Logo
FULL SITE MENU

Sheared bolt in lower unit - no access

M

mikeyc1985

New member
Hey all, hoping for some advice.

I was gifted a Concorde Chevalier by a friend.

Removing the lower unit from the yamaha 30hp and one of the four side bolts sheared leaving threads in top and bottom.

Initial thought was left hand drills and easy outs however, I don't seem to be able to get in due to the fin below.

There must only be 4 or 5 threads left in the lower unit!

Any suggestions on removal genuinely appreciated.

Many thanks

Mike
 
Image to support issue.
 

Attachments

  • download.jpeg
    download.jpeg
    44.4 KB · Views: 4
Any hidden bolt under the trim tab ?----The lower unit should now come off with that broken bolt not being an issue.-----Unless the driveshaft is stuck in the crankshaft.
 
Thanks for the reply :) That's what I hoped. The trim tab bolt sheered as well however, managed to drill that out. Looking at the bolt the threads seem to run into the lower unit, do they not? Thx
 

Attachments

  • download-2.jpeg
    download-2.jpeg
    49.6 KB · Views: 3
There is salt packed between the bolt and the housing. You will need to heat the housing around the bolt to expand the aluminum to release the salt grip. Use propane or MAPP gas torch to get the job done. Heat in circles around the stuck bolt. Do not directly heat the bolt stub. The goal is to expand the aluminum housing away from the bolt. Be patient and avoid beating on the housing or you'll break the cavitation plate. If it starts to move use wooden door shims and drive them with a hammer to help separate the housing and slide it off of the bolt. Things get hot so wear some BBQ gloves. This is standard practice down here in Florida for salt motors.
 
fitz73222 said:
There is salt packed between the bolt and the housing. You will need to heat the housing around the bolt to expand the aluminum to release the salt grip. Use propane or MAPP gas torch to get the job done. Heat in circles around the stuck bolt. Do not directly heat the bolt stub. The goal is to expand the aluminum housing away from the bolt. Be patient and avoid beating on the housing or you'll break the cavitation plate. If it starts to move use wooden door shims and drive them with a hammer to help separate the housing and slide it off of the bolt. Things get hot so wear some BBQ gloves. This is standard practice down here in Florida for salt motors.
Click to expand...
Thank you for the advice, very much appreciated. Will give it a go.
 
Which is why I asked the OP for the year and model identity. No one ever wants to disclose what motor they are asking questions about. As if all Yams are exactly the same.

1984 30 HP two stroke offered here in the USA through the 2002 30 HP two stroke all use a coupling nut to connect the shift shaft to the shift rod.

If the coupling nut is not removed the lower unit is not coming down. And if it does, there will be big troubles in the lower unit.
 
boscoe said:
Have you disconnected the shift shaft?
Click to expand...
Hi, yes disconnected the shift shaft (after a bit of a fight). So far I have had zero movement which is what led me to believe there may be threads in the lower unit and the sheared bolt holding it. Now confirmed that's not the case, seems its a case of heat and patience.
 
Worth saying, motor runs, shifts cleanly, however water flow seemed a little weak hence looking to service/ replace the impeller. I did however notice a lot of what appeared to be salt deposits coming out of the inlets as I was manouvering the unit so this could have been part of the issue. (Apologies for any surplus information and possible silly questions. This is my first boat and learning as I go).
 
mikeyc1985 said:
Hi, yes disconnected the shift shaft (after a bit of a fight). So far I have had zero movement which is what led me to believe there may be threads in the lower unit and the sheared bolt holding it. Now confirmed that's not the case, seems its a case of heat and patience.
Click to expand...
It will come apart, I once spent 14 hours trying to remove two gear cases on a pair of 2003 75hp Mercs from Naples, Florida. They had never been apart in 10 years in salt water. I had to pull both powerheads to get the driveshafts free so with heat and a dead blow hammer ,wiggling, wedges and timbers and a lot of heat they came apart, nothing bent, chipped or broken. It was my personal best and a test of knowledge and patience. We will get you through this...
 
Back
Top