spark plugs

[dino]

This is my second season owning the boat not changing spark plugs. Have had no problems, but in the spring they are coming out. I have been told that the plats last a long time although you need to change them because they get rusted and are tough to get out. On that, is it worth putting in the platinums or buying regular ones since you need to change them because of the corrosion factor.
Thanks

 

[jason78]

This is my second season owning the boat not changing spark plugs. Have had no problems, but in the spring they are coming out. I have been told that the plats last a long time although you need to change them because they get rusted and are tough to get out. On that, is it worth putting in the platinums or buying regular ones since you need to change them because of the corrosion factor.
Thanks

I switched to AC-Delco Iridiums and am very pleased with them. I have been told that you should not fog the engine with Iridium plugs and that is fine for me. Not sure if it is true or not. One thing I would say is to stick with the AC Delco Plug Merc recommends.

Here is a thread that willhelp you. Pay attention to the Service Bulliten posted in Post#14. There were some errors in the original plug spec. The recommended plug is a Platinum.

http://clubsearay.com/forum/showthread.php?t=25595&highlight=boafft

Jason

 

[33ec]

I just changed all mine and used the platinum plugs. they can be hard to come by at automotive shops. I would stick to the recommended plug as well. I found platinums to be $10-$12 each for the correct plug and non platinum automotive plugs to be in the $2.50 each range. the engines will run on the automotive plugs but performance and longevity are the issue. I have experienced no problems with corrosion on spark plugs regardless of plug type. I would suspect that corrsioon issues have a lot more to do with environmental conditions and maintenance in your engine room.
Good luck.

 

[Presentation]

I just changed all mine and used the platinum plugs. they can be hard to come by at automotive shops. I would stick to the recommended plug as well. I found platinums to be $10-$12 each for the correct plug and non platinum automotive plugs to be in the $2.50 each range. the engines will run on the automotive plugs but performance and longevity are the issue. I have experienced no problems with corrosion on spark plugs regardless of plug type. I would suspect that corrsioon issues have a lot more to do with environmental conditions and maintenance in your engine room.
Good luck.

Just to add a bit more, the $18/each spark plug Mercury recommends for my motors are for sale at Napa for $6/each.

The spark plug is the exact same AC Delco part number and is the exact same plug.

The only difference is where I purchased them and how much I paid.

 

[sbw1]

I've changed my plugs once since owning this boat which we bought new in 2004. If memory serves they were changed two years ago. They actually looked quite good and there was no sign of rusting. Maybe it's the 8.1s vs. the plugs, but I did not notice any difference in fuel use or performance after the change. My 454s would go through plugs like a hot knife through butter.

 

[Great lakes pirate]

My manual says to use AC 41-932 plugs. Service Bulletin says AC 41-993 replaces AC 41-932 but they are interchangeable. The bulletin calls out the 932 plugs. What is everyone else using? I am going to change the original 2003 wires as well. Should I do the dist/rotor while I am at it? 600 hours on the engines.

 

[billnpat]

My manual says to use AC 41-932 plugs. Service Bulletin says AC 41-993 replaces AC 41-932 but they are interchangeable. The bulletin calls out the 932 plugs. What is everyone else using? I am going to change the original 2003 wires as well. Should I do the dist/rotor while I am at it? 600 hours on the engines.

I would change everything.....:thumbsup:

 

[promocop]

When I had to change plugs on my Merc 8.1s the local Marine Dealer wanted to charge me almost$20 a plug. Thankfully he had only two in stock so I went down the street to Napa and bought them for $5.75 each. And these so called local marine stores/dealers wonder why we don't buy from them. Their thinking is that as boaters they can rip us off!

 

[Lazy Daze]

Their thinking is that as boaters they can rip us off!

I'm sorry, but I have to weigh in on this one. That is an unfair statement to make. Dealers don't charge an exorbitant mark-up on marine products "just because". The mark-up is generally same across the board. The sole reason that certain items (8.1 plugs, especially) are so high at marine stores is simply due to the supply chain. It's not the dealer's fault - it's simply due to a dealer's source for a particular product (and what that source is charging the dealer, and what the source's source is charging, etc).

