RESOLVED-just rebuilt carb- hard to start when warm after sitting

[sltintexas]

I just rebuilt my carb. I had some serious idling problems and bogging prior to rebuild. It is running alot better. i suspect I am still missing something on my carb adjustments.

After it warms up I can shut down the motor and start it back right away with out issues. If it sits a while, it will need me to move throttle to wide open and it will start after lot of cranking.

Do y'all think its the idle air mixture? I had a hard time trying to figure that out.

Anything I could have done with the carb rebuild that is a little off?

I still have just a small hint of hesitation when I "gas it" from idle. Don't know if this is related or not. The problem of hesitation is much much better though.

motor is mercruiser 3.0LX 1996 serial number ok148861
mercarb 807504

 

[Black as]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

I would check the needle and seat, the float level and fuel pressure 1st.

 

[novausc]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

I'm having a similar issue after mine was rebuilt. Let me know if you figure anything out and I will do the same.

 

[jtmarten]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

Float level too high? Sounds like fuel is leaking into the venturi. One way to tell is once you shut it down, pull the flame arrestor and watch the carb for a while. Another possibility is that the carb is heat soaking, which increases the pressure in the bowl, forcing fuel through the main circuit.

 

[CHEVYJEFF]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

common problem w/ pos mercarbs. been there done that. get used to it

one problem is the ethanol in gas these days boils at a lower temp then the pre ethanol gas so when your sitting after running gas is boiling and leaking down the carb.

To start after running and hot hold throttle only button in and put throttle to wide open and start engine, pull back as soon as it fires. This is typical starting procedure for a mercruiser after running.

You can also open the hatch and let the engine cool for a few min after running to help. I have had to go as far as throwing some ice on the intake after sking for a long time on a 100 plus degree day here in dfw as the carb volcanoed on me.


I rebuilt my 2 bbl mercarb chasing this problem. I followed the instructions that came w/ the serria kit for setting the float. I think it was a 10mm spec. from a dot on side of float to the carb body. I used the little ruler the kit came with. I found that setting the float with the carb case gasket in place and using it as the dimesion line was prefered over setting it without the gasket in place. Makes it a little more lean setting. The carb ran too rich when I originally had it set without the gasket as a base line. Once I reset it with the gasket in place it idled better and was a little easier to start.

I am in process of trying to make a phenolic spacer to go between carb and intake to keep the carb from becoming so hot. But that project is destined for the winter to do list.

 

[[OBC]Patch]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

I am in process of trying to make a phenolic spacer to go between carb and intake to keep the carb from becoming so hot. But that project is destined for the winter to do list.

That is what that spacer was for!!

 

[sltintexas]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

Thanks for everyone's help.

I'll give you a brief history prior to rebuild. I bought boat and it has been sitting for about 2 years. It had some hesitation but started and ran otherwise without issue. One day out on the lake it ran like crap. Kept stalling horrible bogging. so that is why i rebuilt.

I would think (but could be wrong) that if it was something related to heat, that I would of had that issue before. Besides the running like crap that one day it started beautifully.

I will start with checking the float level again. If I had to be a little high or low, which would be better? Its not the easiest thing to measure with those ruler things they supply. I thought I was right on the $$ though... and I did acct for the gasket when I measured (I think).

One question on the idle fuel adjustment. when I was turning it one way, I did notice the carb made more of a vacuum noise. It seemed to still run fine. any input? It seemed like I could turn it quite a ways in either direction before it started run rough.

 

[CHEVYJEFF]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

for the idle screw I usually start w/ 1 1/2 turns out from snug then listen for the highest rpm i can get by going out 1/2 turn at a time. This way as soon as max rpm is reached I go one more 1/2 turn out and call it good. The vacuum sound you hear is the amount of air going thru the idle passage. more vaccum sound the more air going thru. you may not have it set just right hence your of idle heistation. Also check your choke make sure its fully open once its hot. I assume you have done all the other tune up basics, fuel filter, cap and rotor, plugs, wires.

 

[jtmarten]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

I am in process of trying to make a phenolic spacer to go between carb and intake to keep the carb from becoming so hot. But that project is destined for the winter to do list.

Do they not make them for 2V's? They're available in all shapes and sizes for 4V's.

Edit: Did a quick check on Summit: http://www.summitracing.com/search/...uretor-Mounting/2-barrel/?keyword=carb+spacer

 

[CHEVYJEFF]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

Do they not make them for 2V's? They're available in all shapes and sizes for 4V's.

Edit: Did a quick check on Summit: http://www.summitracing.com/search/...uretor-Mounting/2-barrel/?keyword=carb+spacer

nope the wonderful 2bbl mercarb is its own little pos. copy of the rochester but different enough nothing will fit it. I will someday just put a edelbrock intake and a holley 600 on it and use it as a fish lure

 

[sltintexas]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

thx chevyjeff. I just noticed you were in wylie..and all my boat testing is on Lavon right in your backyard!


I haven't done full tune up yet. I do a little bit every weekend. I have done plugs but not wires or cap yet. Filter was changed when carb was rebuilt. I have a water seperator ready to install as well.

Choke was wide open when hot.

 

[sltintexas]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

took it out briefly this evening and fiddled with the idle mixture needle. I didn't get to play much as it started raining..but I think I made some progress. I shut it off for a while and it didn't give me any problems starting back up. hopefully this weekend I'll be able to let it sit for 30-40 minutes and see how it does.

Acceleration with out bogging down seemed to improve as well. More testing needed though.


My cold start sucked. I noticed my choke wasn't closing.. yesterday it did, so I'll have to investigate that.

 

[sltintexas]

Re: just rebuilt carb- hard to start when warm after sitting

Re: just rebuilt carb- hard to start when warm after sitting

SUCCESS! Cold start was perfect. Pumped it twice, left it at about half throttle and it fired right up.

I kept it at about 1500 RPMs for about 20 seconds and it idled fine.

Tooled around the lake. Lots of stop and started. One time I had a very brief hesitation but that was the only time. All others were great. Had a few WOTs that were great! Stopped to let the kids swim for about 20-30 minutes and afterwards it started right up.

All in all I think my rebuild was a success and I'm running way better than before! Thanks for everyone's help.