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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3734
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Engine turns over but doesn't start. Engine turns over but

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Engine turns over but doesn't start.
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.
Customer: Engine turns over but does not start
JA: Is there anything else the Marine Mechanic should be aware of?
Customer: No

Hello, my name is***** will assist you.

What is the make and model you your engine?

Customer: replied 2 months ago.
Mercruiser 4.3L

I am going to have to decline the call for now.

Do you have the serial number of your engine?

How long has the boat been sitting?

Customer: replied 2 months ago.
It has been sitting for about 4 months in the garage since last on the lake
1a630729- serial

When you turn the key on, do you hear the electric fuel pump run?

Customer: replied 2 months ago.
I hear it engage when I flip the kill switch on

Ok great. Have you tested the fuel for water, and how is the oil level on the engine?

Customer: replied 2 months ago.
Oil level is good - have not tested for water on the fuel - how can I do that?

Remove the spin on fuel filter and dump it into a glass jar. Allow it to settle. If there is 2 layers in the jar, it has water.

Customer: replied 2 months ago.
When you say spin - you mean the filter or plastic connection before the filter

The filter looks like an oil filter, just it is in the fuel line. Mounted low on the left side of the engine when looking down at it.

Customer: replied 2 months ago.
Oh sorry read it wrong the Spin on fuel filter - not the spin - copy that thank you

Let me know what you see there.

Customer: replied 2 months ago.
Having an issue getting it off - may take a minute

No worries, There are no time limits here.

Customer: replied 2 months ago.
I am not able to get it off with my hands I will have to go to the store and get a tool to remove it

A standard oil filter strap wrench should get of out, provided the O-ring was oiled before it was installed.

Customer: replied 2 months ago.
That was what I was going to get I wil reply once I get it off

Sounds good. I will be on for a few hours more tonight.

Customer: replied 2 months ago.
Sorry for the delay busy at work and finally got a chance to go and get the filter wrench and drained some gas and it did not separate - looks like and smells like gas

Great. You will need to test the engine for spark using a sealed adjustable gap tester. This is the same one that auto techs use. Test from the coil to the dist and then each plug wire. Your issue may just be that a tune up needs to be done. This would include new cap, rotor, wires and plugs.

Customer: replied 2 months ago.
Ok will look at that next -thank you

Your welcome. Make doubly sure that the kill switch in fully inplace and on. That would also make the engine not start.

Customer: replied 2 months ago.
Would the fuel pump engage if the kill switch wasn't working ? When I flip it up to run I hear the fuel pump engage

Yes the kill switch is working.

Customer: replied 2 months ago.
Can I get a gap tester at autozone ?

Yes you can. It is the inline one with a glass case to enclose the spark. Set it to 7/16"

Customer: replied 2 months ago.
I got the tester and went from the coil to the cap and all of the spark plug wires as well and the tester lit up every time. What next?

Ok, you have spark, there are two other items needed for the engine to start. Compression and fuel, I would start with fuel since it would be so rare for all 6 cylinders to lose compression that the engine to not start.

If you have a can of starting fluid. Spray some inside the carb, put the flame arrestor back on, then try to start the engine. It should at least try and start on the fluid. You could also use a bit of gas if not spray is available. If it does try and start, I would remove the carb and clean it. Also make sure that the auto choke is working on it.

Customer: replied 2 months ago.
I assume when you say flame arrestor you mean the air filter?

Yes that is it.

Customer: replied 2 months ago.
Ok so poured some gas into the carb put the air filter back on and started it - but it would just turn over - never fired. How do I check the automatic choke ?

It is connected to the front of the carb, you should feel it get warm when cranking the engine over.

But with fuel in the intake, it should have at least hit, or tried to hit.

Have you looked at the spark plugs? I would be interested to know what the tips of them look like.

Customer: replied 2 months ago.
I have not pulled them - I guess that is next to try

If they have been in the engine for several years, replacing them is not a bad option.

Customer: replied 2 months ago.
I uploaded a picture of the plug I just pulled - by the looks of it this might be the issue - what do you think?

Have you checked the gap on that plug. Looks pretty large.

Customer: replied 2 months ago.
What's the spec?


Customer: replied 2 months ago.
I changed all of the plugs - gapped of course- still not firing. Weird question will it not fire if I don't have running water hooked up? Normally I do but haven't during our conversations since I was just trying to fire it not actually run it.

The engine will fire with no water hooked ti it.

Remove the flame arresstor and the connector for the throttle cable on the side of the carb. Looking down into the carb, with the key off, Move the throttle lever on the carb from its stop to full throttle. See if there is any fuel being sprayed from the two jets in the center of the carb. If there is not, it is just not getting fuel.

