Would this be OK? spark plugs

[kodibass]

thanks to Iboats I now know my 1975 40 HP Johnson 40rl 75-c has no T-stat (anyone know why ??) & should have L82-c SPARK PLUGS, it has UL-81C plugs in it right now & came with a brand new set of QL87c plugs I will buy the correct plugs to put in, Was wondering tho would either of these be ok or better than the other as a back up set to throw in the boat. I know diddle about spark plug #'s letters . thanks

 

[gm280]

Re: Would this be OK? spark plugs

Hello again. I think I posted about your engine before. I have a 1976 version of that Johnson 40 HP. Again why those 40's don't have a thermostat is anybody's guess. But it must work okay without one because there are a lot of them out there. The plugs for your engine are listed as L4J according to the IPB (Illustrated Parts Breakdown) on here on iboats at this address;

http://www.**********/parts/search/BRP/JOHNSON/1975/40RL75C/CYLINDER & CRANKCASE/parts.html

You can look up most any part for your engine looking through those IPB’s. The L4J plugs are changed to L82C. I think when I order mine they actually sent the L82C plugs from iboats. Not knowing for certain, the UL-81C may be a little cooler running type plug then the L82C. I’m sure the plug experts on here will explain. But you could keep yours for backup if need be and would work in a pinch if you needed them...

 

[HighTrim]

Re: Would this be OK? spark plugs

Seems to depend on which plug chart you use. I have a few of them. Some say to use the UL 81C like here

http://www.boatsetup.com/Spark Plug Chart 2007 BRP.pdf

Some say the L82C like here

Johnson Cylinder & Crankcase Parts for 1975 40hp 40RL75C Outboard Motor

Just depends on which one works best in your motor.

The difference between the UL 81C and the L82C is that the UL81C is an auxilary gap, and also a touch colder. The "L" means they are both 14mm

The "C" in both stand for copper plus design.

The QL87Cs are similar, but are resistor style compared to the auxilary like the UL81C. It is hotter than the other 2, but same 14mm thread and same copper plus design.

Bottom line is they can all be used. I dont have much experience with that model, so cannot say which one I personally prefer. I would think that Id rather have the L82C or the QL87C as Im not a big fan of the auxilary style for whatever reason.

 

[kodibass]

Re: Would this be OK? spark plugs

Thanks, for the responses good info, I kinda like the fact that it don't have a T-stat... it ends the age old debate as to if its ok to run without one I like the look of this old Johnson So I plan to keep it, It has the largest prop I have ever seen on a 40hp. If all works out I will soon have a commercial grade aluminum welded skiff to put it on.