115 HP JEY BOAT 4TH PISTON BURNING OUT

[STULEE]

I have a 1996 115 hp jet boat. I am having problems w/ the 4th piston burning out as soon as the warning horn goes off the piston head is damaged and the sparg plug is coated.. The same gentleman has worked on my boat. Some potential problems discussed are:<br /><br />fourth piston running to lean because of water, air, or fuel.

 

[clanton]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

How is the timing being set? What kind of fuel pump, what size fuel line, what is engine temp? Water deflectors every changed? Carb float settings?<br />Thimig check for each cylinder at full throttle 5000 rpms?

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

THE GENTLMAN MENTIONED THAT THE TIMING IS TO SPECS. I ALSO BELIEVE THE FUEL PUMP WAS REPLACED W/ THE SAME KIND. WE BOUGHT THE BOAT ABOUT 1 YEAR AGO. WE HAD PROBLEMS GETTING IT STARTED. TOOK IT IN AND THE 1ST GUY RECOMMENDED RE DOING THE CARBS. EVER SINCE THE 4TH PISTON KEEPS BURNING OUT. CAN YOU ELABORATE ON THE WATER?

 

[Dhadley]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

THE GENTLMAN MENTIONED THAT THE TIMING IS TO SPECS.

And what spec did he use? At what rpm did he set it?<br /><br />What spark plugs are you using (be specific)?

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

TIMING=25 DEG, SET BACK 2 TO 3 DEG<br />REP PUMP W/ OMS REP<br />FUEL LINE SIZE 3/8<br />WATER DEFLECTORS CHECKED<br />TIMING CHECKED 1ST AND THRD CYL, 5000 RPMS<br />SPARK PLUGS L82C, CHAMPIONS

 

[Dhadley]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

Good info. What does the piston look like?<br /><br />Is the top edge burned away by the exhaust port? The center of the piston dome burned? The dome OK but the sides scuffed?

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

THE SIDE OF THE CYL IS SCUFFED. THE PISTON HEAD IS REALLY BURNT AND THE PLUG HAS A COATING ON IT.

 

[Dhadley]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

I take it that the sharp edges on the dome are burning off as well as the top edge next to the exhaust port.

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

I AM A ROOKIE. I DO NOT FOLLOW YOUR QUESTION. THE IS SCUFFING ON THE CYL, PRIMARILY IN ONE SPOT. THE WHOLE TOP OF THE PISTON HEAD IS FRIED. THE SIDES OF THE PISTON ARE IN DECENT SHAPE. HOPE THIS HELPS.

 

[Dhadley]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

OK. That sounds like an ignition problem. It could be related to a lean condition but the sides would, most likely, show the most damage. <br /><br />Is this the first piston to burn or has it done it more than once?

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

THE ONLY PISTON TO BURN IS #4. #4 HAS BURNED ON NUMEROUS OCCASIONS. COULD IT BE A PROBLEM W/ THE CARB?

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

HOW DOES THE IGNITION DIFFER FROM THE TIMING?

 

[Dhadley]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

Since its hurt number 4 piston several times we can be assured that the cause of the problem is being transfered from rebuild to rebuild. Replacing the hurt piston is fixing the effect -- not the cause.<br /><br />If the motor still runs, now would be a good time for your tech to figure out whats causing the damage to the piston. It has to be changed anyway but troubleshooting now wont hurt the piston. You dont want to risk damaging another new piston.<br /><br />He needs to look for any type ignition problem like double firing, cross firing, flywheel center magnet loose, etc. Obviously going thru the carbs is a must also.

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

UNFORTUNATLEY THE MOTOR HAS BEEN DISSASEMBLED. ONCE IT IS PUT BACK TOGETHER WHAT CAN BE DONE TO PREVENT BURING THE PISTON? IF EVERYTHING TOU MENTIONED CHKS OUT WHAT CAN BE DONE AFTER THE REBUILD TO CHK THE FOURTH PISTON?

 

[Dhadley]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

The only thing thats going to prevent another piston issue is to find and correct the cause. Unfortunately the motor will have to be running to do that. <br /><br />This is the most important part of any rebuild -- finding out the cause of the piston damage. Obviously it should have been done the first time. <br /><br />What brand pistons are you using?

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

THIS GENTLEMAN HAS TRIED TO FIX MY BOAT ON 3 DIFFERENT OCCASSIONS. JUST LAST NIGHT THE 4TH PISTON HEAD BURNT OUT FOR THE 3RD TIME. I PAYED $1,350.00 FOR WORK TO BE DONE. HE HAS HAD THE BLOCK ZYGLOED (SP) AND THE 4TH HEAD HONED 3 TIMES. HE HAS HAD THE BOAT FOR 9 MONTHS. WHAT IS MY RECOURSE. OBVIOUSLY HE IS TRYING TO FIX THE EFFECT AND NOT IDENTIFYING THE CAUSE. IT IS MY BELIEF THAT SINCE THE WORK IS GAURANTEED. I SHOULD BE DUE A REFUND.

 

[KentBoyle]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

Sorry to hear about your problems. I have the same engine/jet in my boat and am curious as to where the water deflector is? What does it do, and is it easy to get to?

 

[Solittle]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

From your description I would look for a lean condition caused by crud in the carb that feeds #4.<br /><br />I also think it is time to stop throwing good money after bad & find a new wrench. I doubt that you have any recourse but you might try small claims court if necessary.

 

[seahorse5]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

Ask your mechanic to "index the flywheel" and check each cylinder's timing with a timing lite at high speed. Perhaps an ignition pack is "double firing" causing very advanced spark to #4 ignition, resulting in pre-ignition damage. A bad ground connection can cause the pack to fail. This is assuming that there are no air leaks in the crankcase and the carb has the correct float level, jets, and is clean.

 

[STULEE]

Re: 115 HP JEY BOAT 4TH PISTON BURNING OUT

IF THE WORK IS GARAUNTEED, AND HE IS YET TO FIX MY BOAT. SHOULDN'T I HAVE RECOURSE. HAS ANYONE RAN INTO A SIMILAR PROBLEM?