Shearing starter bolts 2005 5.0

[cfeaster]

I’ve got a similar situation where I had a boat shop replace my starter (in 2005 5.0l Mercruiser) and I ran the boat a few times and when I took it out a couple of months ago, as always, the boat started right up and after a few passes in the river and a sharp turnaround, the boat stalled. Went to start the motor and the starter wouldn’t engage due to a broken starter bolt. What are the chances of it being something other than over or under torqued? The bolts had a little surface rust but nothing to write home about.

 

[Lou C]

Are you sure it was a broken bolt?
What can happen is this, there are a number of different aftermarket starters out there, they may all be slightly different dimensionally. The bolts must be the correct length for that starter. If they are even slightly too long the starter will not be clamped down to the block as it should be. Then the starter will shift under torque and that’s what breaks starter bolts. I installed a new ARCO starter and bought their bolts to avoid problems.
What can happen is that someone picks up a new starter uses the old bolts but doesn’t check to make sure they aren’t too long. That and they have to be adequately tightened (approx 30 ft lbs I think the spec from ARCO). If you want to have no problems next time make sure to use a matched set of bolts for the starter you install. If you want to check with the starter removed install & tighten one bolt. Measure the length from the flange on the bolt to the block. This distance should be less than the vertical height of the starter housing.

 

[southkogs]

I've started a new thread for you @cfeaster / Forum rules ask that you don't post to inactive threads over 90 days old, or hijack other peoples threads.

 

[Scott06]

I’ve got a similar situation where I had a boat shop replace my starter (in 2005 5.0l Mercruiser) and I ran the boat a few times and when I took it out a couple of months ago, as always, the boat started right up and after a few passes in the river and a sharp turnaround, the boat stalled. Went to start the motor and the starter wouldn’t engage due to a broken starter bolt. What are the chances of it being something other than over or under torqued? The bolts had a little surface rust but nothing to write home about.

Did you check to see if the engine was hydro locked? Take plugs out and look for water in cylinders

 

[Lou C]

As stated could be a hydrolock if you stopped fast
pull spark plugs crank engine over if water shoots out of plug holes that's it
Otherwise, starter bolts too long or not tightened enough.
If you do your own starter you have to make sure the bolts aren't too long, and also another thing make sure they actually thread in all the way before installing the starter, if there is rust or junk in the threads in the block they can seem tight but not be clamping the starter to the block tight enough. Same thing with installing cyl heads, intake manifold or even the bolts that hold the elbows to the manifolds, always thread in by hand, make sure they will go all the way in, if not you have to clean with a thread chaser, solvent and compressed air.