HELP 1994 Johnson 200 venum bad piston???? pictures

[johnsonl]

I was on the lake Saturday night fishing, I was able to get the boat on plane went about 100 yards and heard what souded like a belt hitting the cowling. I quickly shut the motor down. I than re-started moter in nuetral for 2 seconds, still had noise, shut it down and trolles 4 miles back to the ramp. Brought boat back home and checked spark, Fine, Than I checked compression . All were 91-93 except top port side, it was 56. I pulled the head and saw that the top of the piston was in bad shape. I could see what looked like small metal peices of the oil ring. Scared the top of piston and bottom of the head. What could have caused this? I have the vro disconnected and pre mix at 50:1. Only about 150 hours on engine, well maintained and serviced regularly. I know that I will have to replace the piston but will the head have to be replaced? I will include pics later tonight. The cylinder walls were not scared or damaged at all, infact they still had the factory cross hatching on all three cylinders. I have rebuilt automotive engines before, and I have a Seloc book for this motor. What are some of the things that I should look for and how much should this cost? I also would like suggestions as to where to buy the piston, rings ect. Any ideas would greatly help. I woul like to have all materials on hand befor I tear into block. Thanks and wish me luck. Good boating, Lee.

 

[johnsonl]

Re: HELP 1994 Johnson 200 venum bad piston???? pictures

ttt

 

[mikesea]

Re: HELP 1994 Johnson 200 venum bad piston???? pictures

The engine needs to be rebuilt.You can dissassemble it and after a good exam.if the other 5 cylinders are clean ,the pistons can be put back in there original cylinders.be sure to mark them.You will need to replace the broke one.You MIGHT be able to get away with a honing of the cyl.I would prefer going to next oversize and put a new piston kit (piston, ,rings and wrist pin).If you want to GAMBLE,you can hone the cyl,while the engine is intact,and sneak a piston of std.bore back in.You can get at the rodbolts fron the intake side by removing the carbs and intake.You then HOPE all trash is out and the other cylinders didnt pick up any through the ports.Ive seen it done sucessfully more often then not,BUT the gamble could mean blowing worse next time.As for why.My bet is a dirty carb that didnt get the fuel and OIL to the cyl.or the timing may some how caused too much advance.I know some mechanics were retarding to reduce detonation possibility.The spark stop should have a rubber bumper,if its missing that can cause more advance.You definatly want to go through your carbs,for a good cleaning.If it were my motor.and was a clean eng.I would do a total rebuild ,6 new piston kits next size over.But at very least ,I would tear apart,insuring all ports and passages are clean of debri frow blown cyl.A total rebuild is costly,about 125 a piston kit ,then machine work.As for labor,if you can do a break job,you can do an outboard.Torque specs are important,your dealing with alum.As for cyl head.If the sealing surface is bad,(it shouldnt unless corrosion)resurface or get another used.We usually grind any high spots from the broken rings down to dimples and be sure to remove any steel from the rings that may have become jammed into alum.You likely can reuse
sue

 

[johnsonl]

Re: HELP 1994 Johnson 200 venum bad piston???? pictures

thanks, Mikesea. I will finish the breakdown tomorrow and post pics.

 

[don wenger]

Re: HELP 1994 Johnson 200 venum bad piston???? pictures

Lee,I am sorry to hear about motor,if I had know some thing like that was going to happen I would not have sold it to you,but you still got a dran good boat,good luck ====Don