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Broken bolt in lower gearcase

B

Bart Hanline

Member
I'm in the process of replacing the impeller on my 1960 40hp Evinrude Lark II outboard and in the process of removing the bolts connecting the water pump to the lower case I broke one of them off. This is after trying the loosen the bolt with Liquid Wrench, and heat. The Seloc manual said that breaking bolts while removing water pumps is pretty common. Anyway, I tried using vise grips to grab onto the nub and this worked for one of the bolts, but the other bolt broke a second time. I was able to get a pilot hole started in the bolt but then my bolt extractor broke of in the hole. I tried drilling the broken extractor out but it just chewed up the drill bit. Now I'm in a pickle. Short of taking the entire gearcase to a machine shop, I'm not sure what else to try. I thought of coming in from the bottom up, but because of the shape of the gearcase I can't get a drill started in the hole plum. Whattttya think? Drop back and punt?

Thanks in advance!
Bart
 
Do you have a mig welder? If yes, get a hand full of nuts the same size as the broken bolt and weld one to what is left of the bolt. Then try to unscrew it. You will probably break the weld before you get it out. No problem, just weld another one on and try again. The trick is that after you tear off enough of them the broken bolt will start to loosen from all the heat you are applying during welding.

If this does not work for you, weld on one more nut, Get a group 27 or 31 battery, a heavy set of jumper cables and a stick weld rod (make sure the rod is thinner than the bolt you are removing). Hook the cables to the battery, hook the other end of the negative cable to the housing, put the weld rod in other end of the positive cable and hold it on the welded on nut until the rod starts to smoke a little and remove the rod and loosen. This will heat the whole bolt.
 
Just by way of an update... I tried everything that I could to get the broken bolt out of the lower gearcase to the point I started to damage the lower gearcase. I decided it was time to find a machine shop, so I made a few calls to companies out of the Yellow pages. I found a place in Charlotte called Production Tool and Die and ended up talking to the owner. He said that he could help, but that I probably wouldn't want to pay machine shop prices. He asked me to bring the part in and he would hook me up with one of the machinest who would be willing to do the work on the side. They ended up using an EMD machine to melt the bolt with electricity. The machinest had to make an electrode and a plug for where the drive shaft enters to lower gearcase. He said it took about 2 hours for the EMD to do its magic. The bolt was melted out and kept the threads intact. It ended up costing me $50, but I think that was a bargain especially since I was out of options. I got the new impeller installed and the water pump back on without a hitch.

Thanks for your advice above, I might have been able to avoid the whole situations with a little more patience and the chemicals. Oh well, it is all a learning process for me right now.
 
Actually the process is ---EDM---------- Stands for-------- Electro Discharge Machining------------I used to work in a shop that has one of the largest facilities for this process in North America.--------A competent operator can use it to " drill / machine " a hole 0.004" in diameter.
 
Aluminum, when heated, has a much higher expansion rate than steel...use a propane torch to thoroughly heat the area and wait patiently for the heat to be absorbed...at that point, apply only slight force to the wrench and the bolt will almost always come loose. Broken bolts usually result from insufficient heating and the application of excessive force.
 
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