Which spark plugs?

[Jetter]

My boat is an 08 Z1 with Marine Power 5.7 GM Vortec engine. I want to do a tune up over winter and having a hell of a time locating proper part numbers. Firstly spark plugs. Marine Power Engine manual says AC 41-932 which no longer exists. Replaced by 41-993 as far as I can tell but the gap on those is different (.059 vs .060). The Marine Power Parts Manual shows part number 479111 which translates to AC 41-101 which adds to my confusion. Just wondering what plugs others with same motor are using and which brand they prefer?

Also Parts Manual shows distributor part number (480359) but doesn't give the numbers for just the cap and rotor. I think it's ACDelco D329A and D465 but just not positive.

Any help would be appreciated.

[TeamAllen]

Have you tried this site for parts? It was recommended on another thread by someone else.
https://marineenginedepot.com/MP/Default.aspx

[Jetter]

Have you tried this site for parts? It was recommended on another thread by someone else.
https://marineenginedepot.com/MP/Default.aspx

Many times as well as every other. My question is not where to buy parts - it's which parts to buy.

[UNSTUCK]

Personally I'd walk into my Napa store and purchase any plug that fit and was in the right heat range. And I certainly wouldn't lose sleep over a plug that was .001" gap differance than what my plug is supposed to be. You buy 8 of any plug and they won't all be gapped to .059" or any number for that matter, anyways. And your gap gauge isn't exact enough for you to know either of those numbers with confidence.

[JTs-rz2]

Rockauto.com has that plug if you want it

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[browntrout]

Personally I'd walk into my Napa store and purchase any plug that fit and was in the right heat range. And I certainly wouldn't lose sleep over a plug that was .001" gap differance than what my plug is supposed to be. You buy 8 of any plug and they won't all be gapped to .059" or any number for that matter, anyways. And your gap gauge isn't exact enough for you to know either of those numbers with confidence.

I used to think a plug was a plug, I bought a 04 24v last fall and couldn’t get it running right. After a bunch of headaches it turns out automotive grade AC Delco plugs were used in a tune up. Shop switched them out to iridium and it’s run like a champ all season [emoji848].


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[cltTige]

Check out this post: http://www.tigeowners.com/forum/show...-plugs-and-oil

In the end I don't think .59 vs .60 is going to make a difference. Just make sure you get the right type one. Meaning if it calls for iridium don't get platinum ones. Probably what happened to browntrout.

[UNSTUCK]

I used to think a plug was a plug, I bought a 04 24v last fall and couldn’t get it running right. After a bunch of headaches it turns out automotive grade AC Delco plugs were used in a tune up. Shop switched them out to iridium and it’s run like a champ all season [emoji848].


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I completely agree that a plug is not just a plug. However, your engine running better because a (most likely) platinum plug was replaced by an iridium plug is suspect. Assuming the "right" AC Delco plug had been installed to begin with, and then switching to the "right" iridium plug nets you only two things: Longevity (roughly a bit over 2000 hours of use in a boat) and lower voltage resistance through the plug. Just a guess, but if your engine ran better afterwards it was likely because of the lower running resistance. This makes a failing plug wire, coil, or other ignition item appear to be working normally, when it's actually under performing.
Be careful swallowing the "automotive grade" coolaid. I have far more Motorcraft parts on my engine than I do Indmar parts. Automotive grade is proving to work just fine in the marine industry.

[boatwakes]

The AC Delco 41-993 is available at ANY auto parts store and not just used in marine applications. Iridium or platinum in this case won't matter and the difference of .001" isn't even an issue on those motors. Be aware there were aftermarket casting problems with the stupid crab caps for those motors but if you buy OEM, Mercruiser, Volvo Penta or Crusader there was no problem. BTW, all those brands are interchangeable for ignition, injectors and IAC's. LOL on running automotive parts on your motor...freshwater is much more forgiving than saltwater but ruining a weekend because you didn't want to spend $100 on a $15,000-$150,000 boat...?!!!

FYI, change your plugs, wires, cap and rotor every 2 years or 300 hours (time or engine time, do it) and plan on injectors at or around 500. From MANY experiences this will save you buying a new motor.