Big Trouble for my 1987 175 TLCU

[trimmers]

So I got to the issue of my number 5 cylinder no sparky! I pulled the plug out and found a butt-load of melted aluminum all over it! Very dis-heartning. Figured I must of sucked a reed valve. So I tore off the head and found the piston completely covered in melted bits of aluminum. Surprisingly, there is no damage to the cylinder wall. Looking into the cylinder, the fuel air side ports are clean, but alittle debris made it out the exhause side. So I then ripped off the intake manifold keeping the 3 carbs on it so I could see the reed valves. Weird, but all valves are not only present, but they seem to be within specs and still serviceable. What gives? I took the little window cover off the side of the block on the intake side which exposes the side of the piston and the rings are there and appear to be just fine! So what did I suck into the cylinder? Could I have sucked something into the cylinder from the exhaust side? I cleaned off the head already and going to mask off and cover up cyl 1 and 3 and clean off the piston in question. I did a compression check on that cylinder before I tore it down, 3 weeks ago it was 90psi, now it is 76. Anyone know what could of done this?

 

[Gary H NC]

Re: Big Trouble for my 1987 175 TLCU

Check the rings on that cylinder.I have seen a piece of a ring melt into the top of the piston before.
Was a compression test done on that cylinder?

 

[trimmers]

Re: Big Trouble for my 1987 175 TLCU

Ya, I lost 16psi on that cylinder between yesterday and 3 weeks ago when I got the motor. I really think I have no choice except to tear the engine down and put new rings on it huh? I mean, it has to be the rings. What else could it be???

 

[jonesg]

Re: Big Trouble for my 1987 175 TLCU

Rings are cast iron, so where did the alum come from?

Are you running the correct plugs, Champions?
Did you rebuild the carbs?

We see quite a few posts like this here, guy gets a new to him engine and doesn't check it out before running it hard. All it takes is a bit of gunk in the carb.

watch this.
http://www.youtube.com/watch?v=SgavzDPDAy0

 

[trimmers]

Re: Big Trouble for my 1987 175 TLCU

I got new NGK's before I ran it. And honestly, I never got to run it for more than 30 seconds due to the check valve in my squeeze bulb failing. I did a compression check and the carbs were serviced by an evinrude shop before I took her home, the old plugs were ok looking (just some carbon). All cylinders were at 90 psi except the no.2 cyl was 86psi. The NGK's are like the champions in that they are the new style without the need to gap so it isnt piston to plug contact. Like I said, the reeds are in tact, and not warped or scarred or bent. The cylinder wall is smooth (very surprisingly). And like I said, what little bit of the side of the piston and rings that I can see, look great! I am new to outboards but very experienced with automotive engines (Built many V-8 Engines back in the 80's for circle track racing). This has me puzzled.

 

[Faztbullet]

Re: Big Trouble for my 1987 175 TLCU

Uh oh ...I can already see the posts claiming the NGK plug did it Usually when you see aluminum throw off from "eyebrow" with no scuffing in the exhaust/intake areas it a electrical problem,a bad coil,pack or bia's thru the timer base.

 

[trimmers]

Re: Big Trouble for my 1987 175 TLCU

Well, I did suspect a bad power pack due to a bad misfire both with the champions in it and then again with the new NGK's. I swapped coils around, but the fault stayed on the same cylinder. I did the ohms check of the stator and timer and all that in accordance with the seloc manual and it all passed so I got a new power pack, installed it, and thats when I dug deeper and found the metal crud on the spark plug. So can someone explain to me how something electrical or ignition related can effect a cylinder like this? I already priced a ring set and a retainer / needle bearing set and ready to redo my short block but I really want to know how this could of happened for future knowledge.

 

[trimmers]

Re: Big Trouble for my 1987 175 TLCU

Ok, so I tore it down and I found that one of the Seal Rings located on the lowest mount part of the rank was broke in half, but when i hold it together, it only sheered apart and nothing is actually missing. No other pieces or debris was located. I am still puzzled as to what melted all in the cylinder. Tomorrow, I will get the 11/32nd 12pt socket i need to remove the rod-cap and pull the piston to further inspect the rings. Looks like I am going to re ring the pistons, but new bearings in it and close her up!

 

[trimmers]

Re: Big Trouble for my 1987 175 TLCU

Wow, sorry for they typo's inlast post. Looks like I will spend 35 on new rings for the 6 pistons, 7 bux for the crank ring, 28 bux on a new lower crank bearing, and a mere 3 bux on the o-ring set! Not too bad. Basically, if anyone out thee can pass along any advice i might need in rebuilding this portion of the engine, i surely would love it. Last thing i wanna do is put it together only to take it back apart cause I messed up an otherwise easy task. Oh, and one more question... Can I replace the Rod bearings without replacing the rods? I know rods are matched set and MUST stay as a matched set, but is it ok to replace only the bearings?