seawater pump bracket adjustment bolt broken

[saltylcd]

good morning all,

I made a big mistake yesterday when trying to adjust the water pump belt tension on my yanmar 3HMF.
I applied too much leverage on the adjustment bolt and broke the very end of the bolt deep inside the engine block...
There is no way to see the broken piece at the very end of that hole, so any attempt to drill/extract would be totally blind.
A mechanic is quoting me 6 up to 10h to remove a couple of components to get to the broken piece and remove it without going blind.
Could a cheaper solution be to attempt re-threading the first part of the whole and use a different type of bolt?
I read about using epoxy to fill in the hole, push in new bolt, let it set and then unscrew the bolt leaving a new thread...

what would you do?

[Compass790]

I doubt that epoxy will work in the way you hope in that situation. It would break again.
Doesn't sound like you are mechanically inclined so not sure if this idea will help you.
Look to see how tension is applied to the belt & see if you can make up a bracket using a different anchor point & a rigging screw/turnbuckle type tensioner.
I'm not familiar with your motor so this is just a general idea.

[Wotname]

Ohh... you are in a world of hurt! The proper way is to remove the front gear housing in order to get at the broken piece of thread. Anything less is a gamble - are you feeling lucky?

Here are a couple of screenshots from the parts book should other posters have better ideas. One of the gear housing M8 bolts #22 (fig 3) has broken where it is tapped into the block.

[jimbunyard]

I'd evaluate the situation and get a left handed drill bit either slightly smaller than the hole in the timing/governor cover, or if the bolt is a shoulder bolt and has a smaller thread diameter than the 'shoulder', get the largest L/H bit that the thread diameter will allow, wrap aluminum duct tape around it to form an impromptu drill jig bushing (to almost match the shoulder diameter [careful to wrap it the right way!]), and see if the reverse drilling torque will wind the stub out. It often will.

Otherwise, you're stuck with dissassemblng the front cover. Epoxy, if it works at all, will be very short-lived, and then you've gotta deal with that, in addition to the broken bolt.

This is of course assuming that the bolt hole is through a boss in the cover, so that no metal swarf will be introduced into the interior of the engine.

[Wotname]

FWIW, those bolts are about 4" long so if you try the LH drill approach, make sure the shank is long enough.

[Scubaseas]

Saltylcd
This is the adjustment bolt, not the pivot bolt yes?


Did the bolt break on tightening or loosening? If tightening a left hand drill bit would be my first choice. You may have to weld an extension on it to get the depth needed. If it broke on loosening take the timing cover off.

Retapping the case might work as there is not a ton of pressure but if wrong you will crack the case which I bet is more than expensive. Plus leave you with a huge hole leaking oil all over. 10mm and use a stud but you would have to enlarge the slot in the mounting plate or have a 10mm X 8mm stud made. Or slot the end of the stud.

I would be more comfortable making a bar to run from one of the top bolts to the bracket.

You could mount an electric pump off the engine.


Me? If it didn't come out with the left hand bit I'd pull the cover and fix it the right way. If I had to get home I'd use any of the above or just jam something under it for belt tension. Or use the electric pump I have until I could fix it proper.

[saltylcd]

Thank you all for your inputs so far.

Sounds like anything related to re-threading (with epoxy or thread insert) is a bad idea, so I will stay away from that approach.

Regarding taking the timing cover off, we're talking about the whole timing gearcase, right?
How tricky is this?
I usually do everything on my boat and have the full shop manual for my engine, but wondering if this is beyond my skill set and could make an even bigger mess (but could really use the $$ saved by not hiring a mechanic...)

[Cheechako]

You need 1-1.5 of thread diameter in steel. Do you have that much and could just use a shorter bolt?
So if the bolt is say 5/16" you need 5/16' to maybe 3/8' of thread depth

[Cheechako]

Originally Posted by Cheechako

You need 1-1.5 of thread diameter in steel. Do you have that much and could just use a shorter bolt?
So if the bolt is say 5/16" you need 5/16' to maybe 3/8' of thread depth

never mind, it is a long smooth shank bolt I see from your diagram. How in the world do you break it off that deep in? It must be from tightening not leverage.

[Scubaseas]

If you broke the bolt on tightening it should come out easily with a left hand drill bit. Or if that doesn't work with an easy out. But either way you may have to weld a rod or extension on to either the drill bit or the extractor.

[saltylcd]

I decided to do it the right way and remove the timing gearcase to get to the broken bolt.
After removing the crankshaft pulley, I'm running into an issue with the drive key - I can't it out of the shaft.
I applied some PB blaster but still no luck...Any tips?

[Scubaseas]

Leave it alone. It can stay where it is. Normally a brass drift/punch or for the more brutal a cold chisel and tap it loose.. Use Permatex Ultra Gray or Ultra Black as a THIN coat on both sides of the gasket. No gobs oozing out please maybe find a youtube video. Try not to get any shavings (bolt or gasket) into the crank case.