Correct Spark Plugs for a 2003 MercCruiser 5.0

[dclynch]

Hoping someone can tell me what is correct. I have a 2003 Bayliner 212 Capri CU. It has a 5.0 motor. I bought it used 3 years ago from a friend who purchased it new. I was doing a tune up and on the Air Cleaner it called for MR43T spark plugs and that is what the parts book also called for when I went to purchase them. To my surprise when I pulled out the first plug the originals are a AC 41-932 totally different plug. Now to make things a little more confusing when I went back to purchase these plugs I was told the new number is AC 41-933 and that number replaced the AC 41-932. I have changed them and had to order the Cap, rotor and plug wires which wont be in until Tuesday. Was hoping someone could tell me why it would have those plugs. Thanks and sorry for being long winded.

 

[Fun Times]

Hi there, and welcome to iboats!

Using the AC MR43LTS plugs will save you some money.

? Follow these guidelines for the correct spark plugs for carbureted MerCruiser engines: a. MerCruiser 4.3L, 5.0L, and 5.7L carbureted engines are shipped new with platinum AC 41-932 (P/N 33-884019) spark plugs, soon to be superseded by AC 41-993 (P/N 33-884019001). b. The recommended service replacement spark plugs for these engines are non-platinum AC MR43LTS (P/N 33-884019) or NGK BPR6EFS (P/N 33-816336). c. MerCruiser carbureted engines require a spark plug gap of 1.14 mm (0.045 in.). d. Mercury platinum spark plugs have a gap setting of 1.5 mm (0.060 in.). To reduce the possibility of installing the platinum spark plugs with the incorrect spark plug gap, the non-platinum spark plug is the recommended service replacement. e. The use of AC 41-932 (P/N 33-884019) or AC 41-993 (P/N 33-884019001) platinum spark plugs in a MerCruiser 4.3L, 5.0L, or 5.7L carbureted engine is acceptable if the spark plug gap is very carefully re-set at 1.14 mm (0.045 in.) from 0.060 in.......

Here's the service Bulletin No. 2006-03 - JustAnswer that will let you know what plug is safe to use...But the important part to read is quoted above for you.

 

[dclynch]

Thank You for the quick reply. I guess I will pull them back out and re-gap them. The strange thing is on the ones I pulled out I noticed that the gap was huge and when I asked about that at the parts store I was told engines that use those plugs don't need to be gapped.

 

[Scott Danforth]

I prefer the NGK's myself.

 

[dclynch]

Well good new tune-up complete. BAD news checked oil and have water in oil. Pulling the intake off today hoping it is just a intake gasket.

 

[dclynch]

I know this is old but just wanted to let you know what I found or didn't find. I was so disgusted and didn't have the tools to determine what caused the water in the oil so I was ready to take it in. I called around and everyone had a 4 to 6 week waiting list so I decided to check myself. The first thing I found was I forgot to put my thermostat back in when I un-winterized it. (long story about temp gauge not working) I had run the boat about 15 hours trolling in 40degree water so was thinking condensation, I also was told to check the exhaust shutters and found one was stuck closed so I replaced them also. I ran the boat on muffs for a couple of hours and did not have any water in the oil so I am not sure exactly where it came from. I am still trying to get the thermostat to work. I have replaced the sending unit and I have ordered a new thermostat also. The strange thing is when trolling the gauge will occasionally move up to about 150 then slowly fall back down. I have verifired the gauge works by running a wire to ground from the plug and the gauge will peg out. Anyone ever run into this issue?

 

[Bondo]

Ayuh,.... If ya haven't already done so,.... Change the raw water impeller,....

 

[Fun Times]

I forgot to put my thermostat back in when I un-winterized it...... The strange thing is when trolling the gauge will occasionally move up to about 150 then slowly fall back down. I have verifired the gauge works by running a wire to ground from the plug and the gauge will peg out. Anyone ever run into this issue?

If the thermostat is becoming defective or the O-Ring at the thermostat has been compromised in any way, the engine temperature may have an tendency to fluctuate.

Also the gasket with the 2 brass rivets at the intake manifold needs to be installed dry or it could affect the temp sensor/s grounding capability.

 

[dclynch]

Thanks Bondo I have not changed the raw water impeller I will do that right away.