Spark plug recommendation for Johnson 50 hp motor?

[jpmobydick]

I know I should be able to find this on my own but the question is complicated. I have what I think is a 1990 VRO Johnson outboard or at least that is what I thought I bought and cowl indicates that. In looking up serial number I could not find the plate any where and the serial number on bill of sale does not jive with internet info. I read where there is a round plug on the head that gives the serial number. Sure enough number iit is there E4QELCDE. This I think tells me that I have a 40 hp evinrude. Is it possible that motor was rebuilt or repaired using Evinrude parts? Do I have a 40 or a 50 hp? Now getting to spark plugs, the ones in the motor now are NGK (R) BR9HS. Are these the right plugs? What would I use if I wanted to use champion plugs? I know it is a lot of questions but would appreciate any help that I can get. Thank you in advance.

 

[jpmobydick]

Re: Spark plug recommendation for Johnson 50 hp motor?

I missed an important fact. The motor was sold to me as a 5o hp motor and that is what the cowling indicates. Some friends have told me that some motors use the same basic construction and simply change the carburation to get additional horsepower. So my confusion lies with with the serial number indicating an evinrude and 40 hp. And does that affect my choice of spark plug choice.

 

[jtexas]

Re: Spark plug recommendation for Johnson 50 hp motor?

you for sure want to run the champion plugs in it -- don't panic, just whenever you get around to it. NGK makes a great plug no doubt, but it'll do better on champs in the long run.

You sure about the "Q"? should be a 0 there. That would make it a 40hp.

Usually (not always) it takes more than carburetor change to upgrade even when it's a common block - cylinder head and intake manifold at least. Access to schematics is free online at www.shop.evinrude.com click on "electronic parts catalogues", select "Johnson" in the drop-down box, drill down to your year/hp/model number. You can compare various part numbers between the 40 & 50 to see the differences.

the spark plug is on the cylinder/crankcase diagram, probably the same for both models

Could be a 40 with a 50 cowling.

Or, if you blew a 40hp powerhead & found a 50hp for a good price, you could probably just bolt it on (I can't say for sure with this particular motor). The mounting bracket (and title too, probably) would still show the 40hp model number.

 

[hidef]

Re: Spark plug recommendation for Johnson 50 hp motor?

The factory recommended plug is Champion QL77. The 40 and 50 used the same basic powerhead. So it is possible you have a 40 block with all of the 50 parts attached to it making it a 50.

 

[jpmobydick]

Re: Spark plug recommendation for Johnson 50 hp motor?

Thank you both so very much. I went to the sight that you referred me to jtexas and found exactly what you said hidef. Just wondered if either of you could comment on something for me.
1. Hidef you indicated to use QL77 and the site said L77 is ok as well. I went to store and found both. What is the difference? Is there an operational advantage?

2. The site jtexas referred me to also indicated that if you were doing "Sustained Full Throttle Operation" use Champion L-78V and also in this plug line a QL-78V is available. Again that infamous "Q" and in each case higher cost. My question is what is the difference of this plug from the L77 and is there value to go to it or to the "Q" prefexed plug.

Once again thanks so much for your help and the terrific quotes.

PS I checked and it is not a Q in the serial number. It is a 0 as you thought it should be.

 

[hidef]

Re: Spark plug recommendation for Johnson 50 hp motor?

Q stands for quiet. They have a resistor in them to make them less noisy so they don't interfere with electronics such as radios. You can use either they both function the same.

The V on the end is for surface gap. The work great for WOT lousy for trolling the foul up very easily at low speeds. Stick with the regular L77/QL77 and you will be fine. Gap the plugs .030.

 

[jtexas]

Re: Spark plug recommendation for Johnson 50 hp motor?

I didn't notice this before, but the 1st "E" in your model number means "Evinrude", Johnson model numbers begin with "J". That's no matter, they're interchangeable part for part, but it does add some to the the mystery. What color is the midsection & lower unit?. Does it match the cowl?

The "Q" in champion spark plugs indicates "radio frequency interference suppression". It's a feature added by champion, probably after your motor was built (not sure when). Marine ignitions reportedly are prone to random misfires without this type of plug. I think, if your motor runs good with regular champs, no problem.

The 78 is a surface gap plug with a cooler heat range than the 77. Unless you're running flat out virtually all the time, those plugs will foul more rapidly as the tip might not get hot enough to burn off the carbon deposits.

 

[jpmobydick]

Re: Spark plug recommendation for Johnson 50 hp motor?

Thanks for the explanation on the difference in the plugs. Hate to go a day without learning something new.

As for the mystery Evinrude serial number and Johnson housing, all exterior colours are matching Johnson beige. Doesn't look like any mismatching there. I did have an electronic problem a year ago and had to replace a module. The repair guy was a retired OMC fella who worked part time for a shop. He got all the odds and ends and older stuff. It was a weekend and no parts available but he got a 40 hp module from his basement that he said was interchangeable between a 40 and 50. And as I recall he, didn't mention any serial number discrepancy although he said it was in good shape. I can't imagine how much other stuff he has packed away. Chatting with the shop owner, he indicated this fella probably had more parts in stock in house than shop owner had at his business. Some guys just love their work.

Can't complain, the motor runs great and gets me to the fish fast enough.

Once again thanks to both of you.