Spark plugs for 1990 90HP Johnson

[ineedacottage]

Hey guys,

I am looking for a little clarification on plugs and what they should be gapped to.

Model #: CJ90TLCEM

Manual states QL77JC4 gapped at .030"

I have seen references on the site here by Joe Reeves to set the gap to .040".

Which is better? I have no idea what the current plugs are gapped to and I have not changed mine before (I have owned the boat/motor since 1999 - bought from the original owner) - I did not realize that the plugs should be changed yearly.

I also saw reference to using a different plug - QL82C? Are these better?

Also, I have not had it out this year yet (unfortunately too busy), but I am taking it out this weekend finally - should I run the motor with the existing spark plugs and stablized gas before putting the new plugs in to clear the fogging oil from winterizing or change them before even firing her up for the first time this spring?

Thanks a bunch for your help!

 

[tashasdaddy]

Re: Spark plugs for 1990 90HP Johnson

run your old plugs first, my OEM manual states, recommended QL77JC4 gapped .040, sustained high speed running QUL77V which is a fixed surface plug. wot should be between 4500-5500, horsepower rated at 5000.

 

[ineedacottage]

Re: Spark plugs for 1990 90HP Johnson

run your old plugs first, my OEM manual states, recommended QL77JC4 gapped .040, sustained high speed running QUL77V which is a fixed surface plug. wot should be between 4500-5500, horsepower rated at 5000.

Thanks tashasdaddy! At least our manuals agree on which plugs to use. I will gap them at .040".

Now I need to find out why my tach is not working...it was behaving funny last season. I checked the battery with a multimeter and voltage was normal...at idle and at speed.

Thanks again!

 

[Silvertip]

Re: Spark plugs for 1990 90HP Johnson

Depending on operating conditions, there is no "rule" that says you should change plugs every year. It is however, a good practice. If you only put a few hours each season on the engine there is no need to change them. However, they should at least be checked at the beginning of each season.

 

[ineedacottage]

Re: Spark plugs for 1990 90HP Johnson

Depending on operating conditions, there is no "rule" that says you should change plugs every year. It is however, a good practice. If you only put a few hours each season on the engine there is no need to change them. However, they should at least be checked at the beginning of each season.

What exactly should I be checking for?

For about 2 or 3 of the seasons that I have owned the motor I used it about every other weekend on average. The remaining seasons have been every weekend. This is from beginning of June until mid September. I use it for wakeboarding, skiing, kneeboarding, tubing etc. When I am at the lake she goes pretty steady from 11:00 am to 7:00. The last couple of years have been a little more laid back in the use of the boat (I have a 1-1/2 year old and a 3-1/2 year old; they like the play structures at the beach too )

I assume from that usage that I should be changing the plugs yearly - but I am new to doing maintenance myself so I am far from an expert and any and all advice from the experts and more knowledgeable posters here is extremely welcome! I love my boat and I want to use it for many more years!! She has been very reliable to me and I want to keep it that way!

Oh, and I wish I had a longer boating season up here in Manitoba!

Thanks for all your help!!

 

[rickdb1boat]

Re: Spark plugs for 1990 90HP Johnson

Keep it simple and change them every spring....