Drilling out trim tilt rest bolt

spartacus · 01 September 2021, 23:14

The tilt lock bolt on my Tohatsu M60C sheared on getting the boat to Lewis during the summer. The leg was trimmed up, then lowered onto the bolt head rest.

I only noticed on arriving in Lewis. No doubt a pothole or similar, as you can hear the trailer clunk occasionally over poor roads.

Coming back, I jammed a bit of wood under the outboard between the saddle and the leg, but I've not done that for years and it seems a backward move, as I'm sure the hydraulic trim is more that robust, but there's a fair weight on the raised leg, so I wanted something to take the strain just in case.

I gave the trim and tilt a bit of a tidy tonight, so removed the upper and lower cylinder pins on the hydraulic ram so I could wire brush, grease. With the trim cylinder pins out of the way I could lift the leg entirely. It's still an odd angle to attack what's left of the bolt head with a drill.

So what I've read is drilling stainless can be done with cobalt drill bits, start slow and lube, so heat doesn't generate or it will be impossible.

I've even read you can put a soldering iron on what's left of the bolt to heat it up.

Is this a pointless exercise? I dried drilling tonight but gave up as I need new drill bits.

Any other way to support the leg when trailering?

Oldman2 · 02 September 2021, 01:35

I would be using a MIG welder to build a tit of weld and then put a nut over the tit and weld the nut on. Just the heat from the weld is sometimes enough to shock the bolt into submission, but the nut gives plenty of easy purchase. It may take 2-3 attempts before the bolt comes undone rather than the weld shear off, but ive not met one on automotive gear that didnt come out eventually like this. Plenty of release spray while the weld is very hot helps too. I dont think it matters if you only have mild wire in the welder either. Best attempted with job away from the boat or very very good sheilding to stop any red hot spatter from deflating anything! Good luck.

spartacus · 02 September 2021, 08:38

Thanks Oldman. You're probably right. I don't have a Mig welder though, and the thought of removing the outboard is a worry. We manhandled it on 10 years ago when my brother and I were younger. An engine hoist or similar would be the way to go, although I know you can raise the trailer nose to come up under the outboard, etc. I could probably shield with cheap ply boxing to avoid splatter.

If there's not a straight forward process I may just need to live with it, or look at aluminium tube I can cover with foam pipe insulation that I can thread through for when we're trailering.

jeffstevens763@g · 02 September 2021, 10:57

To be honest on my 90 Suzuki I just left it to the hydraulic trim with no issues for my 25 I use a piece of HDPE on the saddle with no issues. Pikey Dave made something for his 140 Suzuki he’ll be along soon.

wgc851 · 02 September 2021, 13:33

Quote:

Originally Posted by Oldman2

I would be using a MIG welder to build a tit of weld and then put a nut over the tit and weld the nut on. Just the heat from the weld is sometimes enough to shock the bolt into submission, but the nut gives plenty of easy purchase. It may take 2-3 attempts before the bolt comes undone rather than the weld shear off, but ive not met one on automotive gear that didnt come out eventually like this. Plenty of release spray while the weld is very hot helps too. I dont think it matters if you only have mild wire in the welder either. Best attempted with job away from the boat or very very good sheilding to stop any red hot spatter from deflating anything! Good luck.

Second that!

Jon Tallis · 02 September 2021, 14:22

You could try drilling it out (nothing ventured.....). As you say, you'll need Cobalt drills - proper professional ones from an engineering suppliers. You can order them online from www.rswww.com. they're not cheap though....
They like lots of pressure, a medium speed and lots of lube/coolant. Make sure you get the starting centre pop dead central and keep the drills square or as you get towards the diameter of the bolt, you'll be cutting into your transom bracket.
Start small, increase in small steps but be super careful with the smaller sizes - if you snap one in the hole you're stuffed.
You're unlikely to be able to drill out the threads accurately so get as large as you can then try a screw extractor. The heat generated from drilling will help free the remains.
Worst outcome is that you're no further forward so worth a go IMHO.
Good luck!

Orwell boy · 02 September 2021, 20:34

Quote:

Originally Posted by Jon Tallis

You could try drilling it out (nothing ventured.....). As you say, you'll need Cobalt drills - proper professional ones from an engineering suppliers. You can order them online from www.rswww.com. they're not cheap though....
They like lots of pressure, a medium speed and lots of lube/coolant. Make sure you get the starting centre pop dead central and keep the drills square or as you get towards the diameter of the bolt, you'll be cutting into your transom bracket.
Start small, increase in small steps but be super careful with the smaller sizes - if you snap one in the hole you're stuffed.
You're unlikely to be able to drill out the threads accurately so get as large as you can then try a screw extractor. The heat generated from drilling will help free the remains.
Worst outcome is that you're no further forward so worth a go IMHO.
Good luck!

Spot on info ,i reckon the small start min is 3mm or even 3.5 cause you need lots of pressure ,as said make sure your punch is central then go for a second drill that just under tapping size for the broken thread ,you should now find that your dot punch wasnt exactly the centre so will break through somewhere and this will prove to be your friend and will allow you to pick the thread out ,good luck

Bern Hanreck · 03 September 2021, 13:26

Just to show what's possible if you can remove the part and have the right gear and lots of patience .......

https://www.youtube.com/watch?v=kUOina5ULZo

spartacus · 03 September 2021, 17:57

Quote:

Just to show what's possible if you can remove the part and have the right gear and lots of patience ...

Indeed - a workshop and all the tools is a dream.

If you like that sort of thing, and I do, then check out Cutting Edge Engineering Australia on YouTube. Heavy duty machining, but it's all about precision. Kurtis knows his stuff.

Back to the thread - I will attempt to drill out what's left. I have carbide drill bits on order. Trouble is getting access for the correct angle so it's level. The only way to do it properly is to to remove the outboard transom bolts, the steering ram, tilt tube, the upper and lower cylinder pins which hold on the hydraulic trim, split the saddle leg and drop it off at a workshop to remove. That seems extreme!

The bolt in question is number 3.

A1an · 03 September 2021, 20:00

Quote:

Originally Posted by Bern Hanreck

Just to show what's possible if you can remove the part and have the right gear and lots of patience .......

https://www.youtube.com/watch?v=kUOina5ULZo

I’ve been a long time follower of Adam. Some of his work is absolute class. Unfortunately some of his content these days seems a bit drawn out now that he’s out on his own.

spartacus · 04 August 2024, 08:44

Just replying to my original thread (I thought I’d closed it off) as I see there’s someone in a similar position with sheared head bolts.

Anyway I got the stainless bolt off without splitting the saddle. Bought a decent set of Irwin carbide drill bits. Used centre punch, then stepped up from 3mm in increments using a little mineral oil to lube. Once hole was decent size I used a Draper screw extractor and to my surprise it just came out as it gripped. Lubed with Plus Gas too.