2004 Merc 2 stroke 90HP seized after rebuild

[steven.swiatek]

Hey yall. So my 2004 mercury ran perfect until one day sucked all of the oil down in a short trip and seized up on the way home (oil alarm didn't work). Cylinders 1 and 3 were scored so I opted to have bored .30 over and rebuild. I also opted to bypass the oil injection (capped off the pump lines) and went with premix for the break in. 2 hours into the break in I held steady at 4krpms for 3 or 4 minutes and all of the sudden lost power. I thought it was ste stator so I used my trolling motor to get home. Replaced the stator and still nothing, so I opted to pull the exhaust and have a look after I did a compression test and got almost nothing out of cylinder 1. Turns out cylinder 1 destroyed itself again. Other two look fine, but in 1 the rings welded themselves to the piston on one side which scored up both sides of the cylinder and piston near the intake and exhaust ports... before I just opt to do a full rebuild again, does anyone have any idea why this would have happened? Thanks for any and all advice.

-steve

 

[racerone]

Up to you to do the inspection.-----Water pump and carburetors.------Find the cause or you will ne rebuilding it again and again.

 

[steven.swiatek]

Up to you to do the inspection.-----Water pump and carburetors.------Find the cause or you will ne rebuilding it again and again.

I already ordered a new water pump kit.. But my temp gauge was reading normal temps. Could that still be the issue? And what with the carb could cause such a quick catastrophic issue? I am asking because I honestly dont even know where to start.

 

[racerone]

Well----If a carburetor is restricted / blocked it reduces the amount of fuel ( cooling from that fuel ) going in one cylinder.----Also reduces amount of oil.-----Check the oil recirculation hose and fittings as well.-----Motors need a new water pump impeller about every 5 years too.

 

[ThomW]

If you are mixing the gas and oil now and the carb feeding the #1 cylinder isn't allowing enough mix through...she's going to get hot quick....not enough oil to keep things going smoothly.

 

[steven.swiatek]

If you are mixing the gas and oil now and the carb feeding the #1 cylinder isn't allowing enough mix through...she's going to get hot quick....not enough oil to keep things going smoothly.

Would it be a safe bet to just restore the oil injection system?

 

[Scott Danforth]

it would be a better bet to go thru the fuel system. you most likely ran lean on cylinder #1

 

[ThomW]

Would it be a safe bet to just restore the oil injection system?

I don't think that removing it was the issue. I had a 2001 merc 200 that I removed and ran 50:1 through for years. The issue is more likely that a jet in the carb was clogged, or the adjustments were off, or they weren't sync'd correctly and the #1 cylinder wasn't getting enough gas/oil to it. Like Scott suggested...go through the fuel system...clean the carbs...adjust them...and lync and sync them...

 

[Alumarine]

What ratio were you running for break in?

 

[steven.swiatek]

What ratio were you running for break in?

50:1

 

[Scott Danforth]

50:1

Should be 24:1 for breakin

 

[steven.swiatek]

Here are some pics

 

[racerone]

Typical damage.-----Lack of oil ??-----Were these pistons " dry of oil " when you took them out ?-----Did you do the work yourself ?-----What piston to bore clearance was used ?-----What elevation are you running at ?

 

[steven.swiatek]

Typical damage.-----Lack of oil ??-----Were these pistons " dry of oil " when you took them out ?-----Did you do the work yourself ?-----What piston to bore clearance was used ?-----What elevation are you running at ?

I had it machined at a reputable shop, but I reassembled it. I am in NE Florida. The pistons and cylinders felt like there was still some lubrication.

 

[racerone]

Did they bore the cylinder out by an actual 0.030" ?----What size did they bore it to ?----What was the piston to bore clearance??----Did you check it ?----If yes , where did you measure it ?----Top near the rings ?----Middle of the piston ?---Just above the skirt of the piston ?

 

[steven.swiatek]

Did they bore the cylinder out by an actual 0.030" ?----What size did they bore it to ?----What was the piston to bore clearance??----Did you check it ?----If yes , where did you measure it ?----Top near the rings ?----Middle of the piston ?---Just above the skirt of the piston ?

I did not check the clearance. The guy bored it to 0.31 over, which is what the merc manual says. I did not check the piston to bore clearance, but I know he did after honing. Do you think this looks like it wasn't bored to the right clearance?

 

[Faztbullet]

Not lack of oil or clearance....my bet is honing debris from block not cleaned properly. The damage is at intake and exhaust port and can clearly see something enter cylinder at transfer port on piston..whats the cylinder roof look like?

 

[steven.swiatek]

Not lack of oil or clearance....my bet is honing debris from block not cleaned properly. The damage is at intake and exhaust port and can clearly see something enter cylinder at transfer port on piston..whats the cylinder roof look like?

You mean where the spark plugs are? It looks fine. No damage or anything. Would the debris come in from the exhaust side? Or just the intake?

 

[Scott Danforth]

did you thoroughly clean the block after getting it from the machine shop? or just get it and start assembling?

Normally it takes about 25 minutes of washing going into each and every passage with pressurized water, dawn dish soap and a variety of scrub brushes and pipe cleaners.

 

[steven.swiatek]

did you thoroughly clean the block after getting it from the machine shop? or just get it and start assembling?

Normally it takes about 25 minutes of washing going into each and every passage with pressurized water, dawn dish soap and a variety of scrub brushes and pipe cleaners.

I did clean it with a pressure washer and some dawn, but I would not say impossible that there was something stuck up in there. And just for more situational awareness, I ran it according to the break in instructions for about two hours before this finally happened. It wasn't until the end of the trip when I was running about 4k rpms for 3 or 4 minutes that I lost power and realized something had happened.