Dual plug land and sea 2.4 heads

**62 bugzilla** · 09-25-2023, 03:33 PM

I saw a set of these are they a gimmick or tru performace add on?

**David - WI** · 09-25-2023, 03:52 PM

L&S has been out of the performance boat market (other than their dynos) for probably 20 years.

I have a couple sets of their heads billet single-plug, billet dual-plug, cast dual-plug. I think they can make power but only in combination with other mods and serious tuning changes.

**Jim Speros** · 09-25-2023, 04:57 PM

Land and Sea was a long time ago. They did create a 500 hp 2.4 turbo. That engine probably appreciated dual plug heads.

I remember hearing a story that turbo engine burned down Dick O Dea's dyno. They wound it up and could not shut it down. It was assumed it was drawing air in past plenum gasket and leaned out.

**Mrzip** · 09-25-2023, 05:15 PM

Dick O Dea'. I had a 2.4 200 he did many years ago. I he still with us ?

**wolfgangb** · 09-26-2023, 09:57 AM

Originally Posted by David - WI

L&S has been out of the performance boat market (other than their dynos) for probably 20 years.

I have a couple sets of their heads billet single-plug, billet dual-plug, cast dual-plug. I think they can make power but only in combination with other mods and serious tuning changes.

I have a set of L&S billet dual plug heads, which I would love to put on my 2.5 ROS motor. Question is; how do I reliably fire the dual plugs? Would for instance a dual plug wire coil say from a Ficht motor be compatible with the Merc control box(s)?
Any help would be most appreciated.
Wolfgang (South Africa)

**David - WI** · 09-26-2023, 10:15 AM

I was planning to use the MegaSquirt EFI... which can fire (12) of the GM/Merc "smart" coils directly.
https://www.diyautotune.com/product/ign-1a-race-coil/

**wogi** · 09-26-2023, 11:45 AM

Originally Posted by 62 bugzilla

I saw a set of these are they a gimmick or tru performace add on?

There is a set on feebay, i was told by a guy on here that they run hotter due to reduced water flow through them

**patchesII** · 10-02-2023, 08:03 PM

I wouldn’t use them. Water flow was terrible. Factory Mercury heads and chamber architecture is quite good, I’d stick with them

**David - WI** · 10-03-2023, 10:34 AM

Like I said, you kind of have to rethink your whole tuning strategy or you‘ll have nothing but trouble... dual-plug heads require a lot less ignition advance to make more power, for one thing.
Arctic Cat had dual-plug snowmobiles back in the mid-70‘s that were very hi-pert for the time, but a lot of people struggled to make them work.

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**25two.stroke** · 10-03-2023, 12:04 PM

Originally Posted by David - WI

Like I said, you kind of have to rethink your whole tuning strategy or you‘ll have nothing but trouble... dual-plug heads require a lot less ignition advance to make more power, for one thing.

That ad is a badass piece of history. I want a printout. I have a set of those for mercury, same color dual plug. In your experience what would you set a motor at for starters running the dual plug heads? 20? Is that a safe starting point?

**wogi** · 10-03-2023, 01:01 PM

The ones on Feebay, the seller offered me a $25 discount just because I clicked on and looked at them, didn't even add them to my watch list.

**David - WI** · 10-03-2023, 01:11 PM

I haven't run them. I bought them for a 260 that'll still sitting in boxes. I was going to start at 5* and work up... I would be shocked if they need/allow 10* of advance.

I've talked to several guys that ran them, but nobody would share the secret number!

**25two.stroke** · 10-03-2023, 01:48 PM

Originally Posted by David - WI

I haven't run them. I bought them for a 260 that'll still sitting in boxes. I was going to start at 5* and work up... I would be shocked if they need/allow 10* of advance.

I've talked to several guys that ran them, but nobody would share the secret number!

Dammit. Yeah I have a set they are so pretty I've been afraid to bolt em on. I was gonna run them off the basic switchboxes with dual coil leads going up. I head the switchboxes could run 2 sets of coils...so I'm gonna try it. I'll probably run into weird problems at high rpm????

**David - WI** · 10-03-2023, 03:29 PM

I think that's how they normally ran. I'll see if I have any paperwork next time I'm at my storage building.

I bought 12 GM LS "smart" coils before I found out about the IGN1a coils I posted above.

I think most of the people that had problems had way too much advance. With two ignition points the pressure rises much faster, so you have to light it much later in order for it to peak when it needs to.