Spark plugs for Merc 8.1 Horizon

DDD

DDD

New Member
Oct 27, 2012
268
Tampa, FL
Boat Info
2008 45
Engines
Diesel
Just read the maintenance on the Mercruiser 8.1 Horizon.
Recommend changing spark plugs every 300 hrs (I am not there), or 3 years (I'm at 5).

Any input on the importance of this?
Should I go ahead and change them?

Any recommendations on the type?
Any give you increased performance?


Thanks!
 
DDD
What is the plug make/model on you motor currently?
 
Given that his boat is a 2008 and he indicates that his plugs are 5 years old it is safe to assume that he has the plugs that came from Mercruiser. His first question is whether he really needs to change them with under 300 hours on them.

His second question interests me as well. If I go onto one of the BMW or Lexus forums and ask a similar question I would expect a raucous debate on various brands and styles. NGK versus Bosch, Platinum versus Iridium, one electrode versus four, etc. Can marine engines benefit from any of the ostensibly advanced spark plug technologies or are the standard plugs all that they need? (For what it is worth I ended up with Bosch Platinum +4 for my wife's Z4 lol)
 
Here's my view; the 8.1/496 engine is derived from a truck engine. Typically these are designed to run in the 2000 to 2500 rpm range. The 5.7 in my pickup rarely gets above 2000 rpm due to the advantages of an overdrive transmission. But in any case 50 to 100 k miles before a plug change.

A boat engine runs almost constantly at about 3400 to 3600 rpm. That's why I change plugs every other season, about 150 hours. I only have 8 and DIY, so it's no big deal.

As for DDD, it's time for new plugs.

Henry


Sent from my iPad using Tapatalk HD
 
Agree.
The ac plugs are platinum or double platinum
Probably good idea to change wires too.
Ron
 
I too own a 2008 330 Dancer and I just changed my plugs. If you purchase them from MarineMax they will charge you $16+ each. If you go to AutoZone you can pick them up for $6.50 each. Huge difference. Also, do not purchase Mercruiser wires unless you truly want to get hosed....$85 per wire. There are aftermarket vendors that are much cheaper. I just purchased an entire set of 16 for $85.
The correct plug is the AC Delco ACD 41-983
At that price I change mine every year. As stated previously, the plugs are cheap, the engines are stressed and 8.1s are notorious for eating plugs.
IMYO,

Peter
 
Carbo, what's the equivalent at Autozone that costs $6.50? Big difference in price.
Aren't these motors "distributorless?" Can you get just the wire?
 
Not just autozone...
I bought the plugs from Advance auto parts. $6.49 ea
AC 41-983
ron
 
RONDDS,

In response to your question, the $6.50 price I quoted was for the plugs themselves. My comment re the wires was that the OEM wires are ridiculously over priced and one can get even better aftermarket wires for 496s essentially 16 times cheaper, i.e. a set for both engines vs one wire.
Peter
 
Peter and Ron...
I get it now. You're saying that AC 41-983s can be had at an auto parts store for $6.50 each. Understood. What's the source for the wires (aftermarket)? Best price I could find for a set of 8 Mercs is HERE. OUCH.

And Carter, thanks for breaking the story ;-)
 
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rondds said:
Peter and Ron...
I get it now. You're saying that AC 41-983s can be had at an auto parts store for $6.50 each. Understood. What's the source for the wires (aftermarket)? Best price I could find for a set of 8 Mercs is HERE. OUCH.

And Carter, thanks for breaking the story ;-)
Click to expand...


I bought a set from Rock Auto
http://www.rockauto.com/catalog/emailpagetofriend.php?ni=110
not sure if the link will work, but if you go to the site, go to marine, look up engine and there are two options
 
Ron, dead link but I think I found what you linked to. Rock Auto sells an equivalent for $133 a set. United Ignition Wire Part # 116 - Mega Mag - it's a cross match to Merc 84-881698. Better but steep.

I still don't get it though...Distributor? No distributor?
 
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Distributorless ignition system that eliminates mechanical timing adjustments............

Rock sells two brands. United Ignition is higher end.
There is also a set from Standard Motor Products for $85.
That reminded me too much of my youth working on cars....SMP made Blue Streak and what we always used..

My next issue before launch is to sort out and see if i have the Cool Fuel III problem.
UGH
 
Ok Guys, I posted this question on another blog but never got an answer. How in the F^^k do you get the oem clamps off of the oem spark plug wires. Short of cutting them of and rigging some new "Zip Ties", I don't know what to do...:huh::huh::huh:
 
So where does the spark plug wire go when it leaves the spark plug (forgive my ignorance - I'm used to a 1989 Thunderbolt IV - no points, but still pretty primitive).
 
rondds said:
So where does the spark plug wire go when it leaves the spark plug (forgive my ignorance - I'm used to a 1989 Thunderbolt IV - no points, but still pretty primitive).
Click to expand...

Well, that depends. On my boat it goes to the coil for that cylinder.
 
rondds said:
So where does the spark plug wire go when it leaves the spark plug (forgive my ignorance - I'm used to a 1989 Thunderbolt IV - no points, but still pretty primitive).
Click to expand...
Ron, the 8.1's have coil packs, individual coil for each cylinder mounted above the valve covers.
 
Ok. Got it. Like my Honda Pilot. I've logged about 200 hours working on old big blocks, and probably 3 minutes on newer car engines, and of course, ZERO on an 8.1 Merc. Thanks for the explanations!
 
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