Customer: replied 2 months ago.
Ok did that and don't see/smell any visable gas - how would I fix that? The fuel filter had gas in it.

There is a filter on the inlet of the carb where the line attaches. Make sure that it is not clogged up.

Customer: replied 2 months ago.
Took off the line cleaned it out - attached it back - still don't hit. Took the same line apart at the filter didn't have any gas in it by the way which I thought was weird. Reattached it still won't hit- pour some gas in the carb and it hit - I didn't let it fully start since I was hooked up to water. Maybe the gas isn't getting out of the filter? Since the line seemed to be empty? Just a thought wouldn't hurt to change it I guess anyway huh?

Remove that line from the carb, hold it into a container to catch fuel. Have a helper crank the engine over and see if you can get fuel to the carb. That electric pump may not be drawing fuel from the tank. If that is the case, I would suspect the anti-siphon valve on the outlet of the tank, or a closed valve. to inspect the valve, you would need to remove the fuel line and then unscrew it from the tank pick up.

Customer: replied 2 months ago.
Actually was able to get gas to the carb through the line so it wasn't clogged but still not getting a hit - I guess now it has to be the choke?

Is the carb now shooting fuel if you try the throttle arm on it like before?

Customer: replied 2 months ago.
I took the arm off and working the throttle from closed to open and nothing is coming out

The floats are stuck inside the bowl. You can try to free them by tapping on the carb bowl with the wooded handle of a hammer. If that will not work, the carb will need to come off and be cleaned.

Customer: replied 2 months ago.
When you say the carb bowl - do you mean the front part of the carb?

Yes, it that area.

Customer: replied 2 months ago.
Ok that didn't seem to work - so when I need to take it in for them to pull the carb to clean it - or something that I can do?

If you are really handy with tools, you could do it, but you would need a gasket kit for it and should replace the needles as well.

Customer: replied 2 months ago.
I got adventurous and took the screws off the top and popped it - used to work on my 65 mustang as a kid. So the needles are the long things with the springs? What kind of carb is this to get a kit at autozone can I find the needles there as well ?

The needle is part 14. The one with the spring is the accel pump. Part 15. the carb is made by Mercury, most auto parts stores will not have a kit for it.

Customer: replied 2 months ago.
Ok cool I will get those ordered . The needle actually fell out into my hand when I pulled it off the float. Thank you for all the help

Your welcome. I hope that you can get out there soon with it.

Customer: replied 2 months ago.
Is the needle suppose to be a solid piece? Wonder if that was what was the issue. Anything I need to lube up the inside once I get everything before reassemble? Hope to get it out season as well !

The needle itself is one piece, the set comes with the seat as well as the needle.

Charles and other Boat Specialists are ready to help you
Customer: replied 2 months ago.
just got all of the parts and put them on the carb - but the gasket is wrong. It lines up on the bottom but not even close on the top. Can I get that at a local tracker marine shop or have to reorder?

See if they have gasket###-##-#### That is the one that you need.

did you clean all of the passages in the carb?

Customer: replied 2 months ago.
I cleaned them - I will stop by there tomorrow as they are closed for the evening

Ok. Let me know how it goes.

Customer: replied 2 months ago.
got the correct gasket and put the carb back together and back on the boat. Battery is dead from all of the attempts to start the boat, but def can hear the jets spraying gas into the carb so that's a step in the right direction.

That is a very good step in the right direction. Lets hope that you can get on the water this weekend.

Customer: replied 2 months ago.
Ok battery is charged and engine will turn over, still not firing. If I move the throttle and spray some gas into the carb it will firing and act like it will start but then won't and once that has burned off it just turns over. Any ideas?

Make sure that it is building oil pressure. There is an oil pressure switch on the side of the block that will cut spark if it pressure is not there.

Customer: replied 2 months ago.
The gauge builds up to around 40 psi when I am cranking the key - is that correct?

that is correct. Have you tried to advance the throttle when cranking to get more fuel and into the intake.

Customer: replied 2 months ago.
I even have gone as far as disconnecting the throttle arm and having my wife turn the key as I manuelly move the throttle- it will fire but not start completely- any thoughts ?

You are positive that you have spark on all 6 cly?

Customer: replied 2 months ago.
sir just ran through them all again with the tester and the light would blink on every attempt to start

Ok, do you have a separate fuel source that you can try. The fuel in the boat may be the issue. Dump the fuel filter on the engine, hook a tank to the inlet of it. And then crank the engine some. It will take a few to get fuel into the filter and into the carb.

Customer: replied 2 months ago.
Did that hit a couple of times but never started - throwing in the towel and going to take it to the dealer to have them look at it - thank you for your time

Your welcome. I know that it has to be close to starting. Possibly something like a small carb adjustment.

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