help with 150 johnson

[kray274]

model number J150STLCRD serial number J6001470
I was on the lake yesterday running to a fishing hole, the motor was at WOT at about 5700 rpm, it then lost power and died. It did not want to start up at first but when it did start it was knocking like crazy, almost sounded like an ether knock. I shut it back off as quick as I could. I sat there for awhile and took the cowling off looking for a hole in the block or something, no hole. I started it back up fired off instantly, no knock of any kind. Now it will not get above 2500 rpms, so I babied it back to the ramp and got it loaded up. I pulled the plugs out and the top plug on the drivers side bank was covered in oil, the bottom plug on the passenger side looks to be melted, it has some kind of material all on the electrode and insulator.
Can someone give me some idea of what I might be looking at. Oh yeah I used a bright led light to look at the bottom cylinder and could see a fresh scratch on the piston.

[Ranger482V]

Never blown a motor, but that doesn't sound good! Wish I could help.

[DoferGofer]

It is time to pull the heads and take a peek inside.



Regards,

[ChampioNman]

At least pull a compression test.

[Lockjaw]

If you got a melted looking plug, chances are you have a piston problem. Sorry.

[kray274]

I have been doing a little research on the net and from what I understand the cylinder that had the messed up plug may have been running lean. I took a closer look at the spark plug and it's not melted but does have some kind of deposit on it. I bought the correct plugs for the motor thanks to the chart on this site and I am going to to do a compression check this week comming up. I have to work this whole weekend. I am hoping and praying that no piston damage occured. If this is caused by a lean condition what causes that? Any and all advice and help is greatly appreciated. Thank you.

[TopJimmy]

I am definitly not one of the experts but just 2 weeks ago I bit the bullet and rebuilt all 6 of my carbs rejetted all 6 of them and have had a ton of problems go away now I only have 4 tons of probs left to go..
.

[kray274]

Well, I did a compression test today. Not good news. The bottom cylinder on passenger side would not build any pressure. All other cylinders held 100#'s. I guess I will be tearing into the motor, to see what needs to be done. I figure while it's down I'll rebuild the carbs also. I am sure I will have lots of questions for the experts on here. I will happily listen to any advice that ya'll have.

[fishnfool38]

Sorry too say this but you are going to have more than a carb rebuild if there is no compression on that cylinder good luck! The upside is these boys can walk you thru it!

[kray274]

I pulled the head off the motor today and this is what awaited me. What causes this? [IMG][/IMG]
I am going to have the motor rebuilt but I would like some advice on the cause and how i can keep it from happening again.

[ccuboy123]

burnt piston!..... ouch.. well biggest thing is to see if the cylnders are in good shape. hopefully a hone job and new piston and rings on each

[kray274]

I finally got around to getting a ball park figure on getting my engine fixed, 1500-2500.00 depending on what all the guy had to do once he tore it all down. I actually thought about doing it myself since I have rebuilt a couple of car engines before, so I went and got a shop manual. It was almost like reading a foriegn language. Anyway let the saving begin and hopefully I can get it in the shop about Febuary. Can anyone give me some idea about could have caused that cylinder to burn like it did? Thank you, Keith.

[ChampioNman]

I'd check the high speed jets on the carbs and see if they were pluged up or if one had backed out causing a lean condition.

[SEAHORSE]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ChampioNman &raquo;</TD></TR><TR><TD CLASS="quote">I'd check the high speed jets on the carbs and see if they were pluged up or if one had backed out causing a lean condition. </TD></TR></TABLE>


Arent' you going to blame the VRO pump ?

[ChampioNman]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SEAHORSE &raquo;</TD></TR><TR><TD CLASS="quote">


Arent' you going to blame the VRO pump ?</TD></TR></TABLE>

I was saving that for last.

[Wind Talker]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ChampioNman &raquo;</TD></TR><TR><TD CLASS="quote">

I was saving that for last. </TD></TR></TABLE>

[kray274]

No VRO.

[Lockjaw]

That's why it broke.