AQ171c cogs on belt fell off

[AQ171C270SP]

Has anyone ever had an DOHC motor timimg belt fail? By fail I mean the cogs actually fell off the belt about 15 in a row. I am curious if this has ever happened to anybody and if they were able to just put a new belt on and everthing was alright.I was cruising at 3200 RPMs and the motor quit.I didnt hear any noise at all. I did try to crank the engine then realized my timing belt had lost cogs.I really dont want to take the head off if there is a chance my valves werent bent and there is no piston damage.My thought is if the damage was done what more damage could I do by putting on a new belt to see if I have good compression in all cylinders. I read this forum all the time and I will go with whatever seems to be the common answer.I do know from previous post that it is an interference motor,but is there a chance.I read in a manual that the pistons actually have a recess in them for valve clearance. Thanks to all who took the time to answer some of my questions on my last post.Hopefully Don will see this post and add his expertise and give his opinion on this. One more thing.... the belt didnt break, its not frayed in fact its very plyable.I dont understand what would cause the cogs to literally fall off as if somebody ran a razor knife on them.

 

[dwco5051]

Re: AQ171c cogs on belt fell off

Not an expert on this particular engine but from experience with other OHC units cogs do not just fall off. I sounds like something locked up and 15 or so cogs were torn off before things came to a compete stop. I would not replace the belt and try to run it until I found the reason for the belt failure.

 

[Don S]

Re: AQ171c cogs on belt fell off

First of all, it doesn't matter if someone else had this problem and got away with it or not. It all depends on what happened to YOUR engine.
Personally I would pull the head and look before I did anything. Something stopped turning, that is why 15 cogs were torn off the belt. Those piston indents if it has them is only enough to cover a partially open valve, not a open valve. If there was clearance, it wouldn't be an interference engine.

 

[AQ171C270SP]

Re: AQ171c cogs on belt fell off

Thank you for your input. I will be taking the head off for further inspection. As of now I have checked Tensioner pulley it seems to turn free with no binding.What else should I look at that could of caused premature failure of the belt. Is it possible that the belt was just a cheap aftermarket that is just disinergrating

 

[AQ171C270SP]

Re: AQ171c cogs on belt fell off. Problem found

Re: AQ171c cogs on belt fell off. Problem found

Well after messing with the boat I found the problem,at least the cause of premature timing belt failure.The seawater pump is seized up.I guess when it locked up, the motor was still trying to run and as the the cogs hit the gear they had no place to go but tear off.Time to finish tear down and see what kind of parts I need. Any advise on where to order pump,headset, valves, timing belt and who knows what else.I want to start lining up reliable parts source.Can I use automotive timing belt.Thanks Don for your input.This is a great site Seawater pump not seized, I was turning in wrong direction:redface:

 

[AQ171C270SP]

Re: AQ171c cogs on belt fell off

5051 Thank you for your input,I found the problem my seawater pump seized up.now time to get out the check book LOL. Have a good day. people like you make this a great site. Thanks well I thought it was seawater pump but its not I was rotating in wrong direction