Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

Checkmate - guess I should have figured that out, bad suggestion. Thanks for the sanity check!

Rush - Thanks for the advice. The mechanic is going to check the exhaust flappers and then go at the engine with a mechanic's stethoscope if it isn't in the exhaust.

WetteVette - Thanks for the reply. I hope you're wrong too for my wallet's sake. Pier57 tuned the motors after they replaced the springs, and they ran great for the other 12.9 hours since purchase, so hopefully it wasn't detonation. But you're right, I didn't think it sounded good either.

All - I just remembered that there was a small amount of water coming out of the "hinges" around the Captain's Call flappers in the thru transom exhaust when I ran the starboard motor after it cooled off (with the exhaust routed through the prop). Could this be a sign of an exhaust problem in the Y pipe???

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

If the knock is noticeable at idle you may pull one plug wire at a time and see if if lessens. Theory being that the knock will reduce when spark is removed if it is just one rod.

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

the small water leak is not uncommon at all and not really a sign of any kinda problems inside.

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

This is correct,
If it is a rod knocking the sound will be lower and may disappear when the plug wire is removed. I would recommend getting a stethoscope and listening to the engine in various locations to pinpoint the sounds location.

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

Thanks for the help BadDog, Hillbilly and Nobody.

This is why OSO is such a great board!!!

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

Did you do lifters when you did the plugs?

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

I still want to know why the plug flew out? was it loose? Did it take any threads with it? Detonation can bend a rod and kill the bearings but as Rush stated after a spring job I would suspect a rocker first. Generally speaking if you have a bearing knock it is out of rhythm and inconsistent but gets worse with engine load. A rocker will be constant and it will be loudest on the valve cover. The exhaust flapper I don't have any experience with.

Roby

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

Roby,

Sounds like the ceramic portion of the plug only came out.

1stfntn,

It is also possible that you are hearing noise from the out-drive. Remember that the drive shaft and U-joint are always turning.

Loose rocker arm seems likely given that you just had springs changed.

Good luck

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

When they replaced the valve springs, did they have to take off the exhaust manifolds? An exhaust leak makes a ticking noise. I always check the simple stuff first.

Re: HP500 Carbs - blown plug and problem in bottom end at 171 hours?
 

The only way to do this with the head installed is to use compressed air running through the spark plug hole via a disconnected compression gauge hose. Then the springs are removed using a specialty spring compressor. The exhaust manifolds as well as an intake can stay intact.

Roby