Logo
FULL SITE MENU

Stripped thermostat thread

B

butty99

New member
Hi everyone , has anybody come across a stripped Yamaha thermostat thread? M6mm x1.0 ???? I go to torque the bolt and it goes slack ??
Investigated a bit further on the net, and it seems common to repair with a helicoil ?? Has anybody got a another way?
Has anybody bought a kit of ebay ? Any advice on this subject will much appreciated .....
Thanks
 
Good and snug is the proper torque value on all small aluminum threads. Take the bolt up to your local hardware store and properly ID the thread and pitch the get the proper helicoil kit. Never use a torque wrench on small bolts on a outboard engine period. Install new gaskets with a light coat of permatex aviation on both sides of the gasket.
 
Thanks for the quick reply that's good to know?
its a 6mm thread and 1.0 pitch bolt , checked on a thread gauge ?
Stupid question but can I drill into the stripped hole on the actual outboard or take the the cylinder and cooling jacket off first then do it ? Because I'm thinking if I drill when it's on the outboard, the metal strips of the drill and tap will go into Casing or water jacket ?? I don't know what's behind ???
thanks
 
Are you speaking of the thermostat cover? If my assumption is correct, the service manual indicates the 2-stage thermostat cover tightening torque is first, 2.9 ft-lb on all 4 screws, then final of 5.8 ft-lb.

If Yamaha "never" intended the thermostat cover screws to be tightened to a specific torque, they would not have included this torque setting in their service manuals.
 
Dip the drill in a can of bearing grease to catch the shavings then do the same with the tap. Go two full threads and back out wipe the grease off and dip it again until the threads are cut.
 
Great idea mate on the grease ? This is why we use the forum?
thanks everyone for your advice I'll try it all this week ??
 
You can use the grease trick for installing a helicoil for spark plug holes without pulling the head. Old mercs did not have a head you had to pull the pistons out to remove the shavings.
 
image.jpegGot all my gear ready to do the helicoil and I thought two questions :
1. Do I put the helicoil at the bottom of the thread hole ( bolt thread is 40 mm long) or top , because if you look at the pic , the bolt binds the two parts together the cylinder head and thermostat housing ??
2. You've gave me great advice on the grease on the drill and bit ? Have you got another trick for removing the piece that snaps off when you have inserted the helicoil to its depth, to allow for the bolt to srcrew all the way thru it ??
thanks again !!
 
Take a punch or a bolt that fits just inside the threads and push in the tab should break off. I wouldnt worry if it falls in the water jacket if the hole goes all the way through. Unless you can snap it with needle nose pliers?
 
Thanks mate , sounds the way !!
Any of your knowledge on the first question on the helicoil depth ? Just below hole or bottom to pull the sections together ?
 
You want the coil one half thread past flush with the surface then snap off the tab. Your gonna want to remove the water jacket cover to get the helicoil at the correct depth in the head. Your putting in a new thermostat may as well get the new cover gasket and put it back together correct. Have you done a compression test? It never hurts to install a new head gasket while your there.
 
Have done a Compression test around 110 ? 22 yr old motor is this acceptable ? Yeh will do head gasket , but dreading extracting the bolts out of the block, i've heard they snap quite easy any tips ???
 
Back
Top