4.3GL spark plugs - which length?

[USA_boater]

My boat has the OEM AC 41-932 plugs...we know they cross to the 41-993 since the 932 is discontinued...both of those p/n plugs have a longer thread length when compared to the copper plugs that came in the older motors. When you attempt to cross the numbers (like if I wanted to go NGK), too many choices come back...looks like there were short and long thread plugs for the 4.3V6 marine engines. You can see in the vid below the difference and how someone else was confused. So would the '04 VP 4.3 use the longer or shorter plugs? OR is it safe to run either and the shorter MR43T are MEANT to be shorter in that motor? (or is there a longer copper plug that crosses over to the 41-932 platinum plugs?)

 

[alldodge]

The short plug (MR43T) are in non-vortec motors, the longer plug (MR43LTS) is used in vortec motors. Its best to not swap the length of the plug in a given motor, and even more so in a EFI one.

If you go to http://www.sparkplugs.com and then enter 41-932 another screen will come up. Select other brands and there will be pic with info

 

[USA_boater]

Okay thanks...in the video what it looks like is perhaps someone used the vortec plugs in a non-vortec motor since the electrode had broke off!

 

[billbayliner]

Little story... My favorite boat... Bayliner 1950... Had the wrong plugs in for 15 years.... Always ran perfect, but was rough on start up.... Then smoothed out.... I am one that is BY THE BOOK. Engineers get paid allot of money to make wise decisions.

When I replaced the plugs over the years I matched them to the part number already in the engine....

Fast forward to this spring.... Had to pull the distributor to replace the pick up coil and went into the manual for the bypass procedure for setting timing for the 3.0 LX engine... NOTICED a star beside the 3,0 LX.... I had the wrong plugs in for all these years...

Local shop had put the wrong plugs in and I followed the trend...

Go to the Volvo. / Mercruiser site and get the proper part number and let them do the decisions for you.

 

[USA_boater]

Little story... My favorite boat... Bayliner 1950... Had the wrong plugs in for 15 years....
Local shop had put the wrong plugs in
/QUOTE]

I get sick of other people letting me down. Whether it is a fast food joint or a repair shop, nobody cares anymore and they are never accountable. Due to similar experiences as you, I EXPECT this type of thing in any interaction I have now a days and that is why I do my best to do it myself if I can. I admit it was a lot easier when I was younger and had no kids...it is hard to do-it-yourself when you have very limited time/energy but otherwise, you have about a 50/50 change in 2018 that you'll get the wrong plugs LOL!