View Full Version : 43lx wonbt start after warm up
"I have a 1989 4.3LX(4bbl) Aplhpa one. I just changed plugs, wires, cap and rotor, fuel filter. Starts and runs fine in driveway. Starts great at the dock, let it warm up, once warm it won't idle, then it won't restart. Any suggestions? Thanks."
"Crack the throttle and try it. Clean you r flame arestor, too. That's the #1 neglected item I see on boats. #2 is probably old oil and filter. Next, if you notice a strong gas smell, remove the flame arestor and see if gas is dripping from the carb. That would indicate a leaky needle valve or leaky float. You may be flooded and need to clear it by going WOT while cranking it, and pulling the throttle back when it catches.
If it's hot where you are, vapor lock is a possibility, too. Open the motor box and turn the bilge blower on to see if it starts after cooling down for a few minutes. If the tank has been run dry more than a couple of times, your fuel pump impeller is probably worn and the pump may need replacing. Don't run it dry- ever. Did you check the fuel/water separator lately? How about the fuel tank vent?"
"Flame arrestor is clean. Oil and filter change last fall before storage. Air temp has been about 58-65. My sun deck is getting redone, so it is completely off, engine compartment is wide open. No gas dripping
A new distributer was put in due to the bolts holding the cap corroding and breaking off plus the shaft was corroded. So that was done. Timing was set to 8 BTDC. But this was set up at 1000-1200 rpm range. I was thinking maybe that had something to do with it since I got home tonight"
04-28-2006, 08:59 AM
How do I tell if the carb is flooding? Does it need to be rebuilt then?
What about the choke? I have the manual element choke bolted to the intake. I do not have the engine cover on(getting recovered)could this keep the element from warming up and not pulling off like it should when the engine is warm? Air temp is about 61-65.
"Manual element choke? What is that? Isn't your choke electric with a purple wire going to it? Should be on the side of the carb. If this is closed when starting hot, it either needs adjustment of replacement. If the choke thermostat is on the intake manifold below the carb, yes, these can go bad.
Have you checked for spark when it's hot?
I don't know how much you know about motors but if you are weak in any area (not trying to be mean), I would recommend getting a book on gas engine theory. It should answer a lot of questions and save you some money.
"You may be flooded and need to clear it by going WOT while cranking it, and pulling the throttle back when it catches. " This is from my previous post- have you tried it yet? If it starts, you were flooded. If you have to pump the throttle to get it to start, it's too lean or there's some issue with the fuel pump or system. Did you fill the fuel/water separator when you replaced it?"
My choke is a thermal element choke with a cover over it. When the it heats up the metal expands which pushes a lever up taking the choke off. Not trying to be mean but I have included a link showing the my carb setup along with the choke and linkage. Let me know what your take is on parts 36-40, no wire connection there."
"Link didn't show up:
http://18.104.22.168/mercruiser_oem/Mercruiser.asp?Type=13&SubType=111&A=37&B=1 2 ("")"
"I don't know when they went to electric choke but I have replaced a few of the kind you have (mechanical)- GM used them for decades. So, going by your post, it is opening the choke, right?
What else have you checked? You didn't say anything about checking fuel quality, whether there's a squirt of gas when you move the throttle, if you checked for spark, if it has points and if they're in good shape, etc. If it has points, what are they gapped at- also, the dwell should be checked."
"It has the Thunderbolt IV ignition. I think what is happening is the choke element is cooling off, causing it to choke the engine when it is warm. Fuel quality is fine, everything ran great the first time out when it was 75+ degrees. It has cooled off since.
My engine cover/Sundeck is getting redone, so I took it out without the cover just like the first time to fine tune a couple of things.
I still wanted to confirm if my timing needs to be set at 8 BTDC ata lower RPM then 900-1200"
"The timing may be on a sticker on one valve cover or the plastic cover on the flame arrestor but I thought it was supposed to be at 6 degrees BTDC. Also, IIRC, there are specific things you need to do in order to set the base timing but I worked with more Indmar motors than Mercruiser and I don't remember the Thunderbolt setup as well.
Regardless, your boat should still run at cold temps and a couple of degrees of timing shouldn't make this much difference. When you do get it to run and punch the throttle, does it make kind of a soft popping sound? If it does, one of the best things you could do is get a manual and look up carb setup. Mercruiser calls it either a "rich pop" or a "lean pop" and if it does it for either reason, it needs setup. I wouldn't do a carb setup or set the timing on a Mercruiser without a manual, just because I don't know the Thunderbolt ignition as well as I know the Delco and Northstar ignitions. A friend of mine just bought a Glastron with the same motor you have and we're trying to find a Mercruiser manual. I haven't read a Seloc manual yet, but since I have seen other aftermarket manuals with errors (Haines and Chilton), I prefer to go to the source.
I don't know if you know anyone at a Mercruiser dealership but a lot of times, once they know you, some dealers are willing to copy sections of service manuals. Mercruiser sends out tons of updates, they constantly change parts and if you need certain parts, be aware that the part number you give them won't necessarily be the current one because when they change a part or spec for that part, the number supercedes to the new one. It's frustrating for you as a customer but it drives people who order parts crazy. Getting to know someone at a dealership is a great resource. This isn't a great time of year to pick their brains, but if you get them at the right time, they'll usually help you out, if they're a decent dealership. ."
"Actually whe it is first started it runs smooth. It revs up no problem to 4500-5000 rpm. Like I said before, last summer and the first time this year it rean great. Wide open runs to idleing through the canals. One thing I might look into is an electric choke but I am not holding my breath. Once I get the cover back that should hold the heat in and keep the choke from cooling off too much.
The tag on my valve cover has 8 BTDC for the timing plus a few other things, WOT, Plug Gap etc. Thanks again"
"Once the engine warms up, the choke really doesn't need to do anything anyway. If it doesn't start next time, look at the choke plate and see if it has closed. If it has, you may just want to see if you can get another choke like the one you have. The electric one is marginally better and you'll have to mount it, wire it and adjust it.
Again, to make it easier to decide on a course of action assuming there's spark, open the throttle and see if it starts (flooded) or pump the throttle (too lean) and adjust the carb accordingly. It could just be gummed up, too. Have you ever used Sea Foam? It's a good fuel system cleaner and helps keep things moving freely."
04-30-2006, 12:02 PM
"I have a mercury 25 hp made in 2000 4 stroke the side of the engine says it is from family YM9XM when I start the engine it runs gas out of the carb, it is a pretty good size stream can't see exactly where it is coming from. a little gas drips from the air intake, any suggestions, I would appreaciate any help you could give me
"You should probably start a new thread in the OB section since nobody from that side will see it here unless they happen to see this thread. You'll be able to get info from the OB crowd faster.
Beyond looking for leaky hoses, and taking the carb off, how old is the gas and is the carb gunked up? If it is, it's not able to close the needle valve. It also may have a bad gasket."
04-30-2006, 12:37 PM
the gas is about 18 months old I put stabill in it and run the engine about once a month. I kind of suspect that it is the needle valve stuck. it there a way I can remedy that myself?
thanks for responding.
Your gas is too old. Drain the tank and use fresh gas with a fuel system cleaner (like Sea Foam).
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