phebus

What is the plug number through GM? Thanks, I need to replace mine, but boat is in storage, and want to have them the next time I go out.

Vyper340

When plugs were pulled at 200 hours they looked perfect. It was an unnecssary change and there are 2 plugs that are a bear to get to and get out because of excellent engineering.

Reckless32

Mercruiser service manual says to simply "check" spark plugs/wires every 300 hours or 3 years. Later in the manual it refers to inspecting both and says look for cracks, general condition etc., and to pull inspect, re-gap plugs. Unless you're experiencing problems changing plugs/wires before their time is overrated. Same with cars, trucks, etc. Wanna change something very frequently, do the engine & drive oils. That's what will ruin your day.

epeek

Thats true. Todays fuel injected engines run very clean.
Changing plugs every 60 hrs is a waste.

Raylar

Platinum tipped plugs that come stock in the 496's should go at least 200-300hrs with good fuel and engine running properly. Be careful how you clean them, the platinum tips are very fine and can be easily damaged, keep the gaps at .060" and don't blast or wire brush them, alcohol or Berrymans and a tooth brush are adequate.
We cary these AC Delco plugs in stock and we sell them for $7.00 per plug while supplies last. We also have about 6 sets of stock new take off plug wire sets that we are selling for $75.00 per set. All plus UPS.

Ray @ Raylar

Reckless32

Good info Raylar. I'm at 177 hrs so I have a ways to go and the motors are still running very smooth (knock on wood; "knock" "knock"). As time passes by and the earliar model 496's reach the 3-400 hr mark those plugs/wires are soon to become a hot commodity as will everything else about these motors.

Macklin

Here are the results of a little research I recently did and emailed to my club:

My motors currently have Denso #TJ14R-P15 plugs. No auto parts shops seem to carry them locally. Lynnhaven Marine has them for $10.71 each – Volvo part #386127. (Not sure if it is the exact same Denso plug.) Sparkplugs.com has them @ $6.80 each. They cross reference NGK #PZTR5A-15 as a match @ $11.71 each. Rodney ordered his plugs through a Merc dealer; part #33-863622001 for wholesale at $12 each. The plugs he got are AC Delco #41-983. LMC retails them for $17.27 each. They are available at Advance Auto for $5.98 each.

I plan to stay with the Denso plugs.