Merc 3.0LX starting issues

[curt2199]

I've had these issues since I acquired the boat last year. Its a 94' 3.0LX motor with the mercarb. The engine will generally not start cold or hot without holding it WOT and will run great after started. The fact that my throttle only button is broke makes the problem worse as I have to have someone crank it over while i hold the throttle open at the carb. Many times it will fire cylinders while cranking without any hands on throttle but just not take off and run without being held wide open. Last year I did all new ign parts from plug to rotor, batts, fuel filter, and rebuilt the carb with a sierra kit and set everything by the instructions in the kit. Also did s new float with the kit.

 

[dubs283]

Re: Merc 3.0LX starting issues

are you familar with the procedure for starting a carb engine??

not having the ability for throttle only really makes it difficult, you should definitely fix that issue - it willl make starting your engine very easy

 

[curt2199]

Re: Merc 3.0LX starting issues

Yes, pump it 3 times when cold to set the choke and get some gas in it. I do that normally and it still doesn't start until I go back and give it wide open throttle. The choke appears to be working correctly from what I can tell because it will close when cold and gradually open. I can also see gas squirt from the jets when I give it throttle.

 

[Don S]

Re: Merc 3.0LX starting issues

I do that normally and it still doesn't start until I go back and give it wide open throttle.

Why don't you just open the throttle up when cranking it, no need to go back to the carb.
Just use the throttle only button on the control. Then you have complete throttle control while still in neutral.

 

[curt2199]

Re: Merc 3.0LX starting issues

Throttle only button is broken. I have a new one ordered and should be here soon but even pushing in on whats left of the button plastic shaft, I can feel it click into place like its doing somethinf but it never releases the gear shift so I'm going to need to pull it apart when I get the new button and see why its still not working. The controller is the commander 3000 with the button that is flush and built into the lever

Aside from that, it seems odd that I'd have to hold it wide open to get it to start.

 

[Bondo]

Re: Merc 3.0LX starting issues

Throttle only button is broken. I have a new one ordered and should be here soon but even pushing in on whats left of the button plastic shaft, I can feel it click into place like its doing somethinf but it never releases the gear shift so I'm going to need to pull it apart when I get the new button and see why its still not working.

Aside from that, it seems odd that I'd have to hold it wide open to get it to start.

Ayuh,... That would lead me to believe that the carb rebuild was a failure,....

Odds are, it's floodin' itself... But ya gotta Check to see...

 

[Don S]

Re: Merc 3.0LX starting issues

Throttle only button is broken.

Yeah, I missed that.

FIX it !!!!

 

[curt2199]

Re: Merc 3.0LX starting issues

I started with the shift controller last night as the new throttle only button came in. I pulled the controller off and apart and am not quite sure how to get the new button to disengage the shifter. The old button was broken but the plastic shaft was still there and would push in and do something but still wouldn't disengage the shift cable. I'm thinking I may end up having to disassemble this linkage to find out why it's not disengaging.

 

[Don S]

Re: Merc 3.0LX starting issues

Post a picture of your control.

 

[curt2199]

Re: Merc 3.0LX starting issues

This is a picture of the controller that I have. It's not my pic as I'm at work but the exact same controller. Mine does have the trim switch where the blank spot is on this one on the handle. I can get pictures of mine tonight if needed.

 

[Don S]

Re: Merc 3.0LX starting issues

Here's the manual for that control.

Commander 3000

 

[curt2199]

Re: Merc 3.0LX starting issues

Great, Thanks! Also, has anyone had any better ideas for re-mounting these controllers. Why they use screws into wood on a boat is beyond me as I have one completely rotted out and the other 2 are just ok. I thought about trying to make a metal bracket to bolt to the wood and then use machine screws into the bracket to hold the shift controller. The way it has been I get some movement when shifting.

 

[Don S]

Re: Merc 3.0LX starting issues

The controls normally come with through screws with nuts for mounting. The boat builder just cheaped out and used screws because it's faster. Screws work fine in new wood.

 

[Levithan]

Re: Merc 3.0LX starting issues

Sounds as though you may be putting to much fuel in the carb when starting as well(having to wot the throttle is how you clear a flooded engine).
There is no need to pump it 3 times(to much fuel for a small 3.0L) once to set the choke is all she should need then leave the throttle arm about 1/4, when running smooth, back the throttle off to neutral.
My 3.0L only takes 1 to 1.5 pumps and she fires right up everytime with minimal cranking.
When hot it should start in neutral with no throttle if the carb is setup correctly.
If you are pumping when hot that is definetley a no no.

 

[curt2199]

Re: Merc 3.0LX starting issues

I've tried different pumps from 1 to 3 and it doesn't seem to matter when cold as it just won't start. It'll fire 1-2 cylinders in succession but not kick over and fully start unless I WOT. It's like it really wants to start, it just won't.

