Stuck lower unit bolts.

[steviecops]

Hi<br />In a few weeks time, I'm going to overhaul the water pump on my engine. As I've read on here that some of the bolts can be a job to get out, today I tried them all to see if I would have problems when I come to drop the lower unit.<br /><br />The two bolts that hold the trim tab came out easily, but I couldn't get any movement on any of the four which hold the lower unit on. They don't look corroded on the outside, and are still shiny silver.<br /><br />Is there anything I can do to try to loosen these four bolts over the next few weeks? I really don't want to have to use brute force if I don't have to, and using heat scares the hell out me!<br /><br />I've given them all a good squirt with penetrating oil, but as you can imagine, I can't get it to soak in as the bolts face downwards! There isn't enough room between the bolts and the cavitation plate to use an impact wrench either.<br /><br />I was thinking of moulding some clay or something into a bowl around the bolts and filling them with the penetrating oil, in the hope that capilliary action might get some onto the threads. Is this my best bet, or are there other tricks of the trade that can be employed?<br /><br />As I've said, I'm in no hurry and am prepared to try to persuade the bolts out over a period of a few weeks, rather than force them and have to drill them out. Any help and advice will be gratefully acepted.<br /><br />Thanks <br />Steve

 

[OBJ]

Re: Stuck lower unit bolts.

The clay sounds like a good idea Steve. A hand held impact wrench may also be of help. Let them soak for a while or days and then give them a wrap with the impact. Heat would be another way to go but if you don't have to use it, don't.

 

[steviecops]

Re: Stuck lower unit bolts.

Thanks OBJ. I'll give the clay a try.<br /><br />I'm not familiar with impact wrenches. Would there be room to use one between the bolts and the cavitation plate? There is only a gap of about 3-4 inches to play with.<br /><br />Thanks again<br />Steve

 

[jim dozier]

Re: Stuck lower unit bolts.

Don't be afraid to apply heat. You can't really go very far with outboard repair until you get comfortable with it anyway. Stuck bolts are part and parcel of working on outboards in the marine environment. If you use a propane torch, which is adequate for most problems, you will not be able to melt the aluminum. Although I have read different opinions on the advantages of heating the surrounding casting versus the bolt itself, if you stick with the propane it probably doesn't matter. Most serious mechanics get comfortable with oxyacetylene with the caveat that you must be careful not to overheat the casting.<br /><br />The point in heating is to expand the metals which have dissimilar expansion rates and then let them contract on cooling. The differential movement helps to break loose corrosion and allow the bolt to be loosened. It also creates more space for penetrating oils to get in there by capillary wicking. I personally believe you should wait till the bolt is cool before you start twisting it.<br /><br />Get a propane torch and have at those suckers.

 

[steviecops]

Re: Stuck lower unit bolts.

Well the little bowls have been moulded in place and are now full of penetrating oil. I'll leave them like that for a few days and try again to shift the bolts.<br /><br />I feel a little happier knowing that I won't be able to melt the aluminium with propane, so if it comes to it, I will have a go with heat. Anything rather than shearing the heads off the bolts!<br /><br />I'll keep you up to date on my progress, and hopefully won't have to ask about getting broken studs out!<br /><br />Thanks again<br />Steve

 

[steviecops]

Re: Stuck lower unit bolts.

After letting the bolts soak for about a week, two of them now have some movement but the other two are still stuck.<br /><br />I've got a propane torch now, but really feel a bit nervous about using it. Could someone tell me the best technique to use please?<br /><br />Do I heat the bolts, the housing or both? Will the heat weaken the bolts and make them more prone to snap? How long should I apply the heat for? Is there anything that can go wrong and damage my engine?<br /><br />Sorry for all the questions. All advice will be gratefully accepted.<br /><br />Thanks<br />Steve

 

[rickdb1boat]

Re: Stuck lower unit bolts.

I would first heat up the bolt good and hot, then let it cool off naturally and try to remove it. That technique would be to try and break any corrosion loose in the threads. If that fails, heat around the bolt and see if it will come out. Heating around the bolt will expand the casing, but not the bolt, allowing the bolt to become "Looser" in the threads. You cannot over-heat it with a propane torch. Of course the paint may have problems....

 

[jim dozier]

Re: Stuck lower unit bolts.

Do what RB said except drink 2 beers first and put on some mood music to allay some of the anxiety with your first torching.

 

[steviecops]

Re: Stuck lower unit bolts.

Thanks for the advice guys <br /><br />I think the beers are a good idea <br />I'll let you know how I got on.<br /><br />Thanks again<br />Steve

 

[OBJ]

Re: Stuck lower unit bolts.

jimd......I like your style.

 

[steviecops]

Re: Stuck lower unit bolts.

Here's the situation.<br />One of the two bolts that had some movement came out pretty easily without the need for heat. The second one that had movement started to come out, then snapped <br /><br />The two bolts that were stuck fast are still stuck, although I have heated them up twice and cooled them down with penetrating oil. They have budged a little, but still don't want to come out and I'm frightened of snapping them. <br /><br />The bolt that came out had quite a bit of salt water corrosion around it.<br /><br />Now I'm wishing that I had taken the boat to the shop and had them fit the water pump kit! Should I give up and take the thing into the shop now, or keep trying? One snapped bolt is bad enough news, but I don't want to end up with 3 snapped bolts.<br /><br />Any more advice would be appreciated as I realy don't know what to do now.<br /><br />Thanks<br />Steve

 

[ledgefinder]

Re: Stuck lower unit bolts.

