Wrong spark plugs?

Jeremy90bay · Aug 6, 2009

I think im running the wrong spark plugs? I have not looked in the book until today. I went to westmarine and forgot the plug numbers off my plugs so I looked in the book. the number that came up for my motor was the plugs that dont have the little piece on bottom, the plugs I have in it do. I have never looked up plugs for this before just took the number off the old ones.the boat runs but could this be right?

john from md · Aug 6, 2009

Re: Wrong spark plugs?

Most larger Force engines use surface gap performance plugs. There is no direct replacement for the extended electrode plug and you will burn a hole in a piston if you try using them.

John

Jeremy90bay · Aug 6, 2009

Re: Wrong spark plugs?

Thanks john so let me make sure I understand you right. I should still use the plugs I have been using. NOT the surface ones like the book says. its a 1990 50hp 507x90d

foodfisher · Aug 6, 2009

Re: Wrong spark plugs?

Most of these wise old addicts say, follow the book/manual.

Jeremy90bay · Aug 6, 2009

Re: Wrong spark plugs?

John scared me with burning a hole in the piston but im not sure which plug he said I would do it with.

john from md · Aug 6, 2009

Re: Wrong spark plugs?

Since I don't know what engine you have, I can't look up the plug numbers.

Let me know the engine size and year.

John

Jeremy90bay · Aug 6, 2009

Re: Wrong spark plugs?

Sorry John I thought I put it up there. its a 1990 force 50HP #507X90D. Thanks for your help.

Frank Acampora · Aug 6, 2009

Re: Wrong spark plugs?

Jeremy: The factory has no vested interest in recommending a specific plug and a lot of high priced engineers decided upon the correct plug aftyer numerous running tests. They don't just pull these numbers out of the air. We are not racing applications and you should stay with the recommended plug which is a surface gap plug.

Surface gap plugs are very cold because the insulation is completely encased by the steel shell and cooled by the engine head. They tend to foul a bit easier than bent electrode plugs. Bent electrode plugs have more of the insulation exposed to the heat of combustion and therefore run hotter. There are some on the forum who use the hotter bent electrode plugs to help this condition with no apparent long term problems. BUT: Any bent electrode plug is much hotter than the surface gap and I have seen engines with holes melted in the pistons due to use of these plugs. WHY TAKE A CHANCE?

If I were you, I would remove the bent electrode plugs you now have in the engine and replace them with the surface gap plugs recommended.

john from md · Aug 6, 2009

Re: Wrong spark plugs?

Jeremy,

Now you done it, you incurred the wrath of Frank.

Say three our fathers and three hail marys and put Champion UL18V surface gap plugs in your engine and all will be forgiven.

BTW, don't bother with NGK. I have run them both and for Force applications, the Champion fouls less.

Regards,

John

Jeremy90bay · Aug 6, 2009

Re: Wrong spark plugs?

Thank you very much frank. I will do this right away. Thanks for everybodys help in answering my question. it kind of freaked me out when I went to the store. BTW could this cause any performance issues at all? just wondering.

john from md · Aug 6, 2009

Re: Wrong spark plugs?

Why don't you start a new thread with the problem you are having.

John

Jeremy90bay · Aug 6, 2009

Re: Wrong spark plugs?

I would start a new thread but I dont think I have a problem other than an older 50hp on to heavy of a boat. I would also like to do a few things like a decarb and adjust the carbs before I start getting to many ideas in my head. actually thats a good thread to start. how to adjust my carbs? Thanks john

john from md · Aug 7, 2009

Re: Wrong spark plugs?

Go to the FAQ at the beginning of the Iboats maintenance forums. It is toward the back on the second page I believe. That thread will tell you all you need to know.

John

Jeremy90bay · Aug 8, 2009

Re: Wrong spark plugs?

Ok so I changed the plugs to the correct UL18V plyugs and took it on the lake. it ran great. there is alittle smoke at start but that is to be expected from a 2stroke. correct? the question I have is when I would shut it down so the kids could jump in and swim it was hard to start back up but eventually would with alittle throttle. heres the catch, when I came out of the water I noticed that I never opened the vent on the tank :redface: could this cause this problem. Im thinking it did. what do you think?

john from md · Aug 8, 2009

Re: Wrong spark plugs?

I'm surprised that it even ran with the vent closed!!!

As to starting after shutdown, you sometimes have to give it a little throttle but not all the way up like you would on first start of the day. Whatever you do, don't choke it when it is warm as they flood easily.

John

Jeremy90bay · Aug 8, 2009

Re: Wrong spark plugs?

I usually never habe to give it throttle on first start, is that normal or should I be doing it just to get fast idle?

john from md · Aug 9, 2009

Re: Wrong spark plugs?

The fast idle position is for cold starting. It keeps the engine reving high enough to keep it from fouling during the warm up period.

Have you decarbed your engine recently? Decarbing never hurts and most of the time improves performance. Some engines need more than others.

John

Jeremy90bay · Aug 9, 2009

Re: Wrong spark plugs?

How do I get it to fast idle. I know that you pull the handle out and can move it forward and backward. but where is the correct fast idle speed.

As for decarb I have not yet I planned on doing it while I was on vacation in a week or so. I bought the spray can for decarbing. is this good?

john from md · Aug 9, 2009

Re: Wrong spark plugs?

You pull out the handle and push it forward. Your rpm is limited as there is a mechanical stop that only allows it to go so far. Your fast idle speed should be 1800 to 2000 rpm.

The best way to do a decarb is with seafoam mixed with the gas. The spray cans never did too much for me.

John

Wrong spark plugs?

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