Mercruiser 260 died won't start

[pmjr0987]

Hey guys so I have got about 10 hours on the boat since I bought it and it has run 100% every time except some high rpm restrictions limiting the motor to about 4,000rpm. Runs hard to than till it just stops accelerating. I'm getting about 45 mph out of 4,000 rpm on a 19p prop which I see on here is pretty good


Fast forward to last Sunday I run it trying to beat the rain at about 3700 rpm (about 43mpg on GPS) and make it to the marina I get my truck and come back and the engine stalled. Will NOT start at all.

I smell fuel so I think that's OK

I check the voltage at the coil and I'm getting 5 volts after the ignition ballist. Before that part im seeing 11 volts and my battery is a little over 12 volts.

I'm not getting any spark and I tried swapping out the coil (new two months ago Sierra model) with the old one that I replaced just to replace it as a tune up. Same problem. I put a screw driver in the coils wire and I get no spark to ground.

The boat as a Mallory distributor says its magnetic electric and has three wires coming out and all look ok. All the wires look fine no fraying.

The motor (and boat) is a 1985 mercruiser 260 5.7 v8 model

When I'm cranking the boat the voltage at the + side of the coil to ground is less than 4 volts

 

[alldodge]

Have a look here and see if this will help troubleshoot it
http://www.msdignition.com/page.aspx?id=3206

 

[pmjr0987]

Thanks, I don't have that msd box though I have the distributor, and coil. I believe it's all self contained without that box.

I'm reading some places say I should have 6 volts on the + coil when ignition on and some say 12 volts. Either way both say it should be full voltage when cranking and I'm seeing just 3-4 volts while cranking at the coil. Is this normal? After i figure out what voltage that coil should be reading I could tap into that white wire to ground it out and see if the coil fires

 

[alldodge]

3-4 volts while cranking at the coil. Is this normal?

Electronic ignition should see a full 12V starting and running. Only ones which should see less in the 9V range is points. You don't have points so it really needs to be higher then 3 to 4V

 

[pmjr0987]

Ok my boat has an ignition ballist on it located on the left riser. Before that it's a little over 11 volts, after that it's the 4-5 volts. I jumped the wires to the coil and still didn't get spark from coil trying to crank

 

[pmjr0987]

No Title

Also can anyone help me figure out what model # distributor I have from Mallory I'm attaching a photo here but I can't make out the #'s stamped in it

 

[alldodge]

after that it's the 4-5 volts

That's still a bit low. The Sierra coil you swapped out was one which called for external resistance?
There are up to two wires on the Negative (-) side of the coil. One goes to the distributer, the other goes to the tach. Remove both wires, attach a jumper to the (-) terminal, remove coil wire from distributer and hold it near a ground (not on the ground). Just briefly touch the jumper on the (-) side of the coil to ground and see if you get a spark, you should

 

[pmjr0987]

Ok thanks I will try that procedure. I do have three wires to the negative side of coil not sure why .

I'm attaching a link to the coil I purchased

 

[alldodge]

The sierra coil you have (18-5438) is for electronic ignition and does not use an external resistor, you need 18-5433 which uses an external resistor. That is it your Mallory distributer requires an external resistor.

 

[pmjr0987]

Very interesting thanks for that help. On amazons website the model you are referring to says its for efi motors. And older 1970 era motors.

Question though, why would the motor run so well the past 5-6 times out? Started immediately planed off well good mpg than all of a sudden die?

Also when I swapped in the old coil it still didn't have spark.

Either way thanks for your help. I will order this coil tomorrow and amazon will have it to my door Monday

 

[alldodge]

I'm not saying buy the other coil, what I'm saying is the one you have is used without a resistor (normally). Where we could be having the trouble is exactly what kind of ignition distributer you have. You might have a ignition module breaking down, not enough voltage, or something else. Without knowing which system, I'm guessing as to how to troubleshoot.

As far as running good then die, it could be as simple as the coil breaking down or the module

 

[pmjr0987]

Ok I do understand its all guessing till I figure out what model distributor ci have. Why Mallory stamped the numbers on that plate in a way I cant read is crazy if u ask me lol.

Reading up I see some Mallory units need coils that have at least 1.4 ohm resistance. I see my coil online should be around .8-.9 ohm which you are correct is out of spec.

The unit you referenced says its about 1.2 ohms.

There are Sierra units that have 1.5 ohm (says high performance) but idk of it uses an external resitor like Mallory says their distributor needs.

In iboats if you look up my engine it shows my 5438 model as the correct unit for my engine. So I guess they (whoever did the modification) added the resistor when they swapped in the Mallory distributor. And that inturn makes me need a different coil than what's recommended with a factory setup ... Still learning but its kind of making sense

 

[harleyman1975]

They used those ballast resistors in mopars for many years and I have changed my share. it is cheap to do so I would start there also make sure you have 12 volts plus from your battery when it is sitting.

