Mercrusier 4.3-1993 coil

[kulle]

Hello- still troubleshooting and getting nowhere. I’m trying to determine if my coil is or is going bad. On the lake I had a few instances where under 3/4- full throttle the boat sputters and stalled. Got it started right away but stalled a little later then would not start. Someone told
me that sounds like a possible bad coil. So I tested my coil readings -
Specs for this are- pri .6-.8 and sec 9.4k -11.7k
my readings
cold
pri- .9
sec- 10.2k

after idle and some throttle to 3k rpms(I could not get it to stall)

pri- 1.3
sec-11.4k

are those increases normal - just had oil pressure switch replaced as I could not keep boat running for more than 30 secs. Appreciate any expertise to hopefully save me another $500

 

[Scott Danforth]

its almost never the coil.....ever. like seriously ever. only about 3 out of a million changed coils are bad. most people change them because they dont do the troubleshooting.

your resistance values are fine.

go thru the thunderbolt IV trouble shooting. higher probability its the ignition module

 

[kulle]

i did review that ign troubleshooting, i have spark at dist and to spark plugs. so not sure where to start in that flow chart.

 

[Bondo]

i have spark at dist and to spark plugs.

Ayuh,..... Then the coil is Firin',.....

 

[kulle]

i'm following http://www.boatfix.com/merc/Bullet/92/92_11.pdf

and i grounded the coil HT with spark gap tester in line, pulled the gr/wh lead that goes into distributor and with key in "run", struck it to ground and did NOT get spark, so the guide tells me to replace coil, so i ordered one.

 

[Bondo]

i have spark at dist and to spark plugs.

Ayuh,.... You said ya got spark at the plugs, 'n distributor,......

Just where do you think the spark is comin' from when it's gettin' to the spark plugs,....

 

[Fun Times]

i'm following http://www.boatfix.com/merc/Bullet/92/92_11.pdf

and i grounded the coil HT with spark gap tester in line, pulled the gr/wh lead that goes into distributor and with key in "run", struck it to ground and did NOT get spark, so the guide tells me to replace coil, so i ordered one.

Just to let you know that older test is sort of incomplete...There are two important missing steps and the testing process of the green/white wire needs proper action as the wire needs to be stuck rapidly such as 2 - 3 + times a second to help simulate a running engine or you may get a false read.


https://forums.iboats.com/forum/eng...underbolt-ignition-test?p=5414151#post5414151

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[Scott Danforth]

i did review that ign troubleshooting, i have spark at dist and to spark plugs. so not sure where to start in that flow chart.

if you have spark.... you do not have a coil issue.

 

[kulle]

yeah i figured but am getting desperate, so purchased one anyway, current one looks old. so if i got spark, what is best way to rule out ign sensor or icm? or could dirty dist cap/contacts cause the issue...wondering why mechanic didnt check this stuff.

 

[Scott Danforth]

or could dirty dist cap/contacts cause the issue...wondering why mechanic didnt check this stuff.

yes......

 

[kulle]

Just to let you know that older test is sort of incomplete...There are two important missing steps and the testing process of the green/white wire needs proper action as the wire needs to be stuck rapidly such as 2 - 3 + times a second to help simulate a running engine or you may get a false read.


https://forums.iboats.com/forum/eng...underbolt-ignition-test?p=5414151#post5414151

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So I must not be doing something right...I bought a new coil and performed the test. I removed the HT lead from Dist cap. I connected that end to battery ground, so the Coil is grounded. ( I left both grey wires on coil neg and both purple wires on coil pos). I unplugged the gr/wh wire from distributor and with key on run, rapidly struck the ground where the neg wire of the distributor sensor goes, did not get a spark on my spark gap tester which is inline with coil. I have a new dist sensor coming too, going to start replacing stuff- very frustrated. Thanks all for the knowledge !

 

[kulle]

So 4 months after getting this used POS, 1993 Sea Ray 180 BR ( 4.3 merc 2bbl carb) it still isn't running right. To date have replaced/tested:
-oil pressure switch-replaced
-fuel/water seperator-replaced/checked
-ign coil / distributor sensor - replaced
-tested for spark
-checked fuel vent line
-have good battery and groundconnections
-checked carb inlet screen
-put can of sea foam in 1/2 tank of gas
-replaced rotor( cause i broke it removing it to clean/check dist cap)
-ruled out issues with neutral safety switch grounding out while underway ( simply unplugged it)

The boat runs fine out of water in a tub in idle and small load. When I get it onto lake, the last time after replacing some of these items, ran good, only shut off twice but restarted each time and i didnt need a tow. Had it out this past weekend and it shut off not soon as we got outside the no wake area and continued to shut off, restarted a few times right away, then it wouldnt. Luckily was close to docks, just paddled. fuel pump issue? bad gas? Im about ready to sell it and just take a loss. running out of ideas. Please help ?!

 

[Scott06]

When it shuts off do you have spark ? And do you have gas in the carb ? Can check gas by pumping the throttle and seeing if you get good gas stream out of the accelerator pump

did you check the ignition timing and advance curve

 

[greno]

How long was this boat setting before you bought it?
You may just have a fuel issue. If the previous owner ran ethanol in it and then let it sit for a while the ethanol is water-affilic. It will attract water out of the atmosphere and that can do things like corrode fuel tanks, fuel lines, etc. Ethanol itself will attack certain gaskets, seals and fuel hoses. Try running the boat attached to a small fuel can with fresh marine fuel and see if it affects the problem.

 

[AShipShow]

Have you rebuilt the carb?

 

[kulle]

When it shuts off do you have spark ? And do you have gas in the carb ? Can check gas by pumping the throttle and seeing if you get good gas stream out of the accelerator pump

did you check the ignition timing and advance curve

I'm pretty sure i have spark or at least most of the time , since it starts back up. just now and then it wont. Can I test any plug for spark coming off dist cap next time it wont start? Last I checked giving throttle shot gas into carb. I am not sure how to check/change ignitaion timing, not sure i have the tools.

 

[kulle]

How long was this boat setting before you bought it?
You may just have a fuel issue. If the previous owner ran ethanol in it and then let it sit for a while the ethanol is water-affilic. It will attract water out of the atmosphere and that can do things like corrode fuel tanks, fuel lines, etc. Ethanol itself will attack certain gaskets, seals and fuel hoses. Try running the boat attached to a small fuel can with fresh marine fuel and see if it affects the problem.

I don;t know how long it was sitting, im going to think not too long, a season maybe? Thing is, it runs good when i fire it up on muffs or drop engine in bin of water and give it throttle. I did not mess with the carb other than check a ffew tings i could see and spray it with carb cleaner. When I got the boat it had a FULL tank. The first time out when it ran great, we ran about 1/2 tank, then I topped off with normal 87 octane from a local sheetz. issues with shutoff ironically started that run, but not sure if i can tie it directly to gas or the fact that I ran it good the previous run and wore or broke something.

 

[greno]

After ruining one carb and two fuel tanks running ethanol I quickly realized there was no savings there. These older boats and systems just weren't designed to handle the newer ethanol fuels. I run strictly non-ethanol marine fuel in all our boats.
Just one less headache to deal with.

 

[Bondo]

Thing is, it runs good when i fire it up on muffs or drop engine in bin of water and give it throttle.

Ayuh,..... You should Always use the muffs,.....

Donno how much you've run it with the drive in a tub, but I can pretty much guarantee ya now need a new impeller in the drive,....
The drive needs to be submerged,.....
If only to the water pick-up holes, the impeller runs dry, as it's a flooded entry pump,.....

 

[greno]

Bondo, I was hoping he was doing this: