1996 Mercruiser 3.0 Broken Starter Bolt

[Stevie13ray]

Not a professional so my terminology may be off. I've drilled out most of the old bolt that sheared off in the block. Pretty sure I messed up the threads. My question is, what size tap would I need to rethread the hole? Prefer one with a hex shank to go into a 90? drill attachment.

 

[alldodge]

Bolts are (3/8) .375-16 thread. get a 3/8 helicoil repair kit. The kit will contain the drill, tap and helicoil. Drill should be 25/64

 

[G_Hipster]

Tapping cast iron can be peculiar. I would not attempt to run the tap by a drill motor if that's the intention. It's a pretty good way to break the tap in the hole.

 

[Scott Danforth]

I would take the hour (or less) and pull the motor, put on the stand, flip upside down, remove the pan for clearance and then deal with the broken bolt

that way you can also find out why you broke the bolt in the first place.

 

[kenny nunez]

2xs on what Scott is telling you. The only other thing to check is that the bolts are not metric.

 

[Alumarine]

If you have the standard old style heavy starter you need a support bracket from the front of the starter to the block.
If so, it might be a good time to swap it out to the smaller style.

 

[Scott Danforth]

my guess is a hydro-lock event lead to the broken starter bolt