That being said, I'm a consumer too. I look for better deals, as well (as long as I'm getting OEM quality - or better - from a reputable company). If I owned 8.1's, I would get them from NAPA. But, to say that the dealers are "ripping people off" is absolutely not fair. I obviously can't speak for all dealerships, but I can tell you straight out that no-one who works at Peters Marine is rich because of selling spark plugs. Just trying to make a living.


OK, back to the OP... I wouldn't change them "just because it's been a couple of years". Also, the rusting thing is by no means common place. If it was me, I'd physically take a look at the exterior and then pull one or two from each side (front and back) to assess the condition. Don't go crazy here - just do the ones that are easy. Your engine uses a true injection system, as opposed the system found in earlier boats (like mine). As such, plugs generally last longer in systems like yours. With my engine, I wouldn't even consider it after only two years. Of course, if you're putting on tons of hours each year, that would factor in. But, "reading" them is still the best way.

 

[billnpat]

I'm sorry, but I have to weigh in on this one. That is an unfair statement to make. Dealers don't charge an exorbitant mark-up on marine products "just because". The mark-up is generally same across the board. The sole reason that certain items (8.1 plugs, especially) are so high at marine stores is simply due to the supply chain. It's not the dealer's fault - it's simply due to a dealer's source for a particular product (and what that source is charging the dealer, and what the source's source is charging, etc).

That being said, I'm a consumer too. I look for better deals, as well (as long as I'm getting OEM quality - or better - from a reputable company). If I owned 8.1's, I would get them from NAPA. But, to say that the dealers are "ripping people off" is absolutely not fair. I obviously can't speak for all dealerships, but I can tell you straight out that no-one who works at Peters Marine is rich because of selling spark plugs. Just trying to make a living.


OK, back to the OP... I wouldn't change them "just because it's been a couple of years". Also, the rusting thing is by no means common place. If it was me, I'd physically take a look at the exterior and then pull one or two from each side (front and back) to assess the condition. Don't go crazy here - just do the ones that are easy. Your engine uses a true injection system, as opposed the system found in earlier boats (like mine). As such, plugs generally last longer in systems like yours. With my engine, I wouldn't even consider it after only two years. Of course, if you're putting on tons of hours each year, that would factor in. But, "reading" them is still the best way.

Thank you dennis about the spark plug issue,

Im having my mechanic take a peek at mine in the spring time and will change them if needed, i have no idea if, and when they were ever changed i have 450 hours on the engines 350 mercriusers...:huh:

 

[Havana Shamrock]

OK i;m confused which plug do i use for 2003 320 with 350 mag's ? i never received any manuals from the dealer, so it's all research for me, p.s. mercruiser mech told me to do caps and rotors every year anyone else do this?

 

[Presentation]

OK i;m confused which plug do i use for 2003 320 with 350 mag's ? i never received any manuals from the dealer, so it's all research for me, p.s. mercruiser mech told me to do caps and rotors every year anyone else do this?

Your spark plug part number and gap is listed on your engine cover, that big black plastic thing on the top of your flame arrestor.

Many of the AC Delco part numbers changed when they moved production over seas a few years ago.

My guess is you will see part number AC Platinum AC 41-932 which is now AC 41-933 and a required Spark Plug Gap 0.060 in. $18/each at your nearest marine supply store or $6/each at NAPA.

Do not use the coin tool when gapping a platinum plug. View a YouTube video on how to properly gap a platinum plug. Basically you don’t want to apply any force to the electrode in the middle.


On the "every year" thing, do you have your owner’s manual? You should see a maintenance chart in this manual.

Mercury says 3 years on changing the plugs, rotor and cap.

Many people agree that the above 3 year cycle is overkill with modern platinum plugs, fuel injection and electronic ignition. It’s been 3 years for as long as I can remember and before platinum plugs, fuel injection.

Of course a mechanic that has something to gain may suggest a far more frequent change of these parts.

I did it all this fall. First change in 7 years. The plugs I removed looked excellent. Same with the rotors and caps.

 

[l-skynyrd]

Just going to add my $.02

I have bought the 993's for my girl friends boat which has
the 5.7 MPI engines from Summit racing.com and boat runs great.
The price is about $6.00 a plug and you can order on line and have them shipped to your house without leaving your couch. There is no difference in the plugs from the marine store and Summit racing. A plug with the right number is the same no
matter where you buy it. A little common sence will go a long
if you chose to use it..........


Len