Spark Plugs

Texascuda · **Joined:** Tue Sep 10, 2013 10:35 am **Posts:** 10

Greetings from DFW, I've been reading the forum and looking for some advice (did search the forum). I've worked on cars for quite a while but boats are a little new to me and just picked up a 1999 Four Winns H200. My question is, I'm doing a tune-up, took out the old spark plugs, and they were MR43T, after reading the posts, not sure which is the right plug to use.
1999 5.0 GL PWTR
The plugs I bought were RS12YC and there's quite a bit of difference in threaded length.

Regards and looking forward to your answers.

fiznuka · **Posted:** Sun Sep 15, 2013 7:00 pm

Take the ones you bought-back and get the MR43T.

Texascuda · **Joined:** Tue Sep 10, 2013 10:35 am **Posts:** 10

Ok thanks but should I have the longer threaded plugs like mr43tls, I think this motor is non vortec heads as it has 6 intake bolts for each side of the head.

Regards

rpengr · **Posted:** Sun Sep 15, 2013 9:58 pm

Just for refference, RS12YC is what I had in my 2000 5.7GS with Vortec heads

ric · **Posted:** Sun Sep 15, 2013 10:13 pm

Iridium plugs with never seize on the threads. Hopefully the last time you'll ever chang em.

Texascuda · **Joined:** Tue Sep 10, 2013 10:35 am **Posts:** 10

So if I;m reading this correctly it should have the long threaded plug?

Regards

1999 FW H200
2005 C6 Corvette
2008 Titan
1970 Plymouth Cuda

rpengr · **Posted:** Mon Sep 16, 2013 10:44 am

Texascuda wrote:

So if I;m reading this correctly it should have the long threaded plug?

I don't want to give you bad advise, but I can tell you that on my Charcoal Grey early 2000 5.7GSPWTR, I have the long thread plugs RS12YC. It is my understanding that I have Vortec Heads. I have 4 bolts on each side of the intake.

Volvo Penta Store shows 1994-2000 charcoal grey 5.0GLPWTR and 5.7GSPWTR to have the same plugs (volvo p/n 3851875)
http://www.volvopentastore.com/Ignition/dm/cart_id.368763004--qty_311029.2--session_id.736463199--store_id.366--view_id.775956--viewcart.long

To be sure, maybe you want to talk to another marina to look up your engine model number.

Photo of my intake manifold:

Photo of my old spark plug:
(probably factory original as one had considerable grey paint on it.

Texascuda · **Joined:** Tue Sep 10, 2013 10:35 am **Posts:** 10

Talked to a local dealer said it should be the longer plug had MR43T in it could this be the low RPM at to end?

Thanks,

rpengr · **Posted:** Mon Sep 16, 2013 11:47 am

Texascuda wrote:

Talked to a local dealer said it should be the longer plug had MR43T in it could this be the low RPM at to end?

Thanks,

Could be. Please let us know how it runs (differently) after the tune up.
Good luck

Ray

Texascuda · **Joined:** Tue Sep 10, 2013 10:35 am **Posts:** 10

Will do hope to go out Thursday.

Regards

Graham R · **Posted:** Mon Sep 16, 2013 4:36 pm

The OEM plugs in my 1999 5.7GSi were RS12YC ( they still had black paint overspray when I changed them in 2002). The replacement plugs, from Volvo Penta in VP boxes were at the time not the same, I guess they swapped around depending on which plug supplier gave them the best deal ! The details are in a post of mine from years ago , that I can't find anymore !

Texascuda · **Joined:** Tue Sep 10, 2013 10:35 am **Posts:** 10

Update, boat came up on rpm great, but then started to drop down on rpm, so I throttle back and then a back fire. Not sure if through the carb or exhaust. Going to get rid of the Champion plug and check the fuel filter. Only thing I changed was from MR43t to the Rs12yc, cap, rotor, fuel filter.

So any other suggest I'm listening.....

1999 FW h200, 5.0GL PWTR

Regards

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

Sounds like a fuel feed issue to me. Check the fuel lines to be sure they're not sucking air. Check the anti-siphon valve to be sure there isn't a bunch of trash caught up in it. Make sure there's no water in the fuel filter and that the fuel filter is freely flowing. Sorry for the accidental alliteration.

rpengr · **Posted:** Fri Sep 20, 2013 6:05 pm

Sounds like a fuel starvation problem to me too. Ran good until the carburetor bowl ran low? Did you pre-fill the fuel filter? (not entirely necessary with a carburated engine). Can you disconnect the fuel line from the carburetor to check for fuel flow? (making sure you capture the fuel to prevent spilled fuel/fumes in your engine compartment)

Does not sound spark plug related at all.

Texascuda · **Joined:** Tue Sep 10, 2013 10:35 am **Posts:** 10

New update: Changed to MR43LTS and no problems, did not like the RS12YC.

Regards

www.iFourWinns.com

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