Stripped Threads on Engine rail

[dwb2620]

Hey guys,

Is there a way to repair a stripped thread on an Engine rail? It is a 4-40 thread size on a 1/4 inch wide engine rail. Any ideas would be welcome.

Thanks,

David

 

[PondSkimmer]

Not sure why you have a threaded rail but what about a "T" nut or blind nut?

also could try to re-thread with a 6/32 if they are metal.

 

[dwb2620]

Just for clarification, this is on a 20 Eagle SG rigger. Any ideas?

 

[Myron_Sleeva]

Presume you are talking about the motor mount rail in the boat?

Simplest repair is to turn it into a stud. Screw in the appropriate length 4-40 bolt from underneath and then use a nut to hold the engine down.

 

[mercguy]

Myron's suggestion of making it a stud is a good idea providing there are good threads all the way thru the mount. I like to install a Heli_Coil for stripped threads. The kit gets a little expensive but it is a good thing to have in your arsenal. Some auto repair places have heli-coil kits but usually are for bigger sizes. McMaster-Carr has all the sizes you need.

Mercguy

 

[bzubee]

heli-coils do work very well and a 4-40 size is very common in our application.

 

[tnrcboatracer]

I have the 4-40 helicoil set. Another option is to redrill and retap to 5-40. I personally use 5-40 bolts on my 20 boats for greater strength.

 

[Dr Hydro]

Myron's suggestion of making it a stud is a good idea providing there are good threads all the way thru the mount. Mercguy

If you use a bolt, you don't need any threads to hold the bolt. The head of the bolt keeps it from falling out.

 

[mercguy]

Dr Hydro

You are quite correct that you don't need threads but it is difficult to hold either the nut or the head of the screw (depending which way you install the screw) from turning while you tighten the other end, especially in a 20 rigger with the motor in place.

Mercguy

 

[Preston_Hall]

Either use a helicoil or drill it out to a larger screw like 5-40 or more common 6-32.

 

[Mark Anderson]

I heli coil 4-40 all the time. To me using a none standard size like a 5-40 is a pain. The simplest thing woud be call CMDI and get a new rail. How about shifting the motor back a 1/4 inch and redilling?

 

[tnrcboatracer]

5-40 is a standard size, though not available at the LHS. I buy screws by the 100pc box at very reasonable prices. 6-32 is an option if it fits through the engine lug holes, or you can drill the lugs slightly larger to fit.

 

[Don Ferrette]

Just get a new set of rails, they are not really thick enough on the 20SG to support a 6-32 & I doubt you'd want to punch the case mounting holes that big even if you could. I wouldn't mess with moving the motor either, that'll change the fit of everything- the cowl opening, linkages, shaft length etc. etc. :blink: