vacum gauge

[renny1]

can someone give me step by step in laymans terms how i use my vacum gauge to set carbs up and check fuel pump on mercury inline 6 1982 115 hp thanks in advance

 

[Chris1956]

Re: vacum gauge

Renny, I have never seen a procedure to set the carbs on an outboard, using a vacuum gauge. There is a procedure to use a vacuum gauge to see if the fuel pump is operating properly, however, I do not know if a vacuum specification exists for the fuel pump on that model.

Usually we just rebuild the fuel pump, if we suspect it of malfunction. To test for malfunction, drive the boat at 3/4 throttle or more. if the motor starts to slow down or stall, have someone pump the primer bulb. if the motor speeds up or stops stalling, the fuel pump is likely bad, and should be rebuilt. Rebuilding kits are cheep.

 

[renny1]

Re: vacum gauge

no ive rebuilt the fuel pump and the carbs new gas tank compression al 120 new plugs new battery new solonoid bulb stays hard but the fuel enricher has a sort of thing on top that you can turn which i did but dont know where its meant to be set oh also new fuel line and bulb and i do have a manual any ideas i would be so graeful

 

[renny1]

Re: vacum gauge

but she still bogs down and is hard to start when warm
if i throttle her till she starts bogging then back off a bit i can sometimes get her to 4400 revs but not over 5000

 

[hkeiner]

Re: vacum gauge

A vacuum gauge can be used to check if the fuel pump is working OK and to check if there is any restriction in the fuel line upstream of the fuel pump. Either of these conditions can cause fuel starvation resulting in the symptoms you are experiencing. Mercury issued a service advisory describing how to use a vacuum gauge to test for these conditions. The trick is to monitor the vacuum in the fuel line while the engine is bogging to see if it goes out of spec at that time.

http://www.marinepartsman.com/Mercury-Marine-service-bulletins/Mercury-Mariner/2001/EN_17.PDF

 

[JUSTINTIME]

Re: vacum gauge

Renny, I have never seen a procedure to set the carbs on an outboard, using a vacuum gauge.

wow you never synced a honda or yami then?

 

[renny1]

Re: vacum gauge

wow you never synced a honda or yami then?

the box has a picture on it with it connected to a carb now in totally confused

 

[Chris1956]

Re: vacum gauge

Justin, I guess I should have added the word "Merc" before outboard. He is working on a Merc. Have you seen a procedure to sync a Merc Carb with a vacuum gauge? if so, provide it for us.

 

[JUSTINTIME]

Re: vacum gauge

nope, they do not have fittings for it

 

[rodbolt]

Re: vacum gauge

as a generic test tee your guage into the fuel system at the pump inlet, run the engine at or near WOT under normal load, anything less than 1/2"Hg usually indicates a weak pump or an air leak, anything over 4"Hg indicates a restriction.
the fuel primer bulb is on the suction side of the system and will never remain hard.
the solinoid black piece your describing is a manual overide incase the battery is dead or something.
push it in and its now priming the crnkcase manually for cold start.
normal symptom of a weak pump on a merc,let it idle for about 10 min ingear,nail the throttle, if it bogs repaet the test but immediatly prior to nailing it pump up the primer, if it now does not bog its most likly a failing pump.
best I recall the pump output presure at or near WOT should be about 3 PSI minimum.
can also be checked with your T fitting and pressure/vacum guage.

 

[renny1]

Re: vacum gauge

thanks for that info, i think i should have used punctuation. the solonoid is new, the fuel enricher has a long knob on it which cant be pushed in only turned one way or another from what i am understanding that would be a manual choke?????? so if it is working (which it is) should it be closed tight or open or half open

 

[AMD Rules]

Re: vacum gauge

Enrichment valve is normally closed. You should see an arrow on the top saying which direction to turn the knob. It is electrically operated by default, but can be operated manually my turning the knob on top.


.

 

[renny1]

Re: vacum gauge

thanks AMD rules thats the answer i needed as it is open hence i am flooding the engine all the time when starting as i am using electric choke