Please note this thread has been inactive for 90 days. For the best results, please start a new thread.
Results 1 to 19 of 19
  1. #1
    Cadet
    Join Date
    Jun 2005
    Posts
    21

    Default Spark Pllugs for Chevy 350

    OMC recommends AC T43MR plugs. But this goes back many years.Does anyone know of higher performance plugs, i.e. more revs ,smoother idling? Platinum? Just put in some new Autolite equivilents and RPMs dropped by 200. Robert

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
    Join Date
    Aug 2004
    Location
    Western WA.
    Posts
    62,323

    Default Re: Spark Pllugs for Chevy 350

    Sure would help to know the year of your engine. Not all 350's are the same.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  3. #3
    Chief Petty Officer
    Join Date
    Apr 2003
    Location
    Cordelia Ca
    Posts
    495

    Default Re: Spark Pllugs for Chevy 350

    try this http://www.sparkplugs.com/results_cr...CrossWarning=1 It has all kinds of cross referenced plugs if your omc requires Delco MR43t spark plugs.Good luck

  4. #4
    Cadet
    Join Date
    Jun 2005
    Posts
    21

    Default Re: Spark Pllugs for Chevy 350

    The Chevy 350 is about an 1983 version. I nave the manual and its recommendation.Just wondered if some state of the art stuff might be around that folks knew about Thanks, Robert

  5. #5
    Petty Officer 1st Class
    Join Date
    Jul 2002
    Location
    NY
    Posts
    379

    Default Re: Spark Pllugs for Chevy 350

    Bob, Car enthusizsts have a tendency to experiment with things... "SplitFire" or "Platinum" spark plugs, different wires, advanced timing, remaped fuel/air ratio etc...I have purchased my boat from a racer, who installed "SplitFire" plugs into pre-1986 350 Merc. When I got the boat, one engine was hidrolocked. When I took off heads, one head gasket was blown and the cylinder head had a crack. Top of pistons had grooves in them. The grooves looked like someone took an electrical welder and did a sloppy job welding the pistons.I asked the shop mechanic to look at it and determine the cause for problems.Verdict:"SplitFire" plugs caused an extra heavy spark which with time had caused damage to the top of pistons. Engine ran at hotest temperature at all times. Overheat caused blown head gasket which in turn caused water to enter cylinder. Unless Don S could contradict to this, I strongly suggest: Use what is recommended by MERC. Any deviation from OEM may actually harm the engine's parts in the long run. You have performance over damage on the scale... What's worse more is your call.

  6. #6
    Petty Officer 1st Class
    Join Date
    Jul 2002
    Location
    NY
    Posts
    379

    Default Re: Spark Pllugs for Chevy 350

    Any deviation from OEM may actually harm the engine's parts in the long run.
    Just to refrase this: I think it only should apply to this particular case, case of spark plugs. Some changes from OEM as thruhull, less restrictive exhausts, better compartment ventilation, lighter weight manifolds and risers will by no means hurt the boat's engine. Don S, Bondo, please correct me if I am wrong

  7. #7
    Cadet
    Join Date
    Jun 2005
    Posts
    21

    Default Re: Spark Pllugs for Chevy 350

    Lenny, Thanks for your advise.I will stay with the manufacturer's call out on the plugs.It certainly sounds like a good idea based on your experience. Thanks, Bob

  8. #8
    Petty Officer 2nd Class
    Join Date
    Jan 2005
    Location
    Fairview, NC
    Posts
    193

    Default Re: Spark Pllugs for Chevy 350

    I have been running AC RapidFire #1 plugs for 4 years and have never had one foul out. I do alot of Idling and I fog my engine after each use.

  9. #9
    Moderator Bondo's Avatar
    Join Date
    Apr 2002
    Location
    The Mouth of the Chaumont River, Ny.
    Posts
    52,669

    Default Re: Spark Pllugs for Chevy 350

    There's All Kinds of Fancy Looking, Pretty Sparkplugs out there....... Most Co$t Much More than the MR43Ts,..............I've Never,.. Ever been failed, or let down by a MR43T Plug,..... Ever........I'd rather spend my money on somemore Gasoline,... Than Over-Priced SparkPlugs........That's My Opinion,........
    Any Grease is Better,..... Than No Grease at All.......

