Mystery Fragment

[itstippy]

I've got a 1961 Johnson 18HP FD15 broken down to the major components, am getting things clean and assessing what I'm dealing with. I bought the motor for parts and have never seen it run. It is (was) filthy. But it has 95 lbs compression top and bottom and I'd like to bring it back to life. At some point a lucky operator must have found one of those underwater structures where fish congregate; however, he apparently found it at full throttle. The motor came with two lower units, both in a box. But I digress.<br />While getting the gunk out of the exhaust housing (tower) with a bottle brush a little fragment came out. It is obviously broken off something larger. It's 3/4" long, 1/4" wide, and 1/16" thick. Kinda half-moon shaped. Shiny black on one side and rough on the other, possibly flaked off. It certainly looks metalic, but does not attract to a magnet. No flex at all; hard and brittle. I can't find anything it looks like it came from. If it's from inside the powerhead I guess I've got the parts motor I originally purchased, but I don't see any likely components in the parts catalog exploded view. What IS this thing? Where is it from? <br />

 

[Todd Humphreys]

Re: Mystery Fragment

Looks like end piece of the reed valve.

 

[rabidfish]

Re: Mystery Fragment

Ditto, but i would take it to a local dealer to help identify it.

 

[itstippy]

Re: Mystery Fragment

I don't see any "reed valves" in the parts catalog view. This motor has two daisy-shaped leaf plates with star-shaped leaf stops. I assume the leafs are spring steel. I'll pull the intake manifold and leaf plate assembly off to have a look, though. Can't hurt, might help.<br />This mystery fragment is not steel; a magnet has no affect on it. Whatever it is it was in the exhaust housing (leg, tower). I doubt it could have passed through the combustion chamber, if it could fit through the ports, without getting pulverized.

 

[Harker]

Re: Mystery Fragment

It's not the impeller key is it?

 

[lark2004]

Re: Mystery Fragment

difficult to believe that it would be key, they are made of steel. This is apparently not magnetic.<br /><br />Does the edge look like it snapped off something?

 

[itstippy]

Re: Mystery Fragment

It definately broke off something larger and got lodged in the leg. Water pump housing? No, too shiny and black as can be. Drive shaft seal? Maybe, but not from any of the type I've seen. Did the original seals had some kind of hard Bakelite type material in them? The diameter of the curved edge suggests something that fit in the driveshaft seal hole. Something from inside the exhaust baffle? I can get 12 of the 13 screws loose but not the last one - tried an impact driver etc. Hesitant to raise too much heck with it, and anyway the parts diagram shows just gaskets and a steel inner cover in there.

 

[papasage]

Re: Mystery Fragment

could be a pice of piston the part from top ring to top of piston . some of the older motors the top ring was close to the top and with no led gass they would break off . that is why the older pistons like 1974&75 70 hp i have arenot avaible anymore . the newer ones will fit with a wrist oin converson. i would pull the headand have a look . papasage

 

[itstippy]

Re: Mystery Fragment

Thanks guys. I will pull the intake and the head when I address the powerhead and see what I can see. I'll also have another go at that stubborn last screw on the exhaust cover.

 

[itstippy]

Re: Mystery Fragment

Finally got a day off work so I pulled the head and exhaust cover off. Intake leafs look good - really good. Exhaust chamber was caked with carbon big time. Things got plenty hot in there with all the carbon build up on the wall next to the cooling channel. Not hot enough to turn carbon into diamonds (phooey, no diamonds) but hot enough to do strange things to the exhaust chamber gaskets. Between bathing in unburnt fuel during warmup and cooking after warmup they turned into a hard, brittle, metalic-like substance that breaks off shiny black on the surface next to the stainless inner cover. Mystery fragment identified.<br />Pistons look OK I guess. Some scoring on the upper. I'll clean out the carbon, button it back up, and do a decarb as soon as I get it running. Glad I got that exhaust cover off - the carbon was really something. Is that common in a 44 year old motor?

 

[rabidfish]

Re: Mystery Fragment

It's common in a 5 year old motor that never got de-carbed.

 

[itstippy]

Re: Mystery Fragment

I don't wanna fight with those exhaust cover bolts ever again. What do you pros use on them during reassembly? Anti-seize? How about the head bolts? I used sealer on the bolts when I put a seal kit in a lower unit last year per the manual, obviosly helps prevent water corrosion and galvanic action. But they aren't subject to heat.

 

[rwise]

Re: Mystery Fragment

I have used a nickle based anti-seize compound before with good results. pricey though, but, I aint no pro.

 

[Scaaty]

Re: Mystery Fragment

Originally posted by papasage:<br />piece of piston papasage

Yep...run a file across it...get SHINY? Its aluminum and a piece of the piston ring lands