1981 70hp, stuck bolt in lower end...help?

[NJ lakes]

I recently purchased a decent running 70hp, model J70ELCIM. Since the previous owner could not vouch for the age of the water pump impeller, I decided it would a really good idea to change this. Unfortunately the 5/8" bolt in the center rear of the housing was not going to budge, and I decided this may be better put off until the end of the season in case this results in a stripped bolt hole or broken bolt. Does anyone have any suggestions to get this bolt loosened up? It seems that there are some open holes where the bolt goes through the lower housing and into the upper housing, that maybe I can get enough penetrating oil in there for a period of time to loosen it up. Can anybody confirm this would be the case? What about heat? I figured there's enough aluminum that it would probably dissipate before doing any good, and could warp the casting.
If anyone had been through this and knows what (or what not) to do I would appreciate any words of wisdom.
-John

 

[dog5233]

Re: 1981 70hp, stuck bolt in lower end...help?

I was in the same situation with my 1990 Evinrude 48SPL this past spring. Five bolts on the housing, the aft bolt, the one on the centerline , 7/16"dia, 3 1/2 in. long, was frozen. Long story short, I broke it trying to get it off. That started me on a three week journey of extracting the broken bolt stub, and drilling/retapping/installing a helicoil. All ended happily but only after much frustration and many sleepless nights. On my motor, the threads were inches removed from the bolt head. No way to get PB Blaster on the threaded hole until the lower unit came off after I broke the bolt. Even then, I could only get penetrating oil in above it for gravity seepage by squirting it through the hole I had painstakingly drilled through the stub, to attempt using an easyout bolt extractor. I tried heat, vibration, everything, multiple times. nothing budged it. Your best shot is heat (propane not MAPP) directly on the outside of the housing where the threads are. Some suggest trying an impact wrench. Or giving the head a sharp blow with a punch to break the surface tension. Didn't work for me. When I finally gave up and ground out the stub with a Dremel tool, I found that the oil had not penetrated the threads a bit despite bathing for days.
One way or another you need to get that bolt off. My impeller and impeller plate were in terrible shape, I'm sure due to the fact that the previous owner was stumped by the frozen bolt and put the job off as a result.

 

[mikesea]

Re: 1981 70hp, stuck bolt in lower end...help?

If you have access to an air hammer with a blunt end as close to head diameter as possible,adjust hammer so it produces a good strong vibration.This often loosens them up.Or as suggested with the torch,however ,and with respect.I choose to use Mapp gas because it ges hotter and thus slows cooling time,Heat and vibration are your friend here./I know its hard to get the heat to that area,but patience and moving from side to side top to bottom will allow enough heat to eventually heatthe alum housing.When the job is done.! grease the bolts.2 change the impeller once a yr.This insures not only cooling but stuck bolts .Especially in salt water and for engines that lay up for long periods

 

[fireman57]

Re: 1981 70hp, stuck bolt in lower end...help?

Start soaking it now and every chance you get until the end of the season and maybe you won't have to go through all that. good luck.

 

[tx1961whaler]

Re: 1981 70hp, stuck bolt in lower end...help?

IF you do break the bolt off, please don't try to use an EZ-Out extractor. It is guaranteed to break off in the bolt, making a bad situation worse. I use left-handed twist cobalt drill bits, starting pretty small and working out larger, using plenty of oil while drilling (drill is in reverse, of course). Usually when I get close to the size of the bolt with the drill bit size, it just backs out the thin shell of what's left of the bolt.

 

[fireman57]

Re: 1981 70hp, stuck bolt in lower end...help?

tx1961 is right. I can't tell you how many easyouts have had to be drilled and they are harder than the bolt. Instead of using oil on your bit use honey. It does not burn and cools better. Also stays where you are drilling. An old machinist told me this years ago and it works like a charm.

 

[jonesg]

Re: 1981 70hp, stuck bolt in lower end...help?

machinists remove seized studs from blocks by touching the stud with an arc welder for a second, clamp other terminal to the skeg anywhere.
The corrosion is resistance , the welder turns that corrosion into ash, you can often unscrew the stuck bolt by hand after this.
google the technique, its used by many engine machine shops.

...forget ez'snapoffs.

Also,
Try tightening the bolt, use an impact driver, elec ones work if you allow time for them to bang away. I also find penetrating oil usually doesn't penetrate for beans.

 

[NJ lakes]

Re: 1981 70hp, stuck bolt in lower end...help?

Thanks to everyone for the suggestions. The air hammer (zip gun) is one of my favorite tools, so giving a few shots with that to loosen things up should be a piece of cake. I agree about the so-called "easy outs". Having done quite a bit of work in machine shops and working on cars I know how well they don't work. I had always heard about the arc welder trick, but never connected why. I do have an arc welder here and I know how to use it so that will be on my list of things. Geez, with all those tips I'll hopefully get this thing out without inflicting much damage.

Any more ideas, keep 'em coming.
-John

 

[NJ lakes]

Re: 1981 70hp, stuck bolt in lower end...help?

BTW, one trick I can pass on regarding drilling out rusted bolts: I recently had to drill out a wheel lock that had the head stripped on a VW Golf. Cobalt drills wouldn't touch this thing. I found that a cross-cut rotary file (high speed steel) on a die grinder ate through quite nicely, but you have to be careful to control the direction it's going as it doesn't have the stability of a drill bit. On the bolts normally found on boat motors one of these should make quick work if nothing else can do the job.