300xs spark plugs diagnose coil issue

[John2250]

Hey everyone so I have a few questions, I have a 2007 300xs, has all the updated coils in it they were replaced back in 2010, but the boat is forsure down on power it struggles to plain out on a 24p bravo 1, that being said compression is all good, all injectors we’re just cleaned and given a clean bill of health, I just swapped these plugs they have one trip maybe 2 hours on them tops take a look and see what you guys think, also let me say I think from looking at the plugs it needs 2-3 coils should I replace all 6 or can o just swap what I think is bad?

[davemvegas]

A DDT or Rinda will fire coils to test spark. Without a tool you can check coils the shade tree way with a successful outcome. Unplug fuel pump at connection just below VST. remove one plug wire at a time from coil, not spark plug.use medium size screw driver to check spark. push screwdriver firmly against head bolt or any metal part of block for grond. angle blade toward coil tower. holding at approx 1/2 inch gap. crank motor over a few seconds. If you get blue lightning bolt. Coil is good. If you get orange or no spark. Coil is bad. PS. Keep your hand on insulated screwdriver handle. Touch blade of screwdriver while motor is cranking over. Will make run out of sight to see if your nuts are still intact after smoke clears.

[John2250]

A DDT or Rinda will fire coils to test spark. Without a tool you can check coils the shade tree way with a successful outcome. Unplug fuel pump at connection just below VST. remove one plug wire at a time from coil, not spark plug.use medium size screw driver to check spark. push screwdriver firmly against head bolt or any metal part of block for grond. angle blade toward coil tower. holding at approx 1/2 inch gap. crank motor over a few seconds. If you get blue lightning bolt. Coil is good. If you get orange or no spark. Coil is bad. PS. Keep your hand on insulated screwdriver handle. Touch blade of screwdriver while motor is cranking over. Will make run out of sight to see if your nuts are still intact after smoke clears.

haha okay I’ll give that a try thanks !

[John2250]

A DDT or Rinda will fire coils to test spark. Without a tool you can check coils the shade tree way with a successful outcome. Unplug fuel pump at connection just below VST. remove one plug wire at a time from coil, not spark plug.use medium size screw driver to check spark. push screwdriver firmly against head bolt or any metal part of block for grond. angle blade toward coil tower. holding at approx 1/2 inch gap. crank motor over a few seconds. If you get blue lightning bolt. Coil is good. If you get orange or no spark. Coil is bad. PS. Keep your hand on insulated screwdriver handle. Touch blade of screwdriver while motor is cranking over. Will make run out of sight to see if your nuts are still intact after smoke clears.

Whats your opinion on just replacing the bad ones ?

[davemvegas]

I have the the same trust with any good working electronic part. As i have with a new untested part I would only replace a weak coil. If spark is good i would reuse.

[John2250]

I have the the same trust with any good working electronic part. As i have with a new untested part I would only replace a weak coil. If spark is good i would reuse.

Sounds good thank you !

[rocketman6965]

Only one plug looks right there. 4th one from the left. I know I'm going to get flack from some members here but make sure they are gapped to .044. Do not gap conventional way by inserting gap tool between electrode. I use a needle nose to move s to not make contact with precious metal then use the "no go, go" method with gap tool.

[davemvegas]

If you do not find a bad coil or two. May have leak in one of the diaphrams on fuel rail. while idling push in valve core on air rail. There may be a very light mist of water from condensation. But if there is any fuel smell at all. Change diaphram.

[Euroski]

I have 3 300xs coils listed for sale at $75 each if interested?

[jbutah]

Could also be the coil wire harness. I had coils dropping out intermittently and a new wire harness is what fixed it.

[Jamie Nichols]

Why are those plugs so black looking?

[John2250]

If you do not find a bad coil or two. May have leak in one of the diaphrams on fuel rail. while idling push in valve core on air rail. There may be a very light mist of water from condensation. But if there is any fuel smell at all. Change diaphram.

So I tripled checked all my coils they all pass the spark test, today I pulled my tracker valve and found it pretty much torn in half and I was getting a pretty good fuel mist from the air side valve

[rocketman6965]

That'll do it.

[John2250]

That'll do it.

I swapped it out and it forsure runs way better I feel like it’s maybe not quite right, I’m debating on serving the other 2 Diaphrams

[rocketman6965]

Other two? You have a fuel regulator on the other rail. Need special tools for that one.