 

[pmjr0987]

The sierra coil you have (18-5438) is for electronic ignition and does not use an external resistor, you need 18-5433 which uses an external resistor. That is it your Mallory distributer requires an external resistor.

I took the coil off and right on it it states "use with external resitor" it says that it's required if used with non thunderbolt ignition. It's a sticker on the coil. I wonder why they would put that on this coil. Does that mean it should work with my distributor?

 

[alldodge]

Does that mean it should work with my distributor?

Again I don't know, and the main reason why is I don't know which Mallory distributer and module you have.

 

[pmjr0987]

Yea I understand. On post 6 I uploaded a photo of the distributors model number, but I suppose it's old and the numbers are faded. I can't read them for the life of me, but the distributor does look like the unilite distributor they have on there website. It also has the three (red, green, brown) wires that the new unilite has as well.

 

[alldodge]

The first pick is for what you should be wired to, the second is if you have a coil with internal resistance.
http://prestoliteperformance.com/me...tructions_unilite_distributor_37_38_45_47.pdf






Here is the test procedure and the type of coil which should be used.

What is the Test procedure for checking my Unilite electronic ignition module?s operation? A: INSTRUCTIONS

• Remove both the distributor cap and rotor, then turn the ignition ON but DO NOT START car.
• Now connect your Red voltmeter wire to the NEGATIVE terminal (-) on the coil, by attaching the Red lead wire clip from voltmeter to the (-) terminal.
• Next attach your Black voltmeter wire to an engine ground on a good ground source. We suggest a manifold, or header bolt. Most anywhere on the engine is good.
• Now the voltage should read about 11 to 12 volts at this point. Remember to turn the key on for this reading! 12 volts must be present on your voltmeter.
• Next, place a credit card down into the distributor, blocking the 2 photo optic eyes on top the module facing each other on the top. With eyes blocked, the volts should drop way down below 2 volts or less. This drop is a must! If the voltage drops down to anything under 2 volts, then the module is good and ready to use. If the voltage does NOT drop, the module will need to be replaced.
• This damage could have been caused by many things, such as: power surge from an alternator, high resistance spark plugs and plug wires, improper ground wires, if someone has given you a jump, if you have given someone a jump, or battery chargers, which can also damage ignition modules. If voltage always stays below 2 volts and never increases up to 11-12 volts, then the module has been spiked by high voltage and needs to be replaced.

NOTE: The lack of a ballast resistor will cause this type of spike. If the voltage only drops down to 3-4 volts, this will produce a weak spark: too weak to run engine and the module will need to be replaced.

What coil should I use for my Mallory Unilite distributor, and/or Mallory Hyfire CD ignition box?

A: All Unilite distributors need coils with a minimum amount of 1.4 Ohms primary resistance. Coils are 12 volts; however, they do have different amounts of primary resistance, which is measured in Ohms. You can still use a coil with less than 1.4 Ohms, but you must install a Ballast Resistor (Mallory #700) between the coil and the distributor, install on Red wire coming out of the Unilite distributor. It is Important to know that the Unilite distributor will work initially on the engine with less than 1.4 Ohm, BUT NOT FOR LONG. It only takes a short period of time to burn up the module using a coil with the wrong resistance.
When you select a coil for any High power CD ignition box like the Mallory Hyfire CD boxes, the Mallory Hyfire CD boxes MUST always use a coil with LESS than 1 Ohm of primary resistance.

 

[pmjr0987]

I am getting less than 2 volts on the coil (positive lead from tester on negative coil, ground from tester on ground. Blocking anything in the distributor does not change anything. Voltage to the + side of coil is about 5 volts, and before the balast resistor is nearly 12 volts. Battery is reading about 12.5 volts at its polls.

 

[pmjr0987]

No Title

Here's a photo of the distributor if anyone can identify it the stamped #'s on the side are basically mushed flat and can't read

I'm wondering if the ballast is bad now. Is it doing what its supposed to and lowering the voltage, or in just ignition on without the motor running is it supposed to jack up the voltage for starting

 

[alldodge]

I am getting less than 2 volts on the coil (positive lead from tester on negative coil, ground from tester on ground. Blocking anything in the distributor does not change anything. Voltage to the + side of coil is about 5 volts, and before the balast resistor is nearly 12 volts. Battery is reading about 12.5 volts at its polls.

What happened when you ran through the test above? The test above indicates the voltage should drop below 2V

place a credit card down into the distributor, blocking the 2 photo optic eyes on top the module facing each other on the top. With eyes blocked, the volts should drop way down below 2 volts or less. This drop is a must! If the voltage drops down to anything under 2 volts, then the module is good and ready to use. If the voltage does NOT drop, the module will need to be replaced.