3.0 Mercarb questions

[gwgautney]

I have a 1986 3.0 with a Mercarb on it. I just had it rebuilt a couple of days ago. When I got the boat there was a nipple or vacuum connection on starboard side towards the top of carburator that was not hooked to anything. What is this and where does it go. Second question is about the choke. I cant seem to get it set right. How would I go about setting the choke up its an electronic choke. Thanks and let me know if more info needed.

 

[cr2k]

Re: 3.0 Mercarb questions

That nipple is where the safety line from the fuel pump goes.

Set the choke (cold) to just close.

 

[gwgautney]

Re: 3.0 Mercarb questions

ok cool i saw a tube running from the fuel pump but it didnt go all the way around to the carb. i will get some new tubing and run it to it tomorrow. how much spring should be on choke. really a newb to all this

 

[thumpar]

Re: 3.0 Mercarb questions

To set the choke you push the throttle forward. What I would do on my 2.5l is push the throttle forward and back, then put it in throttle only and push it just past the 1/4 throttle click and start it. Worked every time. It might not be by the manual but my boat liked it.

 

[Fun Times]

Re: 3.0 Mercarb questions

Second question is about the choke. I cant seem to get it set right. How would I go about setting the choke up its an electronic choke.

Hi there, first see page 5B-27 for the the correct way to install the choke then see 5B-8 to adjust.

http://www.boatfix.com/merc/Servmanl/13/13B5R2.PDF

 

[Silly Seville]

Re: 3.0 Mercarb questions

Make sure you check the fuel barb coming out of the pump for blockage. It is there to pass fuel to the carb in the event of a fuel pump diaphragm failure. Use clear hose. If you ever see fuel in that hose, it means your diaphragm is failing. The rubber parts in old boat fuel systems do not like modern gas. Do not be surprised if you lose a fuel pump in the first or second season. There are fuel pump rebuild kits available. Do not use an automotive pump when yours fails! Auto pumps drain to the atmosphere...meaning the bilge of your boat.

 

[Fastatv]

Re: 3.0 Mercarb questions

Nice link....I needed it also. Thanks Rick

 

[gwgautney]

Re: 3.0 Mercarb questions

ok got another question.... I cant get this thing to idle and cant seem to get the choke set up right. I was looking at some pictures of other mercarbs and on the choke shaft where it ties into the rod that goes down to the idle screw the tang is pointing down. After looking at mine the tang is pointing up and towards the other side or port side of carb. Would this effect the carb. It seems to me like that would act somewhat as a counterweight. maybe im shooting long i dont know i just know it was just rebuilt and that is the way it was previously before the rebuild if i remember right. when i think i have it idling good its like the motor starts to die down after staying at that idle a minute or two. and the funny thing is it is never the same one time i get it cranked and its at one speed thr next time its at another speed Im about at my wits end HELP HELP HELP and one more thing when i do get it to idle its rough motor bucks some

 

[thumpar]

Re: 3.0 Mercarb questions

Have you done any other diagnostics? I would suggest a compression check just to make sure the engine is healthy.

 

[gwgautney]

Re: 3.0 Mercarb questions

Have you done any other diagnostics? I would suggest a compression check just to make sure the engine is healthy.

Havent yet but borrowed a gauge from a friend and plan on doing that this week. could you give me a rundown of how i need to do it and what compression should be around.

 

[gwgautney]

Re: 3.0 Mercarb questions

Ok so I did compression test tonight from front to back it was 110, 120 120, 110. Plugs were black and smutty and I just replaced them several weeks ago. Where to now any ideas?

 

[Fastatv]

Re: 3.0 Mercarb questions

Adjust the choke all the way off. Pump the throttle a couple of times, start in on the muffs. May die a time or two, just pump the throttle a couple of times when it does, start again. Bring the throttle up to about 1,000 rpms, let it warm up for say ten minutes, Bring the throttle back to idle. Make sure the choke is off of the fast idle cam. Using the idle set screw, adjust idle to 700-750. Now adjust air/fuel mixture screw to where u have the highest...clean idle. Then go back and adjust your idle again. This should get you in the ballpark however, idle speed should be checked again after the boat is in the water. It will change a bit when in the water due to the exhaust experiencing back pressure. Anyway, hope this helps you. Rick

 

[81 Checkmate]

Re: 3.0 Mercarb questions

No expert here but it still sounds like carb issues. Black sotty plugs.....Take plugs out and clean them to get it running right then get a new set when you are done.
Read thru the manual again and maybe take carb apart again and recheck everything...including re-setting the float drop.
Set choke plate as it say's in manual.

Not much to the 2 barrel carb.

Compresion test #'s look good

 

[gwgautney]

Re: 3.0 Mercarb questions

Thanks I will try those things this weekend I'm hoping its only carb really guess thats all it could be

 

[81 Checkmate]

Re: 3.0 Mercarb questions

Let us know the out come.

Good Luck!

 

[gwgautney]

Re: 3.0 Mercarb questions

When I get the motor to run its knocking some