2 newbie questions

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blackstang932005

Seaman
Joined
Apr 1, 2008
Messages
50
1986 omc cobra 4.3. There is whats looks like a vacumm line port on the backside of the carb. I couldnt find were it would go so i just plugged it. Anybody know what im talking about. I just purchased a oem manuel. But this is driving me nuts. My other question is my RPM guage reads at 1000 when the motor is off. Is this normal? Do i need a new guage? Thanks guys!
 
Levinz11

Levinz11

Senior Chief Petty Officer
Joined
Apr 1, 2012
Messages
726
Re: 2 newbie questions

That "vacuum line port" should have a clear or yellow/clear hose on it, and run to the fuel pump.

carb3.jpg


My tach sticks, too. If I smack it will drop to 0 again. I plan on replacing it. It's had a good life at 24 years old.
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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50,405
Re: 2 newbie questions

post a picture of the "vacuum line port" and the carb. someone could have swapped in an automotive carb

regarding the tach, my old Avanti tach would drift up to about the 1000 mark when the key was off, however read accurately when the key was on. some gauges go to zero, some drift a bit without power. if the gauge reads correctly (verify with a separate tach like a tune-up tach) then your gauge is fine.
 
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blackstang932005

Seaman
Joined
Apr 1, 2008
Messages
50
Re: 2 newbie questions

Thanks for the quick responses. Im at work,but i will post some pics when i get home. On my carb it has a smaller vaccum line directly below the picture of yours with the clear line going to the fuel pump
 
B

blackstang932005

Seaman
Joined
Apr 1, 2008
Messages
50
Re: 2 newbie questions

Ive only had the boat a few weeks. Im not sure its history. Maybe that is an automotive carb.
 
B

blackstang932005

Seaman
Joined
Apr 1, 2008
Messages
50
Re: 2 newbie questions

i know im a noob but where does the clear tube end? Sorry I haven't received my manual yet.
 
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