Mystery Part Appears in Engine Compartment

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Jun 2, 2004
3,650
Hunter 23.5 Fort Walton Yacht Club, Florida
Dude, That's the Cap to my Bong

I wondered where it went , man
 
Jun 6, 2004
21
Tayana 52 Ft.Pierce, Fl
The fact it's not threaded is not a problem. It could be held in place by a circlip. It may even be the retaining plug for a relief valve.
 

BobM

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Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
I think the yard threw it there so you'd have to ask them to check it out for $95/hr with a 2 hr minimum.

Bob
 
Oct 10, 2006
492
Oday 222 Mt. Pleasant, SC
Man are you lucky! You've got yourself a tuit. And I can't quite tell from the pictures, but it appears to be a round one.
 

higgs

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Aug 24, 2005
3,736
Nassau 34 Olcott, NY
The indents on the top could be for the clip that held it in place.
 

RAD

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Jun 3, 2004
2,330
Catalina 30 Bay Shore, N.Y.
Meanwhile the yard boys are following this post and laughing there asses off knowing full well that we'll never guess that its a bushing for a Singer sewing machine or grandmas vacuum cleaner :D
But I did think about it and this is a long shot but...... some sort of freeze out plug not belonging to this boat cause one of the yard boys had it in his top pocket and when he bent over.......you know the rest
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
It's a bellybutton plug- for people with a severe "innie".

Actually, it looks like an end cap to retain a free-floating shaft- like a cam shaft or rocker arm. There would be one on the other end of the shaft, so go back to the boat and look for that one, too.

(20 bucks says he does it, folks.)
 
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caguy

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Sep 22, 2006
4,004
Catalina, Luger C-27, Adventure 30 Marina del Rey
Try throwing it out, as soon as you do, you'll figure it out. Works for me every time.
 

Timo42

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Mar 26, 2007
1,042
Venture 22 Marina del Rey
From the looks of the oring, which has taken a set , wherever it was installed, it was there for quite a while, the second pic shows the outside, corrosion marks, and it was removed on purpose, see the plier and maybe screwdriver marks in the first picture. And yeah Frank, that always works:doh:
 
Jun 3, 2004
890
Hunter 34 Toronto, Ontario Canada
Here is my guess- i will buy into Higg's theory that it isnt used in a pressure application. How about on the suction side in the fuel system- specifically if you have a Racor filter. It seems to me there were some brass fittings on it- plugs for unsed inlets/outlets. Seems like it is meant for a permanent plug rather that a temp one tho>
 
Dec 2, 2003
392
Catalina 350 Seattle
Every time I looked at the picture I thought "Racor" - so I googled my way through a bunch of diagrams last night and wasn't able to see any cap-like / plug-like item that didn't have threads on it. Their "Water port probe cap" seemed similar, but has threads.

(I like these kind of topics - just don't let it drop off without some resolution....)
 
Aug 2, 2005
374
pearson ariel grand rapids
cap for a battery compartment on something?
looks about the right size for a double-A.
My little laser level has an aluminum cap which is pretty much identical, right to the O-ring, it's held in by friction of the O-ring.

Ken
 

higgs

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Aug 24, 2005
3,736
Nassau 34 Olcott, NY
C'mon rich, where are you at on this today. It is killing us.
 
Feb 10, 2004
4,235
Hunter 40.5 Warwick, RI
C'mon rich, where are you at on this today. It is killing us.
Well, I'm just sitting here reading all the different ideas you guys (and girls) are coming up with.

Actually I am 155 miles from my boat, but I will email my marina with a picture to show to the yard guys to see if they have any idea. I will definitely post their response.

I can say with good certainty that it isn't from a Raycor filter because I don't have one in the engine compartment (it's elsewhere), it isn't a cap from a grease fitting on the stuffing box 'cause the stuffing box is too far away and it also doesn't have a grease fitting.

Virtually everything on the engine is painted Volvo green and since this brass cap thing has no paint at all on it, it doesn't appear that it could have been a plug that was visible from the outside of the engine. And the engine has never been apart except for the raw water pump that has no such part on it.
 
Sep 25, 2008
2,288
C30 Event Horizon Port Aransas
One side of the plug is more tarnished than the other, suggesting one side is exposed to something the other is not, like atmosphere. Also having plier marks on it, would lead me think it is not from the inside of the engine.(not 100% on that but just a hunch)
The grease fitting sounds probably because of these things and it's not threaded suggesting that it didn't hold too much pressure which was mentioned before.
This is like the board game clue for boat owners, except no one got killed....yet!
 
Feb 10, 2004
4,235
Hunter 40.5 Warwick, RI
OMG, Mystery SOLVED!!!

I had no sooner clicked on "Submit Reply" on my above message than I realized what the part is.

However all of you are having so much fun with this, maybe I should just let you entertain yourselves with comments about "rountuit" and "bellybutton plug", and "dilithium crystals"! :laugh:

However many of you have really tried to help me and for this I am grateful. Now that I know what the part is and from where it came, I can tell you that some of your ideas were quite close.

For instance.....

GC8248 said "It may even be the retaining plug for a relief valve."

higgs said "The indents on the top could be for the clip that held it in place."

Ron20324 said "Maybe the dimples are for a retaining spring or such?"

SoSound said "Or the indentations could be there for an external retainer mechanism to help keep it in place"

But then higgs said "If this cap was meant to contain something that would be pressurized it would have threads." Sorry, nice try, but this was WRONG!

And Ron20324 said with regard to my chasing an end cap to retain a free-floating shaft - "(20 bucks says he does it, folks.) " Sorry Ron, you lost this bet.:cry:

OK, I won't keep you all in suspense any longer. Here is the skinny on this mystery part.....

It was in my engine compartment for the last eight years.

It was not part of my engine.

It came loose last summer when I had a mishap with my automatic Fireboy halon extinguisher. Here is what happened....

I had installed a high-output Balmar alternator, replacing my 60A standard unit. My Fireboy extinguisher's head was mounted about 12" above the alternator, but this Balmar alternator runs MUCH HOTTER than the standard one. In fact, it can run up to 250 degrees F. The Fireboy trips at 175 F.

Yup, you got it, I cooked my fire extinguisher and it went off. :eek: When it tripped, the heat sensitive RETAINING pin and a couple of curved clips collapsed releasing this round plug and the gas from the cylinder. I found all the parts last summer EXCEPT this round plug.

Since I really didn't know what pieces came loose, I didn't realize that there was a round plug that I never found. It probably lodged on top of the engine manifold and fell off during the launching of my boat last week.

See the attached sketch of the extinguisher head to see the part.

Thanks to all. I hope you enjoyed the puzzle.
 

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