65HP Main Bearing Bolt Engine Threads Broke

[05220713]

Please bear with me on this. I have a 1973 Triumph 65HP 3 cylinder that today I started up in hopes of going out fishing tomorrow. Motor stared right up, great. But after it ran for a while I was looking over the motor and noticed the threads that hold one of the main bearing bolts on the port side of the motor between the top and center cylinder broke apart around the bolt.

Motor still starts right up and runs great but how long can this last? Will I do major damage to the engine without fixing this? How can I fix this as the part that broke appears to be a casted part of the block.

Is my motor doomed?

 

[boobie]

Re: 65HP Main Bearing Bolt Engine Threads Broke

Can you post a pic of it ??

 

[05220713]

Re: 65HP Main Bearing Bolt Engine Threads Broke

I will try tomorrow. Not sure what the hold up is tonight but I cannot get the pictures to upload. Thanks for your prompt offer to help.

 

[05220713]

Re: 65HP Main Bearing Bolt Engine Threads Broke

Boobie, I have pictures but I am still unable to get them uploaded to attach to this post. Not sure why as I have posted other pictures without any issues in the past. Anyway after further research the part that broke is the thread casting, for lack of a better word, on the intake manifold for the middle cylinder at the 4:00 position on the port side. Besides the two studs that the carburetor attaches two it appears that there a 6 other bolt positions on the intake manifold for each cylinder and the one I mentioned above cracked off and the bolt fell out.

Not sure if this will work but here is a link to the an eBay part that may help to pinpoint the area I am speaking about. I am sure this should be fixed but will it do much harm to continue to run until I can get it fixed?

Johnson Evinrude Outboard 0385140 Manifold Intake 385140 317304 | eBay

 

[jbjennings]

Re: 65HP Main Bearing Bolt Engine Threads Broke

THe worst that could happen would probably be an air leak if the seal breaks. If it does, it will probably lean out that cylinder and possibly ruin that cylinder and piston. I've never had one suddenly break like that for no apparent reason, but cast aluminum is kind of brittle and a weak casting could have caused it. Is there a way to put a bolt on there and use a washer and locknut to hold that case together, or is it a dead end thread hole? Was this motor recently repaired and possibly had an over-torque on the bolt due to dirty or dry threads?