  10. #10
    Vice Admiral Scaaty's Avatar
    Join Date
    May 2004
    Location
    West Coast (PNW) Salty Dog
    Posts
    5,099

    Default Re: Spark Pllugs for Chevy 350

    Originally posted by Bondo: I've Never,.. Ever been failed, or let down by a MR43T Plug,..... Ever........
    And I agree..........(but there is no way I will believe the BS about splitfires)

  11. #11
    Rear Admiral
    Join Date
    Jun 2004
    Location
    NY
    Posts
    4,267

    Default Re: Spark Pllugs for Chevy 350

    In Dennis Moore's book, "SBC Marine Performance", he recommends the extended tip versions of the MR43T, but I have only found the non-marine R43TS. NGK also has an extended tip version plug for the older 350 chevies. While his book has been out a long time and his explaination of why they are better, and seems to make sense, I have not heard testimonials on boating boards about using them. I did find that Crusader specs some for their 350 chevy's with the old style heads. The newer Vortecs do use an extended tip, as well. I have read on some other boating boards about a specific Champion plug that was designed specificly for Mercruisers 350's, because of a fowling problem. From what I can tell, it had something to do with the clearance between the plug and the exhaust manifolds. Apparently, the standard type is too close, picking up heat from manifold, and not being able to pull the heat away from the cyl head. It was also stated that if you replaced your plugs, every year, it wouldn't become an issue, and since they were Champions, I didn't figure it was worth trying.

  12. #12
    Petty Officer 1st Class
    Join Date
    Jul 2002
    Location
    NY
    Posts
    379

    Default Re: Spark Pllugs for Chevy 350

    Originally posted by Bondo Robby6950..........(but there is no way I will believe the BS about splitfires)
    I will take a picture of the block that I have sitting in my garage. All components are 30 hours old. Engine ran with splitfires plugs. I would like to ask you Robby to comment on what will be on the picture (top of pistons) and maybe explain to me what might have been a cause for such damage within first 30 hours of using rebuilt block. It might as well clarify the BS - as you kindly expressed yourself in regards to my comments.

  13. #13
    Vice Admiral Scaaty's Avatar
    Join Date
    May 2004
    Location
    West Coast (PNW) Salty Dog
    Posts
    5,099

    Default Re: Spark Pllugs for Chevy 350

    I'm calling BS on the splitfires, always did, always will. Spark only jumps to ground, and the easiest one at that............. SplitFire" plugs caused an extra heavy spark If your mechanic believes that a spark plug is making "extra heavy spark".....and you are here asking for a second opinion, well, you are getting one. The coil and Ignition system make ALL the juice, never the plug. 42 years of 350's and Harley's tell me that this guy raced these motors hot and on the edge of detonation, and those marks are melted aluminum from that, not the plug........run the 43's, everyone else does. And check the timing......

  14. #14
    Moderator Bondo's Avatar
    Join Date
    Apr 2002
    Location
    The Mouth of the Chaumont River, Ny.
    Posts
    52,669

    Default Re: Spark Pllugs for Chevy 350

    Well,................I Gotta Agree with Robby............Spark plugs,.......Any Sparkplugs,......... Even Sparkplugs that are Too Hot,..........Don't Burn Holes in Pistons..................Detonation,..... Spark-Knock,....... Pinging,..... Pre-Ignition,.........That's what Burns Holes in Pistons...............
    Any Grease is Better,..... Than No Grease at All.......

  15. #15
    Petty Officer 1st Class
    Join Date
    Jul 2002
    Location
    NY
    Posts
    379

    Default Re: Spark Pllugs for Chevy 350

    Bob197, I was in no way trying to mislead you with what I said about SplitFires. My marine tech said SplitFires caused the top of pistons to melt...I would less likely stay with that version of the story. Bondo is a very knowledgeable and well known IBOATS forum member. I would listen and follow his opinion over my mechanics' as well as my own. Latest issue of Boating magazine suggested that "SplitFire Platinum" would increase both - speed and mpq by +0.75 and +0.25 respectively. I would like to apologize for giving you slightly wrong info. It is just that after I had to replace the block, I am a bit skeptical about none OEM parts. It was beyond my reasonable understanding how 30 hours of usage could kill 350 Merc engine. Mechanic mentioned SplitFires might have been an issue, so I replaced plugs to OEM recommended and decided to stick with it. I now remember running SplitFires in my Nissan Maxima. I tuned the car for performance and among the mods were sparkplugs. Did not hurt, but no visible power increase. On the other hand, free flow exhaust system, straight pipe in place of cat converter and a cold air intake was something of visual power increase. Robby, Bondo:Thank you for clarifying

  16. #16
    Vice Admiral Scaaty's Avatar
    Join Date
    May 2004
    Location
    West Coast (PNW) Salty Dog
    Posts
    5,099

    Default Re: Spark Pllugs for Chevy 350

    I tried Splitfires in my 79 Harley Shovelhead in the 80,s and for some reason they came out. I don't remember why, but still have them (I never throw anything out!), and in fact I just put them back in a month ago, as the Bosh Plats were fouling out (built motor-big carb/cam-also beginning to believe Bosch Plats a junk too) and I will now try something different after I run the Splits for awhile. I notice zero improvement, and I have rode this bike for 25+years. Still believe Splits are hype, as the Bosch with FOUR ground electrodes. And now $12 IRIDIUM plugs from Denso......I give up. If you want the best improvement, put a total MSD ignition system in. Seems they have risen to the top electrical wise. And a terrific book on electrics "The Doctor's Step by Step Guide to Optimizing your Ignition", written by Christopher A. Jacobs Ph.D, is great.

  17. #17
    Petty Officer 2nd Class
    Join Date
    Jan 2005
    Location
    Fairview, NC
    Posts
    193

    Default Re: Spark Pllugs for Chevy 350

    A projected tip plug- any projected tip plug will stay cleaner and therefore missfire less than one that isn't a projected tip, if the heat range is correct. If a spark plug has too cold a heat range it will not 'clean up' and will foul out. Too hot a heat range will cause electrode failure and may cause detonation as it acts like a glow plug in a diesel engine. A 'high end' plug is made of materials which can handle more heat without failure. I like the ones that unshroud the center electrode like the AC rapidfire or Nipendenso better than the splitfire.

  18. #18
    Petty Officer 2nd Class
    Join Date
    Dec 2004
    Location
    Algonac,Mi.
    Posts
    135

    Default Re: Spark Pllugs for Chevy 350

    allright this is getting as good as oil threads----Robby6950, I run autolite's in my 80 shovel never a problem.

  19. #19
    Chief Petty Officer
    Join Date
    Jul 2004
    Location
    Ventress,La.
    Posts
    512

    Default Re: Spark Pllugs for Chevy 350

    Will mr44t work on a pre vortec 350?

Similar Threads

  1. Switching from SB Chevy to BB Chevy
    By CaptnReinell in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 8
    Last Post: December 15th, 2009, 09:27 PM
  2. No Spark/Good spark/Intermitent spark 3 cylinder mariner 75hp
    By ellie271299 in forum Mercury & Mariner Outboards
    Replies: 3
    Last Post: July 14th, 2009, 01:30 PM
  3. 305 chevy to 406 chevy swap, V/P 280
    By floater3 in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 15
    Last Post: August 13th, 2008, 10:49 AM
  4. chevy 4x4
    By dansoph in forum Non-Boating Technical Topics
    Replies: 7
    Last Post: January 7th, 2005, 06:08 PM
  5. spark plug gap for 5.7L chevy
    By diew in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 2
    Last Post: July 26th, 2004, 06:44 PM
  1. iboats Forum Directory - Over 100,000 forum posts organized by topic