Troubleshooting ignition coil 5.0 Mercruiser

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WrenchNhammer

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My boat starts and idles great but when I get up to 1200-1400rpm it it Boggs down. It’s a 2006 Mercruiser 5.0 MCM. I’ve sprayed a mist of fuel into carburetor intake and nothing happens so I’m thinking it’s in the ignition system. I’ve put new plugs/wires cap and rotor. Looking at the coil, I have 12v with key on. 13.7 while at idle on both the wires. Is this coil externally resisted?
 
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WrenchNhammer

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Isn’t one of the 2 wires supposed to be negative? Neither shows (-) when I tested with one test lead on either side and the other on ground stud
 
alldodge

alldodge

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WrenchNhammer said:
Isn’t one of the 2 wires supposed to be negative? Neither shows (-) when I tested with one test lead on either side and the other on ground stud
Click to expand...
No, the negative side is switched to ground by the distributor. You have a TBV ignition. Run through this guide to see what is wrong

TBV Troubleshooting.jpg
 
Bt Doctur

Bt Doctur

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according to your serial number you are a MPI motor . There is no carb on it.
Best guess is the fuel pump is not producing a constant 41 psi. Test the fuel pressure first
 
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WrenchNhammer

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I’ve already replaced the ignition sensor as well… as well as new water/fuel separator. The hard fuel line had a slight bend in it so NEW. Replaced w/OEM fuel pump checked to inline filter again. Took top off carb and checked for debris
 
Scott Danforth

Scott Danforth

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its not your coil

its almost never the coil and the fact that your engine is running proves its not the coil.

what is your fuel pressure?
how did you "check" the fuel filter? they are a one-time use filter
 
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WrenchNhammer

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I was referring to the small mesh filter in the inlet to the carb. The element was replaced at the beginning of the season
 
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WrenchNhammer

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Funny story about fuel pressure, after I installed the new electric fuel pump, I got one of those rental fuel pressure test kits but it was defective and sprayed fuel at me out the pressure relief. That’s when I took it to the shop where it sat for 3-1/2 weeks. I called another shop that told me they could start on it Monday so I drove almost an hour to get it there,just to be told they won’t be able to start on it for a month or so
 
Scott Danforth

Scott Danforth

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WrenchNhammer said:
I was referring to the small mesh filter in the inlet to the carb. The element was replaced at the beginning of the season
Click to expand...
what about the water-separating filter?
you still need to test fuel pressure and you need the special fitting to do so.
 
Bt Doctur

Bt Doctur

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Damm , dyslexkia sucks, cant type those numers correctly .your correct on the TKS 5.0
Try using a remote tank to eliminate the fuel system.If you run good on the remote and you have checked the anti-syphon There may be another filter to remove.
 
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