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Otto Throttle 
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Joined: October-02-2017 Location: Cleveland OH Status: Offline Points: 405 |
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 Topic: Spark Plug SelectionPosted: March-01-2025 at 10:41am |
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Ok I don't mean to "Spark" any controversy but here goes....
Spark Plugs...Mine HO, 285 HP, Carbureted (GT40 Heads) calls for the WL764s. I have seed both the standard, copper, and platinum electrode versions....I am still running the factory original plugs, but I want a spare set...just in case. What brand and electrode are you running out there! Thanks in advance! Otto
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Otto
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TRBenj
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Posted: March-01-2025 at 3:23pm |
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Standard is copper and the best conductor- should offer the best performance and lowest price. The advantage of the platinum and iridium tips are longevity, you’re usually best served running the copper and replacing them more often.
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Otto Throttle
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Posted: March-01-2025 at 5:54pm |
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Thank you!!!
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Otto
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Jonny Quest
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Posted: March-01-2025 at 6:57pm |
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Some have indicated that the Autolite 764 is discontinued. They can still be found, especially on the internet.
The Autolite 104 is the replacement plug for the 764 and is basically the same plug -- 104 has full threads on the body and the 764 is threaded halfway. Either will work. (GT-40 or GT-40P heads) JQ
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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KENO
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Posted: March-02-2025 at 5:53pm |
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One thing to keep in mind here is that
A copper plug typically has a nickel center electrode with a small diameter copper wire buried in the middle of the center electrode A platinum plug has that same small diameter copper wire buried in the middle of the platinum tipped center electrode An iridium plug has that same small diameter copper wire buried in the middle of the iridium tipped center electrode You can't visually look at any spark plug and see any copper. (unless you destroy the plug to get at look at it) And like mentioned earlier, the copper core standard plug will be just fine in your engine Otto And Otto..... you should probably change those plugs a little more often than every 27 years or so.
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Otto Throttle
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Joined: October-02-2017 Location: Cleveland OH Status: Offline Points: 405 |
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Posted: March-03-2025 at 9:49am |
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What is the difference between full threads or half threads? Does one run cooler than another?
Yea I know… my cousin has the same boat except an 1998, and he has never changed plugs either! He has 400 hours on his and I have 500 on mine. I was thinking when changing them to soak the threads with kroloil for a few days….. That being said we are checking driveshaft alignment and repacking the rudder and drive shafts this spring! Any tips on those projects? |
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Otto
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Otto Throttle
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Posted: March-03-2025 at 10:06am |
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Also what do the prefix’s mean before the number…. WL or AR… what if there are no prefixes?
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Otto
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Jonny Quest
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Posted: March-03-2025 at 10:11am |
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Full Threads vs. Half Threads The thread length shouldn't affect anything. I believe that you are thinking about the plug's heat rating. Per the Autolite catalog, both the 764 and 104 plugs have a heat rating of 9. I ran both the 764 and 104 in my 1994 and 2001 boats -- both with the High Performance Ford 351W. Just for giggles, I change spark plugs every couple of years. My OCD lizard brain... Anyway, I would pull the plugs and they both looked and performed the same. JQ
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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Jonny Quest
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Posted: March-03-2025 at 10:18am |
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Autolite CopperSpark Plug - 764
Spark Plug - 104 Specifications:
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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Jonny Quest
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Posted: March-03-2025 at 10:30am |
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Autolite spark plug prefix list:
XP = Iridium AI = Ultra Iridium AP = Platinum APP = Double Platinum JQ |
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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KENO
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Posted: March-03-2025 at 2:33pm |
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Jonny didn't exactly answer this question for you If you had an AR764 for example, that's an Autolite rrrrrracing plug. You dion't need any of those. You won't find a plug with WL764 stamped on it anywhere......but if you look at White Lake Marine's nautiqueparts.com you'll see them selling a plug with their part number of WL 764. It's the same Autolite 764 that you can buy anywhere else. No difference in the plug itself....none at all. A regular ol' copper core 764 has no prefix in front of it. It just says Autolite 764 on the plug So if you had a WL764 in your hand and read the stamping it would say Autolite 764 There's plenty of mumbo jumbo out there from all the spark plug outfits to keep you confused |
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Otto Throttle
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Posted: March-03-2025 at 3:01pm |
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I figured that was the case, I guess with the more confusion, get people to buy the wrong stuff the first time around, and then after they come to a place like this, they find out what they really need! I will go to my local car parts store And support something local!
Thank you for clearing that up, I know spark plugs make a difference. My Evan tech has indexed plugs. That’s a whole Nother topic. This place is an underrated source of information! Thank you everybody |
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Otto
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Otto Throttle
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Posted: March-03-2025 at 6:31pm |
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One last thing and I think we covered it… resistor vs non resistor plugs… pros, cons, and and applications?