I don't normally pump it when hot either and if I just shut it down within the last 15 min or so then it'll start back up without WOT. If it sits for more than 15-30 min from shutdown then I'll have to WOT to get it to start. I may pull it off tonight and pull it apart and check the float level.

Should the gas normally squirt out in a stream or have more of a spray pattern? Right now it shoots out in a stream when I give it gas.

 

[kd7isf]

Re: Merc 3.0LX starting issues

...Last year I did all new ign parts from plug to rotor, batts, fuel filter, and rebuilt the carb with a sierra kit and set everything by the instructions in the kit..

Check your firing order... Odds are your WOT power is pretty low too..

You said you replaced all the ignition componenets. Did you replace the spark plug wires by swapping one at a time? Or did you pull them all off and then use the info on the spark arrestor as a guide?

I'd guess you used the info on the spark arrestor as a guide... Which in the case of the 3.0LX is known to be bad. There is a factory service bulletin on this. Call merc, give them your serial number, and they send you a new sticker..

I came across this the hard way..
Proper firing order for 3.0lx is 1-3-4-2
Many flame arrestors on these engines were INCORRECTLY MARKED 1-4-3-2.

It will be VERY hard to start and have a very low WOT if you run it with the wrong firing order..
And it will quickly blow out the side of the head gasket, usually on the #3 cylinder...

Hope this helps...

 

[curt2199]

Re: Merc 3.0LX starting issues

I replaced one at a time and WOT is about 4300 rpm at 38mp. It efinitely doesn't have a a wire switched or it'd be running like crap. It runs great other than the hard start. I'm sure its something to do with the carb rebuild and the throttle only button just amplifying the problem. I had a regular mechanic rebuild the carb for me and he'd never rebuilt a mercarb before.

 

[kd7isf]

Re: Merc 3.0LX starting issues

I replaced one at a time and WOT is about 4300 rpm at 38mp. It efinitely doesn't have a a wire switched or it'd be running like crap. It runs great other than the hard start. I'm sure its something to do with the carb rebuild and the throttle only button just amplifying the problem. I had a regular mechanic rebuild the carb for me and he'd never rebuilt a mercarb before.

Agreed. You would not get anywhere near that much power with the firing order wrong...

Sounds too me like you either have too much fuel (not the case if you have to pump it more than once or twice to get it to start) or not enough to get it to start. Probably choke related. When cold, the choke should stay shut and have moderate spring tension holding it shut. It should NOT open with throttle. As it warms up it should open..

Check your choke linkage and then follow the procedure in the mercruiser manual to set the choke spring. At this point I'd guess your choke is not closing all the way. Try this: pump the throttle twice, then hold the choke shut (by the linkage) and have somebody try to start it. If it starts right up, your choke needs to be adjusted...

Any mechanic that knows how to rebuild a carb can rebuild a mercarb. They are very simple.
The problem is finding a mechanic that A. knows what a carb is anymore, and B. knows how to repair them.


hope this helps..

 

[curt2199]

Re: Merc 3.0LX starting issues

I'm just now getting back to this issue after a hiatus from boating due to some family things. I have made a lot of progress on the issues that I had though...

First, I noticed that the venturi's were dripping fuel at idle and after shutting off the engine. I pulled the carb apart and checked the float level and it was way off. I adjusted it to 14mm for spring loaded needle per the merc manual that I could find and checked that the drop was at 27mm. I didn't get a chance to check if it fixed the drip because I lost daylight but I put it back together and it seemed to start easier.

Second, the choke was not in the correct place and the flap was always open. I fixed that and it's help with the cold start.

Third, I checked the timing with a light. I jumpered the two white wires at the distributor and disconnected and connected together the shift interrupt wires. I found that the base timing was at around 3-4 degrees ATDC. I backed it off to 1 degree BTDC and tightened down the distributor. It seems to be running much smoother but after disconnecting the shift interrupt switch I the engine idled back up and the timing jumped to around 14-16 degress BTDC. That seemed high but now that I'm thinking about it, the engine RPMs were up to around 1000-1100 rpm and the engine advances timing with RPM so maybe that is about what it should be for that RPM. I've lost all daylight and need to let it cool overnight but am going to try giving it a start in the morning and see if it fires up easily.

Also... that stupid throttle only button is fighting me. I bought a new button to replace the broken when it put it in and it will click in when pushed but still does not release the gear shift allowing throttle only operation.

 

[curt2199]

Re: Merc 3.0LX starting issues

I went out this morning, pumped the throttle once to start and it fired right up in 2-3 cranks so it sounds like I've take care of the engine issues, now to fix this stupid button.