knock

[the dog house]

I was running at 3800 rpms in my 2520 with a 2001 0x66 250 hp i had been running for about 5 minutes when the rpms stated to drop there was no noise ,then the motor died...i tried to restart and it sounded like the motor was siezed...would not crank over...waited about 2 minutes after checking battery conections hit the key again and the motor fired right of,
now it has a loud metalic knock sound..it wasnt smoking ..i drove it back to the dock ,about 1.5 miles..the engine seemed to being running smooth but it had a knocking sound.... it had plenty of oil in the tank..I guess what i am asking is has anyone else had a problem like this and is it some kind of inherant faliure with this engine...seems i read somthing similer on this sight but i was unable to find it..Also the engine only has about 250 hrs...I feel it is a connecting rod but i guess i am hoping it is somthing simple...LOL..

 

[jcmcclellan]

It probably seized. The two minutes you took checking connections allowed the piston to cool and shrink a bit, breaking it free of the cylinder wall. Thats why it was able to spin over and start after a couple of minutes.

 

[the dog house]

Thats what i am thinking also I have been a machanic my whole life ..But i guess i am just in denial..

 

[MaxOut]

It sounds like the piston cracked where the wrist pin goes through it. The piston is softer than the pin and is likely to have cracked making the hole oblonged. I would not run this engine until you investigate further. Check your oil system to ensure it was working properly. Remove spark plugs and put a wrench on the flywheel move back and forth to see if you hear any play or clunk. You may only be looking at a new piston if you are lucky. Probably need to hone the piston walls to remove carbon build up to help prevent it from happening again. Good luck I hope we are wrong.

 

[DaleH]

Agree, knocks and even faint ticking is using wrist pin related. I tell you, ANY 2-stroke motor should be decarb'd every 50-hours or so.

 

[MaxOut]

Agree, knocks and even faint ticking is using wrist pin related. I tell you, ANY 2-stroke motor should be decarb'd every 50-hours or so.

YUP! Good advise and sad to see with such low hours.... I have over 350hrs. on my 2007 (4-stroke though):shock: .

 

[the dog house]

Well i finally ran a compression test ,i had 150 psi in 5 out of 6.
the bad one was the lower cyl port side it only had 25 psi..
removed the head and intake,found rings had siezed on piston ...I only had to hone the cyl very little to get rid of scratches..so all and all a pretty cheap fix..1 piston and rings and a few gaskets and bearings..
all the other cyl seem fine..

 

[Catfish]

The Dog House

Hey brother, you better determine the "Root Cause" of your problem or you better keep your tools out. Maybe the water intake clogged for a short time, the water pumps weak, or its a oil problem. Your engine only has 250 hours on it. They are known to be tough long lasting engines that will run hard all day. What went wrong to cause this? I too have been a mechanic all my life. Id hate to see it happen to you all over again.

Good Luck
Catfish

 

[John_Madison CT]

Sorry to read about your Ox66 problems. They are rare, but it does happen. Had you ever done a decarb and did you always use Ring-Free??

I have the same engine with about 330 hours.

Thanks,

John

 

[the dog house]

I think that is my problem there was a lot of carbon build up on the rings..I purchased the boat in april of 08..i dont know if the old owner used ring free or decarbed the motor..I did check the other cylinders and they had a fair amount of build up..When the problem happend ,after i got it started again i checked the water flow and it was strong.so i dont feel that was the problem.I also checked to see if a reed got stuck open,there was no problems therei did also notice a build up of carbon on the head side of the exhaust port..???? on all cylinders not just the one that failed...
I feel if the oil system was the problem the other cylinders would have failed also..maybe i am wrong?