1971 100HP problems Broken & Stuck bolt

Don S.

Cadet
Joined
Aug 14, 2007
Messages
15
Hello All, I have done some searching, but nothing really addressed this issue I am having.

Both My Outter exhaust cover and Inner Exhaust cover gaskest were leaking. Outter was leaking excess oil down onto the Lower unit. Decided to pull the bolts and fix this problem. To say the least I have opened a Can of worms. I now have 6 Grade 5 1/4-20 Bolts that broke off, and one 10-24 Stainless steel Machined screw that have broken.

The issue is the inner exhaust gasket was leaking onto the center bolts and had rusted them in place. From the looks of it this motor has never been apart, i.e. 36 years of neglected service possibly.

The issue being, that these bolts broke while trying to remove them and it seems that the rust has seized them in the holes. I have used a punch to ping them to gt them loosened. Kroil oil saok for a week. I have drilled them up to 3/32 hole all the way through. Tried Easy outs, Vise Grips, and nothing so far has worked. I am a little weary to use heat 1.) Beacuse of possible melting of the aluminum alloy. 2.) Possibly changing the crytaline struckture of the alloy and making it soft, or possibly brittle. 3.) This is the exhaust are and is coated with oil and some carbon build up, kind of afraid of igniting this stuff.

I have ran out of patients and have been at this issue for the last month. Seems about the only solution is to have a machine shop get them out, Cause most other outboard mechanics where I live won't touch this vintage. I am seeing now why that may be so.

Just a little history, I bought the outboard and 1979 16' Marlin with a 92 easy loader trailer for $800 bucks not running. Which before this issue I had got it running pretty good.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 1971 100HP problems Broken & Stuck bolt

Can you get the vice grips on the stubs? If so, heat the aluminum till it expands and loosens it's grip on the bolt, then go ahead and take it out. You won't hurt the aluminum unless you melt it. Being an old salt-water mechanic, I've done them thousands of times.

Can't get vice grips on? Then heli-coils are a gift from God. But it takes a lot of practice and skill to drill out the old screw. Novices will mess up a few dozen times before getting the hang of it. Untill then you will break drills, break taps and get the drill off into the soft aluminum. None of those is good.

Throw away those easy outs. There is no such thing. They aren't easy and they won't get the screw out. But they WILL break off in the screw and then you are out of luck. You can't drill an easy out out. Neither can you drill out a broken drill bit....or a tap.
 

NgtvNrg

Seaman Apprentice
Joined
Apr 30, 2007
Messages
49
Re: 1971 100HP problems Broken & Stuck bolt

I had a bolt break on the head changing the water deflectors. I tried every thing you have to no avail. After breaking several drill bits I got a tungsten carbide cutter for my Dremel and ground the bolt out from the inside.
 

Don S.

Cadet
Joined
Aug 14, 2007
Messages
15
Re: 1971 100HP problems Broken & Stuck bolt

Well I have lost my patience, which if you want to actually fix something is good. SO I am just going to drag it over to a machinist I know and have him take a crack at it. I would rather admit defeat, than have someone tell me "Oh you shouldn't have done that, I can't fix that".

Thanks for the help guys.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 1971 100HP problems Broken & Stuck bolt

Yeah, one of the most profound statements my Dad ever made was "If somebody else can do it, by !#%^&#, so can I". I've lived my life by that philosophy.

But 40 years later I was in deep trouble from taking on an impossible job and Dad told be to get somebody else to do it. I reminded him of what he'd told me so long ago and he pondered a moment and said "yeah, but sometimes somebody else can do it better".

I miss my Dad.
 

Don S.

Cadet
Joined
Aug 14, 2007
Messages
15
Re: 1971 100HP problems Broken & Stuck bolt

My dad is still around, the unfortunate part is that I wasn't around in his days of racing boats. He used to rebuild outboards at a shop on side and build racing OB to race. IIRC he used to use I think mostly Merc. 30H OB running a quicksilver L/U and other tricks to hop up the motor. I say unfortunate cause he forgot more about working on outboards, than most OB mechanics in the our area know about fixing them.
 
Top