued four bolts in the lower unit of an outboard, and the
heads of three bolts broke off. I managed to remove one of the broken
bolt using a Dremel tool and a diamond grind bit. But I cannot remove
the other two broken bolts using the Dremel tool. Based on the past
posts in this newsgroup, I learn that the best option in this situation
is to drill out the broken bolts. I would like to learn the details of
the way to drill out the broken bolts. My question is:

Which size of drill bit do I need? Should it be as large as the hole
where the broken bolt is?

Related questions:

The bolts are for securing the water pump housing for the
impeller. The hole for the bolt is at the edge of the water pump base
-- meaning that one side of the hole is kind of thin -- something like
3/32" thick. The bolt itself is like 1/4" or slightly larger. Because
I have over-torqued the bolts, I found that the holes pretty much losed
most of the thread. If I drill out the bolts, I probably will find
that the holes will become even larger. If I re-thread the hole after
drilling out the bolts, I am afraid that the holes will be even larger.
I am afraid that there will not be enough metal left. Is my
estimation correct? I am wondering whether I may be better off somehow
pouring in new metal into the holes and drill new holes instead of
rethreading/enlarging the existing holes?

The other thing is that there is supposed to have a gasket on top
of the surface. I am wondering if I rethread and enlarge the holes,
there may not be enough metal at the edge of the water pump base to
bite into the gasket and prevent water from getting into the bolt. Is
this something that I need to worry about?

Thanks in advance for any info.

Jay Chan

"Clams Canino" wrote in message
news

I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit you
over the head about the rest of them?

-W


He broke the first two ... first.

Eisboch

"Eisboch" wrote in message
...

"Clams Canino" wrote in message
news

I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit
you
over the head about the rest of them?

-W


He broke the first two ... first.

Eisboch


I know this because it's something I would do .

Kibosh

"Clams Canino" wrote in message
news

I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit you
over the head about the rest of them?

-W


I was wondering the same thing. ;-)