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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14304
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Have a MerCruiser 4.3 L alpha-1. I am totally vexed. Have

Customer Question

Have a MerCruiser 4.3 L alpha-1. I am totally vexed. Have fuel, spark, and compression. Cranks like a champ but wont start. Nothing.
Have 12.63v to coil, spark at coil to distributor wire, and spark plug wire, and spark at plug. Replaced, all six plugs. changed fuel filter twice. poured gas from filter into a jar, not seeing separation. compression checked all good. Totally vexed. Any ideas?
Submitted: 1 year ago.
Category: Boat
Customer: replied 1 year ago.
i have read the service manual and all the trouble shooting when you are getting fuel deals with no spark situations. Probably something unique to Mercruisers 4.3 Alpha One. Went over everything again with a very experienced marine mechanic this eve. So please no dumb answers that I have to get a refund for.
Customer: replied 1 year ago.
Compression read over 180
Customer: replied 1 year ago.
This is a link to the service manualhttp://boatinfo.no/lib/mercruiser/manuals/mercruiser32.html
Customer: replied 1 year ago.
Coil poll to poll was 0.8
Expert:  Jason replied 1 year ago.

Hello my name is ***** ***** am I speaking with?

There is a right and a wrong way to check for spark, how exactly are you checking it?

Do you have a timing light?

Will it run or at least hit on starting fluid?

Customer: replied 1 year ago.
Will not run on starting fluid. Qualified mechanic tested spark at plug, at plug wire, at distributor.
Expert:  Jason replied 1 year ago.

The engine needs 3 things to run.

Compression - Which you have

Fuel - At this point it would not matter if all of the gas in the fuel tank was water because starting fluid is a fuel. So even if the tank was full of water, or if there was no fuel hooked up to the engine, if there was a fuel problem it would run on starting fluid.

Timed spark ignition - This is what you are missing. There is either no spark, or, the spark is way out of time.

When did this problem start? Did the problem happen all of a sudden? Is there a story to this?

Also, you said mechanic, are you working on this yourself or is a mechanic telling you what he is doing?

Customer: replied 1 year ago.
Happened all of a sudden. Started first crank for @ 14 outings and last sat while in idle it quit. Doesn't usually do that. Would not restart Boat is 2007 but clean.I struck out DIY so brought it to a mechanic this eve and he used a spark tester. Test light. And clipped dust and plug wires w other end close to ground. And we got spark. starting fluid would eliminate fuel. Tested compression was excellent.
Been googling and seems others have experienced similar.
Customer: replied 1 year ago.
He pulled the distributor cap. No slipping so timing is unlikely?
Expert:  Jason replied 1 year ago.

Has a timing light been put on the engine?

Expert:  Jason replied 1 year ago.

Let me re=phrase that. What needs to happen is a timing light needs to get hooked up to the #1 cylinder. Somebody has to crank the engine over, while somebody else shoots the timing and see what it is reading. That is what needs to happen. Is that something you can do?

Customer: replied 1 year ago.
We can try that. We have tried everything else. But would bad timing happen so suddenly. Go from purring like a kitten to not starting at all, all of a sudden?
Customer: replied 1 year ago.
Considering he checked inside the distributor and everything was tight, no slipping, no cracks or carbon or signs of moisture or other problematic signs, Have you heard of timing going so bad so quick before?
Expert:  Jason replied 1 year ago.

Timing chains jump teeth, distributor gears shear off, there are a few things that can happen. Yes I have definitely seen things like this happen. And honestly until a timing light goes on the engine and you can see the flash, whether it has spark or not is questionable. There are no time limits here, do you want to that and check back in with me tomorrow?

Customer: replied 1 year ago.
I will try a new coil tomorrow. Even though everything tested well, from what I have read, some people had similar situation and evething tested well but new coil made it run.If that doesn't work first chance (probably next week) will check with a timing light(need to get one). These engines don't have points so skeptical but appreciate the suggestion. Worth checking since nothing I or my mechanic have tried so far has solved it. I will check back in next week.
Expert:  Jason replied 1 year ago.

Before buying a coil or spending any real money get a timing light first. If you have a place like an autozone near you they do free loaners on tools. Just pop a deposit down on a credit card, return the tool in working order and get your deposit back. There is no point throwing any money into guesses.

Customer: replied 1 year ago.
Can you refresh me on how to use a timing light? Haven't used one since I was a kid helping my dad time the station wagon 30+ years ago so I don't even remember the basics. . How do I identify the #1 cylinder.
Expert:  Jason replied 1 year ago.

#1 cylinder is front right. Hook up the timing light lead to that plug wire. Crank the engine over, and point the light at the timing tab just above the harmonic balancer and see where the line on the balancer lines up in relation to the timing tab. If everything is spot on.... It should be sitting at 8 degrees before top dead center, even when just cranking and not running.

Customer: replied 1 year ago.
The spec on this engine is 10 degrees btdc and it says special ignition timing required. Whatever that means.Can you explain how to find a timing tab and the harmonic balancer. Thought that was a part on the serpentine belt.
Customer: replied 1 year ago.
A metal part the belt goes around?
Expert:  Jason replied 1 year ago.

It's right near the bottom pulley. Just look down near the bottom center pulley, and you will see it.

If there Is anything else I will get to you tomorrow, i'm sigining off for the night. Good night!

Customer: replied 1 year ago.
I will google a video how to use a timing light. Thanks
Expert:  Jason replied 1 year ago.

You are most welcome.

Customer: replied 1 year ago.
While I'm still s bit skeptical of the cloud ( why will people store you data for free? Unless they are using it to make $) Gotta love the collective wisdom of the shared experience of other people.Turns out, and if anyone out there has a reliable Mercruiser (mine is 4.3L alpha 1 2007) that all of a sudden quits, cranks but won't start (real stumper), and the engine has spark and gas, put a new coil in it.Sierra replacement coil is less then $40 and will likely fix your problem.Mine started right up and purrs like a kitten again. Only two screws and one plug to connect (w/o bracket) to see if this solves it. Tons cheaper than any marine mechanical service.From now on I will be carrying an extra Sierra coil on my boat in case this should happen again.Thank heavens for those few who had the same experience and posted. Thank you. Thank you. Thank you.If anybody is a member of any boating sites please post this under MerCruiser engines "cranks but won't start.I hope that this will help others in the way that the post that I was able to find helped to me.2007 Mercruiser 4.3L alpha one. For this engine Sierra part # ***** OEM(###) ###-####4
Customer: replied 1 year ago.
Eric
Tallahasse Fl
Customer: replied 1 year ago.
Spent the last 4 days trouble shooting and even had a pro marine mechanic spend an evening on it. Finally found a post w similar before I tried the coil (because the coil resistance etc all checked out fine).
Expert:  Jason replied 1 year ago.

I'm glad to hear you got it Eric,

Happy boating!

Jason

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