knocking sound like Detonation wont pull over 4krpm 96 200EFI Merc

[kell490]

Went out to the lake yesterday and the motor ran fine all day then at the end of the day I was running with the motor down in heavy chop about 30mph when it lost power then just stalled. After restarting it I was unable to get it back on plane would not turn more then 4000rpm. I also notice knocking sounding like detonation not insync with the motor, so I don't think its a rod or anything. It took 2hrs at 10mph to get us back to the ramp as long as I kept it about 1800rpm it didn't knock only a few times a minute. I plan on taking it in, but any ideas what it could be?

 

[achris]

Re: knocking sound like Detonation wont pull over 4krpm 96 200EFI Merc

Kell490,<br /><br />Welcome to iBoats.<br /><br />Unfortunately is sounds like you've done some real damage here. Start by pulling the spark plugs out. Make sure you know where each plug came from. Look at the firing ends of each of them. You should see black and a bit of oil. You may find that one of them has aluminium on it. If it has this is really bad. That aluminium should be on the piston crown! <br /><br />Get back to us with the results of checking the plugs.<br /><br />Chris.............

 

[WillyBWright]

Re: knocking sound like Detonation wont pull over 4krpm 96 200EFI Merc

I always hated getting Detention back in High School. (Sorry, couldn't resist)

 

[kell490]

Re: knocking sound like Detonation wont pull over 4krpm 96 200EFI Merc

I dropped it off at the dealer they said they would tell me whats wrong for $80.00, so Its worth that instead of guessing. It's probably my fault for letting the motor sit for a year at a time without use or winterizing. Although we don't have winters here in AZ. Probably going to cost me 3k for a rebuilt powerhead.

 

[kell490]

Re: knocking sound like Detonation wont pull over 4krpm 96 200EFI Merc

Got the bad news from the dealer. They said one cylender is at 60psi the rest are 120 or so. They told me I will need a complete rebuild for $3400.00. I asked about the remanufactured powerheads they told me they do not recomemend those. They did say 3400 would be the max it could be less if they don't need to replace some things. Is there any chance I could rebuild this myself. I have rebuilt car engines and a couple of dirtbikes. I have the service manual.