# 1975 Johnson 6 hp wont run full speed



## FishingRust (May 24, 2010)

Hey everyone when I was out with my brother yesterday I noticed that my motor would only run at about half the speed it normally does (WOT is half normal speed). So I went out alone today with no gear and its doing the same thing any ideas?


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## Quackrstackr (May 24, 2010)

Are you talking seat of the pants or rpm here?

If it is rpm, your high speed jet may be clogged.

I don't know the particulars of the small motors like yours but if it is a twin cylinder, it may also have a cylinder down for some reason. Could be a bad plug or wire.


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## FishingRust (May 24, 2010)

I am talking about rpms how can I clean the jet? It wont go as fast as it used to about half the speed


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## bassboy1 (May 24, 2010)

FishingRust said:


> I am talking about rpms how can I clean the jet?



Full carb rebuild. The rebuild kit doesn't cost much at all, and it is bad practice to disassemble a carb without replacing all the gaskets and the likes upon reassembly. Not to say I haven't done it, but in most cases, it is bad practice. I'm guessing that your motor hasn't had a carb rebuild recently, in which case the gaskets and all will likely be too worn out to reuse.


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## FishingRust (May 24, 2010)

Ok thanks a lot do you know were to get a rebuild? As far as I know it has never had one :shock: but i could be wrong.
Thanks


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## FishingRust (May 24, 2010)

oh and how hard are they to do?


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## cajuncook1 (May 25, 2010)

FishingRust said:


> Hey everyone when I was out with my brother yesterday I noticed that my motor would only run at about half the speed it normally does (WOT is half normal speed). So I went out alone today with no gear and its doing the same thing any ideas?




Try checking to see if you are running on one cylinder.  Those little 6hp motors are tough and will run decent on one cylinder but half the power. 

Spark plugs- (torque to 17 to 20 foot pounds with a torque wrench)
Spark plugs gapped at 0.030 (use a feeler gauge)

Check to see if you have good spark on both cylinders using a spark plug test, not just a spark on the end of the plug. ( Please undo both plugs, so you don't accident start the motor) Should have a good strong spark at 1/4 to 5/16 inch on the spark plugs tester. (ground the tester to the motor). If you have a cylinder that has no spark or very weak then your basically running on one cylinder. Father in-laws Evinrude 6hp motor was running ok and idle a little rough but it was running on one cylinder, no spark on top cylinder and was running about half power. Had to change the coil on the motor and now it runs smooth and he is happy again. These motors are tough and will run on one cylinder but poorer than usual.

Another way to tell if you are running on one cylinder is to start up the motor(in the water) and let her warm up for a minute or two. Carefully unplug the boot to the top plug, if runs rough but maintains some then the bottom plug/connnected cylinder is firing. If it dies then you know that you have a cylinder that is not firing/spark. Replace the top spark plug boot carefully and let a run for a minute or two, then unplug the bottom plug boot, if it dies then you know that you have the top cylinder plug/wire that is not firing/spark. If runs rough but maintains some then the top cylinder is firing.

spark plug tester $7.00
https://www.autozone.com/autozone/catalo ... ctId=10257

feeler guage $7.00
https://www.autozone.com/autozone/catalo ... uctId=1929

torque wrench $21.00
https://www.napaautoparts.com/Search/Det ... 0006395373

*If you have good consistent spark on both cylinders then I would move on the carburetor and possible carb kit.*

Here is a couple of links to help you out with carburetor rebuild.

https://www.sschapterpsa.com/ramblings/OMC_6hp.htm ( You will like this one)

https://forums.iboats.com/showthread.php?t=244013

https://forums.iboats.com/showthread.php?t=167352

**Make sure your vent plug is open plug on your tank open when your running/starting your motor if you have a plastic tank. (You may laugh, but all of us have forgotten to open that vent plug while starting up the motor in the morning for a day of fishing and find a little while later the motor is running like do do, because the air can't entering the tank. The motor's and fuel pump is now trying to suck gas from a tank that has a negative pressure in it. **

Good luck my friend,

cajuncook1


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## FishingRust (May 25, 2010)

Thanks a lot man I was hoping you would say something but a have a question for you when I take off the top spark plug wire it just slows down. But when I take off the bottom one off the motor just dies. Does this mean I have a bad cylinder?


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## FishingRust (May 25, 2010)

I just re read what you said how can I fix the bad top cylinder problem?


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## Quackrstackr (May 25, 2010)

Most likely it is something to do with the plug firing. Change the plug, check the plug wire and the coil.

You can also take it somewhere and have the compression checked on each cylinder. Hopefully something worse that spark issues hasn't happened.


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## cajuncook1 (May 25, 2010)

FishingRust said:


> Thanks a lot man I was hoping you would say something but a have a question for you when I take off the top spark plug wire it just slows down. But when I take off the bottom one off the motor just dies. Does this mean I have a bad cylinder?




Hey FishingRust,

It does not necessarily mean the top cylinder is bad. Chances are that you do not have a spark or very weak spark going to that cylinder.

Things to do:

1 Buy a spark tester, see the link I supplied previously. Check both top and bottom cylinders( even though the problem, as you stated, seems to be coming from the top cylinder. 

2 If there is a good spark on both cylinders, then you should change your spark plugs.

Champion J4J is the Evinrude manual recommendation.
Gap the plugs at 0.030in (That's what the feeler gauge is for)

3. If there is still no spark, then you have to decide if you want to take off the flywheel your self or bring it to a mechanic. Under the flywheel are coils, condensers, and points.

Here is a link telling you how to take off the flywheel and the tools you need.

https://forums.iboats.com/showthread.php?t=338579

Here is a link that talks about the flywheel removal, inspecting/changing the points, coils, and condenser

https://forums.iboats.com/showthread.php?t=294072

Here is great read about your motor by the machinist. (Excellent)

https://www.sschapterpsa.com/ramblings/OMC_6hp.htm

If you join the iboats forum then you can see the pictures with the above links. Don't worry its free just like this site. The only reason I pointed you to those links on that forum, because the reads on those links are excellent and very informative.

I would suggest getting a manual for your motor, so you can maintain her and the manual gives a lot of good information, pictures, and specifications.

Good luck and keep us posted.

cajuncook1


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## FishingRust (May 26, 2010)

Thanks a lot man the links for the tools didn't work. When I leave the top plug in and take off the bottom one it dies what exactly is a feeler gauge? I will probably do the work my self unless it is something extremely hard. Thanks again I will replace the spark plugs and then see what happens.


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## crazymanme2 (May 26, 2010)

Your going to work on your motor & don't know what a feeler gauge is?Its used to measure the gap of the spark plug.
Good luck.


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## FishingRust (May 26, 2010)

Just never knew what they were called


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