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Old 07-21-2019, 07:47 AM
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95 336 with 525SC's

port motor has had intermittent issues last year, this year started in driveway, then was very difficult to start at ramp, crank crank crank then all of a sudden fired.
went for a ride, back off plane and idle and after a while stalled, crank crank forever, occassional fire, finally started and ran rough at throttle, then would quit at idle

replaced cap, rotor, hei sensor, coil, thunderbolt, and rebuilt carbs. cranked with occassional fire, and now just cranks.

getting plenty of fuel.

could it be voltage drop may have someting to do with it???
cranks and holds about 10V during crank at helm meter.
is there some ignition relay somewhere? a buddy just mentioned he had this on his formula (98). cranked but would not start.

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Old 07-21-2019, 11:07 AM
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do U have voltage at coil with key on and also while cranking? Use a test light.
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Old 07-21-2019, 01:35 PM
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12v with ignition on. Need to check voltage while cranking next.
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Old 07-22-2019, 05:48 PM
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If it's 10v at helm during cranking I would guess low voltage at the motor ... can you start with both batteries? Pick up one of the load testers from Harbor Freight to test the battery ...m
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Old 07-22-2019, 07:05 PM
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ordered a spark gap tester, shoudl come in a few days.
Will verify spark whiel cranking
can also check battery load condition.
I usuallty always run both batts as the blow motors take a lot to turn over.
they are both two years old but I forgot to flip the shore power switch over the winter and they sat (isolated) in my cold polebarn.
but I had some trouble last year with this engine randomly stalling at idle, and occassionally under very rough seas ( launching) it woudl quit and come back on.
may verify tach lead is not the issue as I read that can cause issues.
will also put a volt meter on the coil during load, but I guess spark tester will be an even better test
after that I am seeking professional help (psychologist and mechanic)

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Old 07-22-2019, 07:07 PM
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also.. neither engine will start while cranking, need to release from "Start" mode to run and they fire, jsut seems like a voltage, or voltage relay issue?
I read somehwere that there is a separate relay for when cranking then a lead (with resistor?) for on.. not sure if my gen has that or not.......?????
and if so, where it is
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Old 07-22-2019, 10:38 PM
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How long have you had this boat and how long these issues ? Any repairs right before this release cranking and it starts issue ? This is usually low voltage to coil during cranking, but good voltage to coil when not cranking issue.
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Old 07-23-2019, 08:08 AM
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10 yrs
last 2 or 3 years have noticed the key issue
replaced keys two years ago but still present
replaced batteries two years ago.
seems I need to measure voltage at coil, and if too low, then determine root cause: batteries, or big cables, or small wires.......
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Old 07-23-2019, 09:52 AM
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Maybe you have already done this and I didn't read it. Have you removed the ground leads from the back of the engines and cleaned them well? This all sounds like a voltage issue.
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Old 08-13-2019, 10:18 AM
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found the root cause
rev limiter under the thunderbolt ignition
problem is the part is obsolete, no replaccement and the marine repair facility cannot locate a part
any suggestions?
is the part used on other blue motors?
what is the best alternative?
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