Thread: Cause of rod break, opinions?
09-06-2007, 09:12 PM #1
- Join Date
- Aug 2006
Cause of rod break, opinions?
I lost #3 rod in my 1390 last weekend, with horribly catastrophic results, ie: lots of broken parts. I really want to know what when wrong so I will list everything and if anyone has an opinion, please do tell.
Rod broken clean about 2/3 way up, top piece shows slight twist in grain of break, top piece bent a bit also, but grain still cleanly visible, hadn't hammered anything.
Piston wedged about midstroke, slightly turned off axis, pin brinnelled on rod bearings, but pin moves smooth in piston. lots of side clearance piston to rod, but washers still in place. Piston wedged because lower rod broke bottom of skirt, both sides. Bore clean, piston showing NO wear on original machining of skirts. Top of piston shows normal brown wash, no marks at all. Never touched head.
Head gasket perfect, no evidence of any kind of leakage, none.
Big end of rod bent a bit off axis(maybe because of how much stuff it hit) and a slight twist. Big end bearings look perfect, everything well oiled, no sign of water or lack of lube.
Crankcase looks like chainsaw went thru, broke bottom of cylinder both sides, tore up reed cage, rod lodged just thru cage into top cylinder.
Pieces of case all over boat.
Oil injection, all well, and extra ounce of oil per gallon, note no lube issues indicated.
Boat ran great until the big bang. 7380-7410 RPM if all out running, need to get prop tweaked again.(14/20 Dynafly Impros GK 1390 mod at present)
Only item of note: twice this summer when starting after a week of not running, cranked over hard at first, and fouled#3 plug with fuel. Began turning fuel off when not using, not more problem, suspect a leaky needle on #3, it is a good bit richer also.
Question: Can a carb leak enough fuel to hydrolock, and if so, can a starter motor be enough to bend a rod? If so, how can all that fuel get into the combustion chamber from that far down in the crankcase at cranking speed?
Thanks for any thoughts, just too big a loss to repeat!
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By cconigliaro in forum Kawasaki PWC Performance (2-stroke)Replies: 14Last Post: 11-18-2011, 10:11 AM
By MPower in forum Yamaha PWC Performance (4-stroke)Replies: 10Last Post: 03-03-2009, 10:55 PM
By boataddict in forum Sea Doo Open DiscussionReplies: 12Last Post: 07-04-2008, 12:58 PM
By SUPERBEAST in forum Sea Doo Open DiscussionReplies: 1Last Post: 05-09-2005, 05:53 AM
By spc9669 in forum 4-Tec PerformanceReplies: 4Last Post: 05-08-2005, 11:30 AM