Spark plug full of metal....

[Duxbass]

Here's the details.<br />1988 Johnson GT175<br /><br />started, headed out after warming up. Hole shot was great, planed out, ran good, then lost RPM and speed. I shut it down. trolled back to the ram. Flywheel turns. engine is not locked up. <br /><br />Now, standing behind the motor looking forward to the front of the boat.<br /><br />Right top cylinder- ok<br />Right middle cylinder- ok<br />Right bottom cyl- Moisture<br /><br />Left bottom cyl- Moisture<br />Left middle cyl- Moisture<br />Left top cyl- Packed with Metal?<br /><br />Head gasket?<br />Reeds?<br /><br />Any ideas? What failed? What all do I need to do.....?

 

[Dhadley]

Re: Spark plug full of metal....

You say its locked up but the flywheel turns. If it's locked up the flywheel won't turn. But at this point the next step is to pull the heads.

 

[Texasmark]

Re: Spark plug full of metal....

Two senario's I personally experienced.<br /><br />1. Salt water ate through the cylinder walls and water entered the combustion chamber on one engine.<br /><br />2. Another engine, thermostat slowly developed a stuck closed problem which made the engine act funny but I couldn't pinpoint the problem till one day it finally finished sticking closed while I was at WOT and it (the engine) locked up. Absolutely amazing how fast a boat will stop when the engine siezes.<br /><br />I let it cool and got it restarted to nurse it home but at home investigation revealed metal on the plug. Pulling the exhaust water jacket cover off confirmed the problem..aluminum particles all over the rings and sides of the pistons...$1000 rebuild later and no thermostat, no problems.<br /><br />HTH<br /><br />Mark

 

[Duxbass]

Re: Spark plug full of metal....

I pulled the head.... upper left cylinder which is the one with the packed metal in the spark plug. <br /><br />The upper left piston looks like crappy cast aluminum....... The inside of the head looks ok. the clinder wall looks ok from what I can see........

 

[Texasmark]

Re: Spark plug full of metal....

Got me on this one. All the suggestions I would have are voided by the evidence you provided....no connecting links....like head looking like piston, or scratches (scoring) on the cyl walls.<br /><br />Sorry,<br /><br />Mark