Merc 496 HO Spark Plugs

[Cobalt272!]

Planning to do my plugs in Spring. Tons of different info and perspectives on running the recommended AC 41-983 plugs vs the NGKs. I'm leaning towards NGK. They offer the Iridium series (TR55iX) or Laser Platinum pztr5a-15.

Any insight, thoughts or experience would be appreciated w/r/t performance, fuel consumption, longevity.

[Big Block Power]

Myself I always run what the factory puts in it. Normal AC plugs will last you years in a boat. Everytime I don't put the factory ones in it, it never runs the same. That's my 10 cents.

[cmattj]

Planning to do my plugs in Spring. Tons of different info and perspectives on running the recommended AC 41-983 plugs vs the NGKs. I'm leaning towards NGK. They offer the Iridium series (TR55iX) or Laser Platinum pztr5a-15.

Any insight, thoughts or experience would be appreciated w/r/t performance, fuel consumption, longevity.

As BB said AC is the correct plug. Do you do any oil mix winterizing? If yes just stay with AC and do them yearly.
Most 496ho are just pump the air out? So your plugs will last a long time.
So..
AC 41-983 are the OE platinum.
AC 41-993 are their iridium design, Like the NGK TR.

Running a plug that doesn’t shield emf etc can be a problem as you’ve noticed your ecm is right on top and don’t like plugs and wires that emit non suppressed spark energy fields.

Stay with either (41-983 or TR55ix) but carful on gapping as to never use a pull through gapper. Just one that grabs the edge.
They should be already at .060 but .050 is fine.

Now remember to give us a performance report!

[Lockey14s]

Planning to do my plugs in Spring. Tons of different info and perspectives on running the recommended AC 41-983 plugs vs the NGKs. I'm leaning towards NGK. They offer the Iridium series (TR55iX) or Laser Platinum pztr5a-15.

Any insight, thoughts or experience would be appreciated w/r/t performance, fuel consumption, longevity.

As BB said AC is the correct plug. Do you do any oil mix winterizing? If yes just stay with AC and do them yearly.
Most 496ho are just pump the air out? So your plugs will last a long time.
So..
AC 41-983 are the OE platinum.
AC 41-993 are their iridium design, Like the NGK TR.

Running a plug that doesn’t shield emf etc can be a problem as you’ve noticed your ecm is right on top and don’t like plugs and wires that emit non suppressed spark energy fields.

Stay with either (41-983 or TR55ix) but carful on gapping as to never use a pull through gapper. Just one that grabs the edge.
They should be already at .060 but .050 is fine.

Now remember to give us a performance report!

Is this the same case for Volvo 8.1?

[cmattj]

Is this the same case for Volvo 8.1?

You betcha..... even though Volvo seems to use a proprietary number.. Fancy Swedes right?
The ecms are a different style, and design (mefi) and on the opposite side of the engine but still on top. Stay with a Platinum replacement.

[Lockey14s]

Is this the same case for Volvo 8.1?

You betcha..... even though Volvo seems to use a proprietary number.. Fancy Swedes right?
The ecms are a different style, and design (mefi) and on the opposite side of the engine but still on top. Stay with a Platinum replacement.

Good to know, thanks for the info. I have heard that also, that they dont like the iridium plugs

[Cobalt272!]

Great stuff, thank you. I'll be sure to stick with the AC 41-983 Iridium. And yes, I do a full winterization with oil mixture.

[AsLan7]

Planning to do my plugs in Spring. Tons of different info and perspectives on running the recommended AC 41-983 plugs vs the NGKs. I'm leaning towards NGK. They offer the Iridium series (TR55iX) or Laser Platinum pztr5a-15.

Any insight, thoughts or experience would be appreciated w/r/t performance, fuel consumption, longevity.

.
We just installed new iridium plugs in ours a couple of months ago C272!. Picture here.

Be sure to gap at .060" as the Merc 496 manual recomends.
.

[Lockey14s]

Planning to do my plugs in Spring. Tons of different info and perspectives on running the recommended AC 41-983 plugs vs the NGKs. I'm leaning towards NGK. They offer the Iridium series (TR55iX) or Laser Platinum pztr5a-15.

Any insight, thoughts or experience would be appreciated w/r/t performance, fuel consumption, longevity.

.
We just installed new iridium plugs in ours a couple of months ago C272!. Picture here.

Be sure to gap at .060" as the Merc 496 manual recomends.
.

Runs well with the iridium plugs?

[AsLan7]

It does!
Ran the last iridium plugs for two years.

[Big Block Power]

So I pulled a plug today. It looked great. But I looked at the electrode and it just looked weird. The angle wasn't right. So doing some searching I think it has the wrong plugs in it. I think it wanted too be a small block in its after life. It has mr43lts plugs in it.from what I can find they fit the small block.
From all the searching of should have the double platinum or DP for short
Volvo part number 3861326 Mercury part number
33-863622001
or NGK PZTR5A-15 or
AC Delco 41-983
Or Denzo TJ14R-P15
And gapped to. 060

[AsLan7]

So I pulled a plug today. It looked great. But I looked at the electrode and it just looked weird. The angle wasn't right. So doing some searching I think it has the wrong plugs in it. I think it wanted too be a small block in its after life. It has mr43lts plugs in it.from what I can find they fit the small block.
From all the searching of should have the double platinum or DP for short
Volvo part number 3861326 Mercury part number
33-863622001
or NGK PZTR5A-15 or
AC Delco 41-983
Or Denzo TJ14R-P15
And gapped to. 060

.
How weird?
Remember this....

.

[Big Block Power]

So I pulled a plug today. It looked great. But I looked at the electrode and it just looked weird. The angle wasn't right. So doing some searching I think it has the wrong plugs in it. I think it wanted too be a small block in its after life. It has mr43lts plugs in it.from what I can find they fit the small block.
From all the searching of should have the double platinum or DP for short
Volvo part number 3861326 Mercury part number
33-863622001
or NGK PZTR5A-15 or
AC Delco 41-983
Or Denzo TJ14R-P15
And gapped to. 060

.
How weird?
Remember this....

.

That was your misfire? Mine didn't look like that. Just like it comes with a .060 gap and it was changed to .042 it was bent by a human. And it just didn't look right. Glad it didn't look like that one. Whew.

[AsLan7]

Our misfire was a bad number 3 coil pack
We have no idea how this plug got this way. Weird.

[Big Block Power]

Our misfire was a bad number 3 coil pack
We have no idea how this plug got this way. Weird.

Definitely. I wish I knew why the PO had these plugs installed? I just wonder what was in it first.