Mercruiser 4.3 Missing
- Thread starter BillK
- Start date
- Joined
- Jan 1, 2000
- RO Number
- 775
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Charlie - that's the thing, I don't know what fixed it. The only thing I found really wrong was the electric choke wire loose. My guess is the connection was loose and it was allowing the choke to shut partially - that all I can figure.
- Joined
- Jan 1, 2000
- RO Number
- 775
- Messages
- 1,222
Update: Well, the surging problem came back after another 2-3hrs of running. Having pretty much gone through everything (electric/ignition/fuel filter, tank line) I went with my initial feeling that this was fuel related. Pulled the carburetor and wala! The float bowl was full of crap! Mainly varnish type gunk - but some big enough pieces that when I hit waves etc it would slosh around in the bowl and obstruct the power valve at the bottom of the bowl. That's why spraying carb cleaner down into the float bowl fixed things - until it sloshed around again. So, I have the carburetor apart, mainly going to clean it up, but also replacing the float, accelerator pump, the power valve and idle jet (ordered a kit this week). I have not rebuilt a carburetor since the Holley on my old Correct Craft, but this looks pretty simple. Gotta love the simplicity of an old carbureted motor.
- Joined
- Jan 1, 2000
- RO Number
- 775
- Messages
- 1,222
Update: So I took the carburetor apart, cleaned it and replaced the float, float needle, power valve, accelerator pump and idle jet. Put it back on the boat Sunday and it pretty much fired right up. Fine tuned the idle adjustment and it seems to run pretty good. Smooth right up to WOT - no hesitation or surging. If anyone has one of these carburetors and is hesitant to work on it, I found it to be very simple and easy to rebuild.
A couple of funnies:
1. When I was trouble shooting I took the top half of the carb off to look into the float bowl - Once I saw how dirty it was went ahead and removed the carb. HOWEVER, in the process the float and needle fell out - I found the spring and retainer pin laying on the manifold. Later while rebuilding the carb I realized there was also a small brass pin that hold the spring in the needle. I stressed for two weeks wondering where it was - fearing it somehow fell down the intake. Luckily I found it Sunday laying on the manifold - not sure what I would have done if I had not found it. I can't imagine even a brass scree that small would be good in a cylinder.
2. When I first tried to fire up the motor it cranked for a few seconds, could hear the fuel pump running. It fired and then died and would not start. A little starting fluid and it fired - then died. I little gas down the carb throat and it fired - then died. I'm about to start tearing the carb apart again - AHH maybe some gas in the tank - the darn thing was out of gas - poured 5 gal in and off she went. I do need to check this out again - it was low on fuel but surprised there was not enough in it to crank up - wondering if when I pulled the pickup out of the tank earlier if it is in there and not laying on the bottom of the tank or something.
A couple of funnies:
1. When I was trouble shooting I took the top half of the carb off to look into the float bowl - Once I saw how dirty it was went ahead and removed the carb. HOWEVER, in the process the float and needle fell out - I found the spring and retainer pin laying on the manifold. Later while rebuilding the carb I realized there was also a small brass pin that hold the spring in the needle. I stressed for two weeks wondering where it was - fearing it somehow fell down the intake. Luckily I found it Sunday laying on the manifold - not sure what I would have done if I had not found it. I can't imagine even a brass scree that small would be good in a cylinder.
2. When I first tried to fire up the motor it cranked for a few seconds, could hear the fuel pump running. It fired and then died and would not start. A little starting fluid and it fired - then died. I little gas down the carb throat and it fired - then died. I'm about to start tearing the carb apart again - AHH maybe some gas in the tank - the darn thing was out of gas - poured 5 gal in and off she went. I do need to check this out again - it was low on fuel but surprised there was not enough in it to crank up - wondering if when I pulled the pickup out of the tank earlier if it is in there and not laying on the bottom of the tank or something.
I just read through this thread for the first time and I don't see any mention of the anti-siphon valve. It should be located at the top of the pickup tube just before the fuel line going to the engine/filter/whatever. There is a stainless steel ball and spring inside to prevent fuel from siphoning out of the tank in case of a fuel line leak. Suction from the pump is needed to allow the flow of fuel. Sometimes the ball/spring can get blocked with junk and restrict the fuel flow. Remove and replace or just clean out with carb cleaner. One more think to look at in case the problem returns...or before it does. Another cause not previously mentioned is a blocked fuel tank vent. Temporarily removing the fill cap is a test for that. You have a relatively small fuel tank so why not see if someone can give it a good cleaning. Get that E10 cause junk out of there. Good luck!