Wondering if part of carb could be in intake manifold or engine on a 4.3 Mercruiser

lgnott

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Jul 22, 2018
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Hi Everyone,

I've lurked around for awhile, but this is my first post. I did some searching on here to try and come up with an answer, but I think this may be a bit of a unique situation.

The casting on the carburetor that "bridges" up to receive the stud that holds the air cleaner in place broke free of the carburetor. For the life of me, I don't know how this happened (I'm quite particular about the condition of our boat), but it's where we are now.

When I set the piece back in place to see how it broke, the port and starboard pieces fit together properly, so I know I'm not missing any pieces there. Unfortunately, it looks like I am missing a small chunk between the bow (forward) side of the carb and the "bridge." I'm guessing that piece (or pieces depending on how it broke) fell down into the carburetor as it would really have nowhere else to go.

I estimate that this boat has about 5+ hours of run time since this broke, but just became aware of the fact that a piece has been missing. I haven't started it since I discovered this, but it seems to be running as well as ever.

I removed the carburetor today and used an endoscope (camera) to try and look into the intake manifold searching for the piece(s), but it was very difficult to see. While trying to do my inspection, I noted that the passages between the top of the manifold to the head seem to be pretty short and very straightforward with not many places for something to get stuck. Am I wrong?

With 5 hours of run time, is there any point in disassembling more to continue to look for this? It would seem to me that piece is probably long gone and probably passed right through with the exhaust. Obviously there is always a risk of engine damage with something like this, but how likely is it based on the possible size of the piece?

1989 Rinker 186 Captiva, 4.3l V6, Thunderbolt IV - searched high and low for the serial number on the engine but couldn't find it stamped or tagged on the engine. The motor is original to the boat.

Thanks for all the help.
 

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Scott Danforth

Grumpy Vintage Moderator still playing with boats
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that piece is now mashed into the top of one of the pistons.
 

lgnott

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Jul 22, 2018
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Does this imply I shouldn’t worry about it or that I should be gearing up to tear the motor apart?
 

Scott Danforth

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I wouldnt worry about it. not a thing you can do
 

lgnott

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Any long term damage risks? If not, I'll get it all put back together and get back on the water!
 

Lou C

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Scott is most likely right, if you are really curious you can remove all the spark plugs and scope the cyls and see what's there. If it runs well and does not make unusual noises or start burning oil I would leave it be, unless your inspection reveals it is bouncing around in one of the cyls, in that case it would be worth taking it apart to get it out. BTW, looks like from the pic someone overtightened the nut holding on the flame arrestor. They don't need to be all that tight, just snug! That might be what cracked off that small piece of cast aluminum.
 

lgnott

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Jul 22, 2018
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Ok, perhaps I'll pull the spark plugs and do one more inspection before I button it back up.

That's interesting, I hadn't thought about that bolt being too tight as the cause. I had wondered if somebody leaned on the engine cover while retrieving something from the hatch. I'll keep that in mind when I service it going forward. I had somebody else winterize it last year, but I'll be doing it this year.

Thanks for the input everyone!
 

Alumarine

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It also looks like the outer diameter of the flange has a few chunks broken off as well.
Does the top of the doghouse hit the flame arrestor?
 

Bondo

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Any long term damage risks? If not, I'll get it all put back together and get back on the water!

Ayuh,..... Welcome Aboard,..... The answer to that question won't be known, til the other end of that long term,.....
 

lgnott

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Jul 22, 2018
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Thanks everyone, I really appreciate it. The rest of the carb looks to be intact. I'll be re-assembling this weekend and hopefully be back on the water as well.

Safe boating!
 
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