Carver Owners Forum

mr 44 plug is the next hotter than a mr43
nkg the 6 is the same as a mr43 and a 5 will be hotter

examples

NGK indicates the heat range in the middle of the plug number. For example, BCPR6ES-11 has a heat range of 6. (The number after the “-“ is the Gap.) NGK plugs are colder the higher the number, hotter the lower the number.

Starting with part # BKR6E-11 (Heat Range 6), a colder plug would # BKR7E-11 (Heat Range 7), a hotter plug would be # BKR5E-11 (Heat Range 5).

Autolite:

Autolite indicates the Heat Range with the last digit of the part number. For example, 3923 has a Heat Range of 3. The higher the number, the hotter the plug. The lower the number, the colder the plug.

For example, starting with part # 24 (Heat Range 4), If you want a colder plug you would use part # 23 (Heat Range 3), for a hotter plug you would use part # 25 (Heat Range 5).



Bosch:

Bosch indicates the Heat Range in the middle of the plug number. For example, FR6DC+ has a Heat Range of 6. Bosch plugs get hotter the higher the number, colder the lower the number.

Starting with part # FR6DC+ (Heat Range 6), a colder plug would be # FR5DC+ (Heat Range 5), a hotter plug would be # FR7DC+ (Heat Range 7).



Champion:

Champion indicates the heat range in the middle of the plug number. For example, RV15YC6 has a heat range of 15. (The 6 at the end of this part indicates the Gap setting.) Champion plugs are hotter the higher the number, colder the lower the number.

Starting with part # RCJ7Y (Heat Range 7), a colder plug would be # RCJ6Y (heat range 6), a hotter plug would be # RCJ8Y (Heat Range 8).



Denso:

Denso indicates the heat range in the middle of the plug number. For example, SK20PR-A11 has a heat range of 20. The number at the end of the part indicates the Gap.

Denso Iridium Power plugs feature the Heat Range at the end of the part number. For example, IK20 has a Heat Range of 20. Denso plugs get colder the higher the number, hotter the lower the number. Starting with part # IK20 (Heat Range 20), a colder plug would be # IK22, a hotter plug would be # IK16.

Thank you...great explanation...!

Ok...here's one more question. Today I was at the boat doing a few odds and ends. I happened to look at the placard on the engine that lists the type plugs and the gap etc. The placard calls for a NGK BR6FVX platinum spark plug gapped at .035. Is there a difference in what I am using?

Thanks

Here's how to decipher the nkg plug code. The s is a standard and a vx is platinum tip
NGK SPARKPLUG CODES

The breakdown is like this: [B] [CPR] [6] [E] [S] - [11]
Six fields. Some, e.g. the second field, are optional.
Some fields may have multiple letters.

Field one: Thread diameter.
A = 18mm B = 14mm C = 10mm D = 12mm

Field two: Construction.
C = hex size 5/8" K = hex size 5/8 with projected tip (ISO)
M = compact type P = projected insulator type
R = resistor SD = surface discharge for rotary engines
U = semi-surface discharge Z = inductive suppressor

Field three: Heat Range.
2 = hot, up to 10 = cold. There's no 1, I guess.

Field four: Thread reach.
E = 19mm F = tapered seat
H = 12.7mm (1.5") L = 11.2mm (7/16")

If this field is blank, an 18mm diameter plug has 12mm reach,
and a 14mm plug has a 9.5mm (3/8") reach.

Field Five: Firing end construction.
A, B = special design (no details given)
C = special ground electrode
G = racing use
GV = racing use V type
H = half thread
K = 2 ground electrodes for certain Toyotas
L = half heat range
LM = compact lawn mower type
M = 2 ground electrodes for Mazda rotary engine
N = special ground electrode
P = platinum tip (premium)
Q = 4 ground electrodes
R = delta ground electrode for BMW
S = standard 2.6mm centre electrode
T = 3 ground electrodes
V = fine-wire centre electrode, gold palladium
VX = platinum tip (high performance)
W = tungsten electrode
X = booster gap
Y = v-groove centre electrode

Field Six: (after the dash) Wide gap.
8 = .032" 9 = .036" 10 = .040"
11 = .044" there is no 12 13 = .050"
14 = .055" 15 = .060" 20 = .080"

Gee...you have spent a lot of time educating me about spark plugs. Seriously, I really appreciate the time that you have put into this. Thank you.

Without more info - this to me sounds like the classic "lugging" rattle from a low rpm. I moved a '99 33 SeaRay for a customer last fall from Parry Sound to Port Severn and it had that same "rattle". Bump the throttles up an extra 100 rpm and it was gone.

Thanks, as soon as it warms up a little here in Tennessee I'm going take a closer look, concentrating on idle RPM and when exactly it makes the noise.

Thank you

Check the spark arresters, are the screens clean? Carpet fibers find their way to them and clog them up. I would only put the plugs in that engine that was listed on the plate if it was me. Clean the Throttle bodies. Mike

Well...now there is more to it which might not be so good. Today I installed the new plugs and started up. I went outside and took a good look at the exhaust...actually I was listening to it to see if it sounded somewhat even...probably a worthless endeavor. However I noticed what appeared to be steam (or smoke, I suppose) was coming out of the exhaust and a film of either gas or oil on the water. Hopefully, it's gas. To compound it, I started the other engine and took a look at it's exhaust. There is only water coming out...no smoke (or steam) or oil (or gas).

All kind of things come to mind. So, the transmission is rattling at idle, there is something coming out of the exhaust (smoke or steam). There is a oil sheen on the water. Our mechanic looked at it and thinks it's fuel which would explain the rich looking plugs.

Compression check is next....more to follow.

Don't want to cause undo concern but this is a post I listed before I bought my 1998 Carver.

"Postby Dewmyster » Sun Apr 10, 2016 5:26 pm
Tom, I have a 1998 370 Voyager I purchased last October. 7.4 MPI's with 650 hrs. I backed out of the deal because of the "chatter" from the tranny. Owner had his tech look at it and he spent $7K to make it right. Nothing wrong with the tranny but the port engine needed new heads, manifolds and risers! Rough running engine will cause this. Re-sea trailed and bought it. Love the boat but only used it for 3 weeks and put it away for the winter. Hope to have her in the water for May 1st! Good luck but please do yourself a favor and follow Viper's suggestion related to a Merc Tech."