You're doing fine. The two that budge - get a good-fitting wrench on them and work them back and forth, increasing their range of swing a bit at a time. Keep doing the heat/cool & the penetrating oil. The aluminum of the casting expands a lot more, per degree of temp, than the steel of the bolt, so she will loosen up. <br /><br />What you're describing so far is pretty typical - dont' sweat it. Once you get the lower unit off, the broken-off bolt will still have a big part exposed, above the surface of the casting. You can hit it much more directly with the heat and the penetrating oil, then grab the end with some ViseGrips, and do the same thing - get it moving a bit, then work it back and forth, slowly increasing it's range of motion.<br /><br />When you put them back in, dip the threads in OMC gasket compound & they'll come out a lot easier for the next guy.

 

[steviecops]

Re: Stuck lower unit bolts.

Hey Ledgefinder, thanks a million for the advice and encouragement. It means a lot <br /><br />I have tried to work the two bolts back and forth, but they seem very tight in both directions. I'm a bit worried that the movement I can feel is the bolts twisting on themselves prior to snapping! I have heated them again and soaked in more oil, and they have budged just another fraction, but still very tight. I'll keep repeating the process as you suggest over the next few days.<br /><br />So far, I've only applied heat to the bolt heads. Should I now try heating the casing?

 

[jim dozier]

Re: Stuck lower unit bolts.

Congratulations Steviecop, by breaking off the bolt you have graduated and become a full fledged backyard "outboard mechanic". Seriously,<br />don't sweat this. As was mentioned above, if you snap the heads off, which is likely, there will be shafts sticking out when you pull off the lower unit. One of the problems with long stuck bolts is that it is difficult if not impossible to get penetrating oil down the shaft into the threads with the lower unit still on. Additionally, heating the head of the bolt probably doesn't heat the threads much, which is one reason to heat the aluminum with the propane torch (an advantage of propane is it won't get hot enough to melt the aluminum). After you break the heads off of the bolts and then remove the lower unit, you can continue to heat the shafts and the casting and put penetrating oil nearer the threads where it may do some good. The worst case scenario, which is not that bad, and happens not infrequently, is that you will at some point break the shaft more or less flush with the casting. Then you just file it flat, center punch it, drill it out with a new bit, and either clean the threads with a tap, or more likely install a helicoil thread kit which are easy to do and resists further frozen bolts. There is a light at the end of this tunnel and it isn't the train, its the sunny day you will enjoy in your repaired boat. Carry on.

 

[ledgefinder]

Re: Stuck lower unit bolts.

Yes, heat the casting (in fact, that's the part you want to expand, so have at it). I doubt you can hurt it with a propane torch. In fact, a propane torch is a little under-gunned for what you want to do, and you should be using it in a fairly determined manner (25 seconds per bolted connection, minimum). I use one of those small oxy-acetylene torches, and only use the propane torch if I've run out of oxygen. You have to be careful with the oxy-acet because aluminum will melt without warning, but I THINK it's virtually impossible to do with a straight propane torch. If I'm wrong, someone else please break in here.<br /><br />Let the heat/cool cycles do their thing. You want to pull on the wrench hard, but not so hard you start a fracture crack. It's a question of 'feel'. If you are getting any easy range of motion at all, you're all set - just keep working the heat/cool, penetrating oil, and work the wrench. Usually takes about 10-15 minutes per bolt. <br /><br />You may have already started cracking the two bolts. Don't stress if the bolts break off - just post back & we can talk you through that part. It happens frequently.

 

[ledgefinder]

Re: Stuck lower unit bolts.

JimD's dead on - or at least his experiences sound a lot like what I've encountered.

 

[steviecops]

Re: Stuck lower unit bolts.

Thanks again dudes If it wasn't for your good advice and re-assurance, I'd have given up by now. But here's the latest.<br /><br />The lower unit is off! O.K, I broke two bolts and got two out in one piece, but I'm really happy now that the lower unit is off and I can get at those studs. I have about half an inch on each stud to work with. I'll do as you say and apply more heat and oil, then I've got a nice big pair of Stilsons which I will use on them.<br /><br />By the look of it, the lower unit hadn't been off for a good few years. Everything gunked up with old oil. Cleaning it all up and servicing the water pump gives me a welcome break from the stress of broken bolts! <br /><br />Thanks again for all your excellent advice, I really appreciate it. I'll let you know when/if I get the broken studs out.<br /><br />Steve

 

[alanR1]

Re: Stuck lower unit bolts.

I rebuilt a 90hp johnson and had to do the propane torch deal for over 40 bolts on the water distibution plates, exhaust plate etc. It worked for every single bolt with heating the aluminum around the bolt sufficiently and working the ends with vice grips. If I can get out 40 or so you can get out 2. Good luck and be patient!!

 

[steviecops]

Re: Stuck lower unit bolts.

Thanks Alan. I would be pulling my hair out by the roots with 40 broken studs to get out!<br /><br />I'm going to spend a whole day tomorrow on the studs and rebuilding the water pump. By the way, couldn't get any OMC adhesive M today. Is there an alternative available from an auto parts shop?<br /><br />Thanks<br />Steve

 

[bollard]

Re: Stuck lower unit bolts.

My OMC dealer said that this is what Bombardier sent him for his order of Adhesive M:<br /><br />The product was 3M Scotch-Grip Rubber and Gasket Adhesive #847.<br /><br />Comes in a red tube and works just fine!