73 80hp merc swollowed a bolt

[wishinIwasFishin]

G'day mate's <br /><br />been away fishin for a week out at lake kepit ( Northern N.S.W australia) the first two day were great no probs.Then comein back to camp one morring crusin at about 32 mile/hour (just off WOT) and it all happened the motor gave a surge and then a horrifying rattle and that when I pulled back on the throtle and she stalled(was within sight of camp) got it going with the use of warm up lever an snuck back to camp on three plugs<br /><br />The compresstion test showed that <br />No. 1=152 psi<br />No. 2=150 psi<br />No. 3=52 psi<br />No. 4=155 psi<br /><br />so pulled it down (with help of mech. [he did most])to reveal that one of the bolts that holds the reeds onto the crank had snaped off at the head and gone in to the firing chamber resulting in stuffed piston/rings<br /><br />the bore looks remarkably unmarked(nothing a hone woun't fix)<br /><br />My question is is the conrod likely to be bent and are there going to be more of these bolts brake and what would cause this one to brake.Would it be as some one surgessed harrmonic vibration and how to avoid this<br />and can I get away with a new piston/ring and start again

 

[alcan]

Re: 73 80hp merc swollowed a bolt

Hi Wishiin<br /> This isn't a comman occurance. Why the bolt broke is anybodies guess. I would replace all of them though.(both blocks). I think it probably got loose and was sheared off. Check the con rod for straight. If it's good, use it. If the rest of the engine is still in tolerance then just slap a new piston and rings in her and go. Of course if measurable wear is found you might consider other options.

 

[wishinIwasFishin]

Re: 73 80hp merc swollowed a bolt

thanks alcan <br /><br />this motor has never been apart as it still had the seal on it from mercury and is in very good shape as the wear in the rings (end gap )is within tolerance

 

[wishinIwasFishin]

Re: 73 80hp merc swollowed a bolt

g'day mate,s<br /><br />any body got any Idears on what would or could cause the bolt to brake? <br />Was it somethin I did (like drive it wrong)<br /><br />cheers daryl