Head bolts keep backing out.

[Mathnap]

I have a 1964 Evinrude lightwin 3 HP outboard, just replaced the head gasket and the head bolts keep coming loose and causing the motor to stall and then not re-start. I torqued them to 80 inch lbs start the motor and it will run good for about 5 minutes then stall, I re-torque them and it starts right up, any solutions to this problem?? Maybe loctite, maybe lock washers????

 

[F_R]

Re: Head bolts keep backing out.

Something is terribly wrong with this picture. You are telling us they come loose enough to stall after only 5 minutes? That almost seems impossible. You should be using gasket sealer on the threads, if anything. But I don't see how you could do anything wrong enough to cause that kind of results.

 

[boobie]

Re: Head bolts keep backing out.

I think you have other problems rather than the head bolts. Spark ?? Fuel ?? Have you checked those ??

 

[Mathnap]

Re: Head bolts keep backing out.

I think you have other problems rather than the head bolts. Spark ?? Fuel ?? Have you checked those ??

I have good fuel and good spark, new fuel and good fuel flow rebuilt carb., new spark plugs gapped at .030. Motor runs great but head bolts keep coming loosen once I tighten them back up motor runs great, weird isn't it. i think I might drill a small hole in the head bolts and run a wire between them. Any other thoughts?

 

[boobie]

Re: Head bolts keep backing out.

Are they the original bolts ??

 

[Mathnap]

Re: Head bolts keep backing out.

As far as I know they are the original bolts, I just bought the motor a few days ago.

 

[racerone]

Re: Head bolts keep backing out.

Something is wrong here !!----Is waterpump working properly ??

 

[Mathnap]

Re: Head bolts keep backing out.

Yes, waterpump is working fine.

 

[Bosunsmate]

Re: Head bolts keep backing out.

I have a 1964 Evinrude lightwin 3 HP outboard, just replaced the head gasket and the head bolts keep coming loose and causing the motor to stall and then not re-start. I torqued them to 80 inch lbs start the motor and it will run good for about 5 minutes then stall, I re-torque them and it starts right up, any solutions to this problem?? Maybe loctite, maybe lock washers????

Did it do this beforehand?
Why did you replace the headgasket to begin with?
Is 80 inch pounds right?
Thats only 6foot pounds

 

[Mathnap]

Re: Head bolts keep backing out.

Yes, it did it the day after I bought it. Me and my son took it out to a quarry to test out how it was gonna run for us. Started right up on the first pull, ran for about 20 mins. then stalled and never started again that day. Took it home and started investigating, found I had no compression in the top cylinder and 30 lbs. in the bottom one, checked the head bolts and they were loose and the gasket didn't look so good so I replaced the gasket. Head bolts will viberate out, but the motor runs real smooth until the bolts get so loose I have no compression, tighten them back up and it runs fine. crazy ****.

 

[Bosunsmate]

Re: Head bolts keep backing out.

Yeah crazy and annoying
Have you tried lockwashers?

 

[Mathnap]

Re: Head bolts keep backing out.

i just drilled a small hole in the head of each bolt and after I torque than down I'm gonna run a small wire between them and see what happens, should work.

 

[boobie]

Re: Head bolts keep backing out.

Let us know what happens. My only guess would be somebody changed the bolts at one time and they are to long to hold the head down properly.

 

[F_R]

Re: Head bolts keep backing out.

After 24 years of being a pro outboard mechanic, and literally thousands of motors, I can honestly say I have NEVER seen head bolts vibrate loose on any motor. The reason should be interesting if you ever discover it.

 

[Mathnap]

Re: Head bolts keep backing out.

My belief is that someone through the years changed the bolt threads to 1/4-20 course thread and they should be 1/4-28 fine threads, after using high temp RTV in the bolt holes and wiring the bolts in place I'm gonna fire it up today when the rain stops and see what happens, if that doesn't work I'm gonna helicoil the threads to 1/4-28 and use loctite as a last resort.

 

[racerone]

Re: Head bolts keep backing out.

Nonsense ---They were always 1/4-20 NC threads.--------Fine threads are simply not used in aluminum for this application !!!-----------I believe someone overtightened the bolts and the aluminum threads are ready to strip out.------------Put 1/4 helicoils in all 6 and you will have no more problems.----Since 1968 or so I have never seen bolts do what you are describing , so something is wrong here.----I have a number of these older 3 hp motors and no such thing as 1/4-28 threads in them for head bolts !!

 

[Mathnap]

Re: Head bolts keep backing out.

All six holes have 1/4-20 helicoils in them now

 

[racerone]

Re: Head bolts keep backing out.

Are the helicoils flush with tho edge of the block or are they properly installed below the deck ??---Makes a huge difference here !-------One small helicoil / hole or 2 of them ???????------Perhaps the helicoils are just way too short !---Someone has made some drastic mistakes in the repair / maintenance of this motor.-------As other folks have said and I agree 110 % that they have never seen this issue in years and years of shop experience !!!!------Any pictures of the motor.

 

[racerone]

Re: Head bolts keep backing out.

Addition info added to post #18-----Perhaps you are just pulling the helicoil against the cylinder head and not compressing the gasket !!

 

[boobie]

Re: Head bolts keep backing out.

Just for the heck of it, measure the bolt length and then the depth of the holes head included.