Mercruiser 4.3L Alpha Gen 2 cold hard to start

[Fun Times]

You do not want to install a fuel priming bulb in a bilge.

While I've seen them installed on the forums and the convenience would be nice to have in a lot of boats with problems, The united states coast guard prefers you don't install them in a closed bilge.:boom:Or maybe they would? $$$.

PS, Be sure your lanyard kill switch at the shifter is on/in the run position..You may have turned it off so the engine wouldn't start during cranking... That or a bad fuse or connection someplace like ALLDodge mentions.

 

[alldodge]

From service manual 18

 

[bruceb58]

A neutral start safety switch will prevent the starter from operating. Maybe you meant the man-overboard switch.

 

[JustJason]

Can someone explain why I'm not getting voltage at the oil press switch (purple wire) with the key on??

Because without the engine running, there isn't any oil pressure to close the switch and complete a circuit.

I've read all the posts... Try not to overthink this. There are billions of carbureted engines out there that are not hard to start. If yours truly is that hard, then start from square 1....

1. Make sure you are starting it the correct way - If you are not, it will be hard to start.

2. Make sure the engine has good compression

3. Make sure the engine is in a good state of tune, and that the timing is spot on.

4. Make sure the carb isn't leaking down.

5. You have a low voltage issue that is making for slow engine cranking, or low voltage to the coil.

6. Make sure the quality of the fuel itself is good, and the fuel is reasonably fresh.

A carbs fuel bowl will hold enough gas to get it started for about a month. If you had hard starting but you only started the boat once every 3 months I can see the issue, the carb needs to re-prime. Other than that, if you are starting it multiple times within that month, then your problem is with one of the 6 items above.

 

[timjet]

Well stupid me, the safety switch on the throttle control was off. Thanks for pointing that as a possible reason. So once the safety switch was on the circuit tested as it should.

From my research here and on other forums I believe Chris is correct. The Weber 4BBL carb looses fuel after a couple of days and the engine is in a dry start condition. From my 17 years in owning this boat it didn't matter whether the outside temp was cold or not, the engine has always been hard to start after not using it for a couple of days. I live in Tampa, FL. Once started and warmed up it started on the first crank, and continued to do so for maybe 3-4 days.

This is a procedure I will try first before modifying my circuitry: http://marinemechanic.com/2000/answerman/hard_coldstart.htm

The above link along with Chris's very detailed explanation, and my experience confirms in my mind that this engine has a history of hard starting. If the procedure outlined in the link doesn't work for me, I will add a momentary switch to bypass the oil pressure switch, to be located at the helm, not in the engine compartment.I will forgo the squeeze bulb as a priming device.

I'll post my success or not using the above procedure and what I will do about it in a week or so.

Thanks to everyone who participated in this thread. I hope it's useful for anyone with a Merc 4.3L with the Weber Carb.

 

[achris]

As for the advice in that link.... Been there, done that, and much more.

I rebuilt my carb, many times, replaced the solid needles with sprung ones. Dropped the fuel level in the float chambers by 3mm (1/8"). I even had Merc replace the carb, complete. From the 9600 to a 9666S. No change. I eventually got so sick of the problems it was causing I started doing some serious investigation. I pull the carb and stripped it down, then set it up on the bench and filled the float chambers with fuel. I then blew a stream of air though ONE of the primary venturis and went to bed. The next morning the float chamber on the side I blew the air through was empty, the fuel laying on the floor under the carb. The side I didn't blow the air through was still full. So, I filled it again and blew the air through, curious as to how and where this fuel was leaking out. Mystery solved. Once the fuel was flowing up through the passages to the main discharge in the venturi it stayed flowing, I'm guessing by capillary action. I could see it dripping off the end of the venturi cluster!

Here's the really annoying part. I then spoke to Merc (I was a dealer at the time and had access to the 'brains trust')... I was told that what I was seeing was not possible... And that 'there is no problems with the Weber carbs'.... .And the phone put down in my ear.

I redid the tests and nothing changed. The carb continued to dribble, Merc continued to deny any problems... Stalemate.

I have since solved the problem... Bought an MPI engine, which actually had more problems than a dribbly fuel system :facepalm:, but we won't go into that here... What I should have done is trash-can the Weber and put a Edelbrock 1409 on....

Hope this helps....

Chris.....

EDIT: Guess what I just found? My very first iboats thread... It's all about this carb problem. If you do searches you'll come up with quite a few of them....

http://forums.iboats.com/forum/engi...-engines-outdrives/47151-weber-carb-on-4-3-lx

 

[fen-isl]

I have a 1996 4.3 with 2bbl carb and i have a momentary switch wired in from the battery to the pos wire at the elect fuel pump. 1st thing i do when i get in the boat is start the blower then push the switch for 1-5 seconds and she fires right up. The switch is spring loaded so it returns to a Normally open position when my finger is removed. Is there a better fix? Maybe but this works for me.

 

[achris]

I have a 1996 4.3 with 2bbl carb and i have a momentary switch wired in from the battery to the pos wire at the elect fuel pump. 1st thing i do when i get in the boat is start the blower then push the switch for 1-5 seconds and she fires right up. The switch is spring loaded so it returns to a Normally open position when my finger is removed. Is there a better fix? Maybe but this works for me.

You have a 2bbl carb, not a 4bbl... The 'dry carb' problem is only with the Weber 4bbl carbs....

 

[fen-isl]

Thanks Achris I was having same issue and thats how i fixed it. So on that note maybe i will have to recheck it out in the spring. Basically it would turn over for a long time before it sputtered to life. Added the switch set the choke with the throttle lever and tap the key and it fires up nice and smooth (almost like it was fuel injection) Only need to use primer switch 1st start of the day.

 

[JoLin]

Because without the engine running, there isn't any oil pressure to close the switch and complete a circuit.

I've read all the posts... Try not to overthink this. There are billions of carbureted engines out there that are not hard to start. If yours truly is that hard, then start from square 1....

1. Make sure you are starting it the correct way - If you are not, it will be hard to start.

As elementary as this seems, it's important. My Carver has twin 4-bbl 4.3 Mercs in it, and when I bought it last year I had a tough time starting it from cold. I started it the same way I used to start my old carbed cars back in the day- pump the throttles a few times, set it halfway open... and I'd crank and crank before the motors would fire. Well, when I finally tried just setting the throttle without pumping it AT ALL, the engines fired right up. I was flooding it every time without knowing it.

My .02

 

[timjet]

After a couple of months experience I've found an easy way to start these engines. As described in a link I posted above the procedure I use to start a cold engine is to crank the engine over until I see oil pressure on the gauge and release the key to run - not off. The fuel pump will run until oil pressure reduces to 0. I do this again. On the 3rd attempt I pump the throttle twice and leave it about half way open. Generally on the 3rd attempt the engine starts right up.

A momentary switch to by-pass the oil pressure switch and run the fuel pump does the same thing but is really unnecessary.