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Otto
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KENO
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Posted: March-03-2025 at 7:16pm |
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Resistor or suppressor type plugs are what you want.
They both do basically the same thing and minimize RFI
The 764 are suppressor The 104 are resistor Non resistor sounds sexier and more powerful.......but you don't want them, especially with any electronics on the boat. Now your mission is to go buy some 764 or 104 plugs or it it makes you feel better you could some would say, waste, I mean spend a little more for AP 764 or AP 104 for a somewhat longer plug life |
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Otto Throttle
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Posted: March-03-2025 at 8:20pm |
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Cool! How do the put resistors in the plugs? Are they in line and actually cast into the insulator? Or Is it the way the electricity is routed through the plug, do they change the phase of the electricity before it hits the electrode and discharges? I know we had to manually match the phase/frequency on the 727 before we could bring them on line.
Electricity is amazing |
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Otto
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KENO
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Posted: March-04-2025 at 9:39am |
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[QUOTE=Otto Throttle] How do the put resistors in the plugs? Are they in line and actually cast into the insulator?
QUOTE] I suppose different brands might do things differently, but as a general rule, they're a separate resistor that's cast or inserted into the insulator
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MrMcD
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Posted: March-05-2025 at 1:05pm |
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Std Copper plugs work perfect in a boat application. The Copper plugs fire with the least amount of energy. This is good as many boats still have standard distributors and do not have high energy systems. The only negative is standard copper plugs wear faster. So they only last maybe 10,000 miles in cars. In a boat that might be 500+ hours? So many years of service and they copper plugs are so inexpensive they are a great choice in boats with standard distributors.
Platinum plugs were the first long lasting plugs offered, they came about to handle the high energy ignition systems first introduced int he 90’s. First single platinum and then double platinum plugs came out. They can last 100,000 miles in cars but the negative is it takes more energy to fire a platinum plug so they only work well in high energy systems. Iridium plugs are fantastic plugs, they can last well over 200,000 miles in car applications. They fire with less energy than the platinums so that is another plus. They use fine wire technology which gives a more focused spark, all good. These are basically lifetime spark plugs. The only negative is they still need more energy to spark than a standard copper plug. So you are out on the water, been relaxing listening to your tunes, time to start your boat and head home. The battery is low so the engine cranks slowly. The best plug in this case is the cheap standard copper plug. In a standard ignition system (not high energy ) the copper works best as it will make a spark in the lowest energy situations and maybe get you started. IF copper plugs are used in a high energy system they will wear fast because the high energy spark will blow particles off the electrodes as the engine runs and slowly open up the gap of the spark plug, They would still last 5,000 miles or more in a car. In a boat that is probably a couple hundred hours at least. In a 1995 or newer boat I would consider Iridium plugs as a never change again option. In boats with points in the distributor ignition systems I would stick with the std copper plug options. I am not a fan of the platinum or double platinum plugs due to the high energy required to fire them but they came in millions of cars and did outlast copper.
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KENO
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Posted: March-05-2025 at 4:08pm |
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Here's a link below with input from the Director of Engineering at Autolite that doesn't exactly agree with what was written above about what type plugs fire easier. And keep in mind that what's commonly called a copper plug has a copper core inside the center nickel electrode. A platinum plug has a platinum tip on the center electrode. The electrode is still nickel with copper in the middle. Double platinum has platinum on the tip of the ground electrode too Iridium same copper core surrounded by nickel with really fine iridium tips But we probably all agree that in this thread about a 351w with gt40 heads, the normal nickel electrode with copper core works just fine and platinum or iridium will work just fine for longer and depending what you buy, can be pretty pricey. Sometimes old myths die hard, kinda like synthetic oil being too slippery
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Otto Throttle
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Posted: March-05-2025 at 6:07pm |
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Thank you everybody for replying to my post. My next question that I was going to ask is do I have high energy ignition in my 1999, and I take by one of the previous posts that my 1999 does. If you take a look at the shape of an aviation Plug it is totally different. It is amazing how so many things we take for granted are purpose built. I think I am going to stick with good old copper, and change my spark plugs every 20 years! It would be interesting to compare performance of those individual spark plugs relative to the type of gas being used.
Since my boat sits on a trailer 99% of the time I use the super unleaded from Costco. I run 93 pure gas in my Evinrude E Tek but it burn a lot less! It’s 7 bucks a gallon. |
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Otto
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MrMcD
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Posted: March-05-2025 at 9:56pm |
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My info is second hand but direct from he engineering staff at Champion Spark Plugs. The company I was with purchased Champion back in 1997 and I was with them till 2019. What I shared is the straight scoop from Champion take it for what it is worth.
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KENO
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Posted: March-06-2025 at 7:48am |
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Otto Throttle wrote: