How to safely check sight tube? (I know...it sounds obvious, but)

[gwa584]

Hi all -
I'm looking for advice on how to safely check my fuel-pump-to-carb sight tube. I know it sounds obvious (i.e. LOOK at it, it's a SIGHT tube), but mine has yellowed/darkened with age so I can't make out if there's fluid in it or not.

Is it unsafe if there is fuel there to just pull the tube end that connected to the carb and then tip it down to see if fuel drips out? Any suggestions (am I making more if this than need be)? I'm a newbie to boat ownership and maintenance and have a merc service manual to the engine but it just says "look at the sight tube".

BTW it runs fine right now idling/driving/accelerating so it's not flooding at the moment but wanted to head this off if there's an inbetween period of a fuel-pump starting to go and actually seeing it in boat performance.

Thanks.

Background:
I have a 1987 Four Winns 170 Candia deck boat with a 165hp Merc inline-4/224cid engine, with a close cooling system and an Alpha One Gen I outdrive. Serial numbers as follows:
- Mercruiser Drive Unit Serial #: 0B701774
- Mercruiser Engine Serial #: B731211

 

[gwa584]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

one more thing...though it does seem to run fine, it does seem to be sucking gas like it's going out of style. I don't smell anything when it's running and my bilge is dry...so could it just be dumping extra fuel through the system and out with the exhaust & raw water without having a noticeable impact on regular running? Thanks.

 

[bomar76]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

Ever consider coughing up the $2 for a replacement hose?
If your time is worth anything at all, you spent more than $2 of your time typing all that up.....
and yeah, if nothing else, pull the tube off at carb, hold it down throat of carb, and crank engine.
No fuel squirting=good diaphram.

 

[gwa584]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

But could it still run relatively ok idling and driving with a bad diaphram and could that chew through gas quickly without other noticeable effects if that's the case? Thanks.

 

[bomar76]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

Who knows...it is all subjective.
Sitting at the computer is never gonna tell you if it's bad or not, you are eventually gonna have to go out and look.

 

[Limited-Time]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

If the diaphragm ruptures the gas will flow up the tube and dump directly into the carb............................causing the engine to run like sheet.........................alerting you to a problem....................If the engine runs fine there's probably no problem...........................As for the Sucking Gas................thats what boats do.................the mileage is some where in the 2 to 4 mpg range.

 

[rad1026]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

In the same regard, not to hi-jack anything, is there a special type of tubing that needs to be used as a replacement? Is the clear tubing you find at the home supply stores suitable for that application or do we need to go to the marine supply to find it?

 

[bomar76]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

The cheap clear tubing from the hardware store is fine.....

 

[danond]

Re: How to safely check sight tube? (I know...it sounds obvious, but)

It has to be rated for fuel or it'll melt when the gasoline hits it.