Yamaha 4hp outboard snapped upper casing bolt question

[Jason]

hi Everyone,

I am better with oars and sails than with outboards.  Haven't had the best of luck with them.   In working on my Yamaha 4hp outboard a snapped a bolt that holds the upper casing to the lower crankcase.   Any motor experts out there that can answer how big of a deal this is?   There are many other bolts holding the upper casing to the lower crankcase.  I dont think the upper casing holds any lubricant, I think that this bolts hold the powerhead to the casing.  Can anyone shed some light on this.  Disassembling the whole thing and backing out the bolt would be a big project.   The bolt is snapped off way up the hole, and due to the hole's closeness to the casing, is cannot be reached with even a small drill.   Thanks for any constructive input!



Jason

[MacGyver]

in my opinion it is, others will have a differing opinion of course.
I think it is due to the idea that the bolts hold it together in a even fashion. This would distribute any forces evenly amongst the bolts.

If it was me, I would probably dissassemble it and try to fix it, then if it didnt work on my own, probably reassemble and run till I got another engine, the money to have a mechanic to the extraction, or just until it smoked itself off due to undue stress.

But I am pretty handy with engines (except Carl's engines..... for some reason, his eluded my abilities) and feel very confident with mechanical things easily.

Mac

[mikew]

Jason, I have a Yamaha 2001 4 cycle 4 hp ob, but have not taken these bolts out. Some block bolt holes are only threaded a short distance and stop into a blocked hole . Others may be threaded all the way through so water or oil or if a 2 stroke, crankcase gas/ oil mixture could seep through the open hole. If there is a gasket where the broken bolt is, then the question is to see what does the gasket seal?  What harm would result if the gasket leaks in that area?

Mike

[moonlight]

The question that pops to mind first is, if you were even messing with that bolt, WHY?  It looks like a powerhead base gasket, and yes, it's likely to leak, in this case, four stroke oil.  But maybe not, I'm not looking directly at the motor.  But what is #6 in Boats.net picture?
But I have to assume (with all the requisite troubles of making an a$$ of u and me) that messing with that bolt had a purpose; and if in releasing it broke, huh, well, continue.  If in reassembly, yep, crap-ola, gotta take it apart again.
But if as alleged, there's no real reason to be here in the first place (conspiracy theories will abound), run it and see what happens.  At worst, it'll leak.  I doubt it's the sort of thing that would burn the whole motor though.