Broken bolt on port side thermostat

[82RAYSONCRAFT]

Have an 82 225hp Merc Black Max. Recently changed the water pump kit, poppet valve kit (due to no seat left) & proceeded to change the thermostats. Everything went fine on straboard side, but when it came to port side the top bolt became tight almost emediatly as they had never been replaced. Damn thing snapped off at the base of the threads! Drilled it with a center drill to make sure it was on center then proceeded to us reverse drill bit the easyout with no sucsses. (excus my spelling) After some frustrating time deccided to spray it and let it soak overnight. Got home today and put some heat on the threaded area with a torch and steel no go! My next attempted will be to drill out the stainless steel stud and to retapp the hole. I think this will be some what difficult knowing the stud is SS & the head is aluminum. Just affraid of not beeing to follow the threads in the alum head.<br /><br />Any Advise before I take the plunge?

 

[Rovernaut]

Re: Broken bolt on port side thermostat

I don't know if this will work for you, but i read of a fellow using heat and melting candle wax over the bolt threads, the molten candle wax seems to find it's way into the treads and lubricates it.(A bit like fluxing for soldering copper pipes )<br />Might be worth a try??????

 

[crookedmullet]

Re: Broken bolt on port side thermostat

Same thing happened to me on my 90hp Merc. Go to NAPA and get yourself the HeliCoil thread repair kit. I used the 1/4-20 size kit and it recommends the drill size to be 17/64(.2656). I had 2 bolt heads break on me. After some careful drilling to the depth you want it, use the tap that came with the kit and slowly tap the hole, make sure you use a light oil for lubrication. After you tapped the hole, use the inserts to get a snug fit in the hole. Once you installed the thermostat and poppet valve kit, place the cover back on. Now take a 1/4-20 bolt, screw a nut almost to the bolt head, make sure the bolt is long enough and then place a few washers finishing off with a lock washer. Take the bolt and screw it into the hole with the insert until tight. Now tighten the nut that was on the bolt onto the plate, making sure it's tight. Now get yourself a Dremmel and cut the bolt head off. You should be ready to go, you can use a little lock-tite if you'd like. Now make sure when you get the HeliCoil kit that it comes with stainless inserts. Hope the post is clear enough. Let me know how it goes.