www.iFourWinns.com

I "used" to be that guy who'd change the spark plugs annually, regardless of hours.

It didnt take long of replacing spark plugs that looked new every season, barely worn, that I realized I was maybe un-necessarily spending money I could be spending on other maintenance items.

Lately, I put 40-50 hours on per boating season. Right now I have ~95 hours or so on the Champion RS12YC spark plugs (They were Volvo Penta OEM plugs I replaced in 2012). My engines are TBI 4.3l's and I use street gas (read: e10, 87 octane). I used anti-seize on the threads and di-electric grease on the boots when I did the plugs last. I have no issues with starting, idling, or performance.

With that being said, how often should I be replacing the plugs? Does the interval increase with EFI engines vs. carbed? Or should I be changing sooner since I use auto gas?

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1997 Four Winns Vista 278
T - 4.3l EFI
Kohler 4esz Genset
379 hours as of 8/8/21

In my history, I would say that I changed plugs around once every 3-5 years or longer. I would occasionally pull one out and look at it's condition. Certainly, if I started to hear any misfire, then I would change plugs, cap and rotor. Spark plug wires at about 15 years.

On my 2000 Horizon 240, which purchased 2 years ago, I changed the plugs, and they looked like they were the originals. They had visible wear, but were not that bad. (had about 450 hours)

So in my opinion, changing them every year sounds like a waste of money. Maybe every 3-5 years? Or 300 hours?

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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings

Thanks.

When I replaced the spark plugs in 2012, the Volvo Penta replacements were Champions (yuck!). Its been bugging me ever since. Traditionally, I have always used ac-delco plugs in a GM block. MR43LTS or one of its variants.

However, seeing that Volvo is putting Champions in a GM block and Ive used them two years and the engine hasnt imploded, instead of going with the Delcos I put on my big boy pants and finally bought some NGK's!
They were $1.60 or so at rockauto and they got a much higher recommendation from what Ive read on the boating forums than the delcos.

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1997 Four Winns Vista 278
T - 4.3l EFI
Kohler 4esz Genset
379 hours as of 8/8/21

This is good info. Thanks
I was wondering how often they should be changed as well. As far as I know my boat still has the original plugs. At just over 200hrs I'm thinking this spring is a good time to change them.

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2004 248 Vista "Amante"
MC 5.0MPI/B3

I just changed mine (likely for the first time as I am the second owner) along with the cap and rotor as part of my end of season maintenance. Cap and rotor looked more worn than the plugs. I would agree that 250-300 hours seems appropriate.

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Norris Lake, Stardust Marina, Andersonville, TN
2005 Four Winns 230 Horizon 5.7L Volvo Gi/DP
2001 Maxum 1900SR 5.0L V8 (Sold)
2011 Nissan Armada Platnum

It will depend on a few variables, as to the frequency of replacement:

Carb?
EFI?
Platinum/ Iridium?
Fuel type?

With conventional copper style plugs, it's cheap insurance to replace annually.

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2011 Four Winns H180 SS.
Aussie built Mustang 2800.
SOLD - 1997 Four Winns Horizon RS