83 johnson 8hp help

[lou_b_83]

Hello all
Looking for a little help. I am new to the outboard world. I got my motor from a guy about 3 weeks ago. He ran it in his tank and seemed fine. He said he runs it at 50:1 even thought it says 100:1 on it. I did the same but it is not running right. It idles fine and runs fine in the lower rpms but it will not run in the higher rpms. It boggs down bad. I am not new to the 2 stroke world so I played with it a little but same thing.

First question- can some one tell me what the 4 diffent screws do. I think that the lower right one is idle speed. Lower left is carb adjustment. but I dont understand what the top 2 do.

number 2 - whats wrong with my motor.

Thanks for your help

 

[nwcove]

Re: 83 johnson 8hp help

i dont think they made an 8 hp in 1983, but the only two adjustments you should have is the small idle speed screw, and the lean/rich needle that comes out the front of the lower cowl.
are you sure its running on two cyls? ( replace plugs first then if no change , check coils)
also could need a good carb cleaning and kit.

 

[lou_b_83]

Re: 83 johnson 8hp help

sorry for the total newb question

There are only 2 things sticking out the front. Pull handle and the choke. Is the black handle in front a choke or is it more? I need a owners manual. lol :facepalm:

I did check the plug. They are firing but I will get new to be sure.

I will goggle the model # to check the year and plug gap. Thanks for the heads up.

 

[Davem3]

Re: 83 johnson 8hp help

1983 Johnson 2-STROKE Series 8RCT..........

okay, there should be 3 things in the front, Starter cord, Choke and slow speed knob. the slow speed knob is probably missing.

do NOT mess with it at all, the reason i say this is because you say it idles fine, it controls that.

use champion spark plug QL77JC4 only. for some reason Johnson's like champion spark plugs and hate everything else..........

i seriously doubt it is the powerpack, they either usually run or not at all, no inbetween...... but i could be wrong (according to my wife, ALWAYS!)

i am looking at the carb right now, and only see 2 screws, one is the idle screw and the low speed idle screw............

out of the gate, try this..............

A) only run 50:1 mixture, PERIOD!

B) try mixing Seafoam in with the gas, and completely decarbonize the engine, blow out the cylinders, and blow it through the carb........

C) if this does not do the trick, the plate under the flywheel is controlled by the throttle, and can be out of adjustment, one thing to look at ............ and investigate

D) and this you will hate, trust me............ rebuild the carb, kit is easy to get, job is a PITA.............use a workbench that is totally clean and free of ANYTHING, and go slowly through it

kit can be found and ordered here : http://www.marineengine.com/parts/j...&manufacturer=Evinrude&section=Carburetor-7.5

finally the files for decarbing the motor and much much more can be had here in the secret files section here:

http://forums.iboats.com/showthread.php?t=299680

let me know how it goes, please.............

Dave

P.S. i KNOW it is a 8 HP engine, for some reason it is listed as a 7.5

tomato, tomatoe ............. blah blah blah bleeping engineers:facepalm:

 

[lou_b_83]

Re: 83 johnson 8hp help

nothing to see

 

[lou_b_83]

Re: 83 johnson 8hp help

ok google god said it is an 1986 not a 83. Mod # J8RCDE. Sorry about that.
Here are some pics. First one is under the hood so you can see the 4 screews. Bottom 2 sceews are flat heads in green. The top 2 are 7/32 alen keys in red. The top 2 seem to fight each other. One pushs the throttle wheel (I have know clue what it is called) the other spaces out the piece of plastic the wheel roles on. But I can't realy figure out how they work with each other. After some more tinkering I got it so i can go at 1/2 throttle smooth running but still bogs at full.

Of the front of it. Just 2 things sticking out. No extra holes. Please help

 

[lou_b_83]

Re: 83 johnson 8hp help

OK here is a kick in the pants. I was looking at the carb diagram on the johnson website and the do not show 4 screews. They do not list the lower left screew with the spring. GRRRR. I realy dont want to spend money on a supid fix.:facepalm:

 

[lou_b_83]

Re: 83 johnson 8hp help

I think it is a 1988 carb. Is there a way to tell? Thanks again

 

[Davem3]

Re: 83 johnson 8hp help

okay, post 4 still stands with a major fubar exception, there is no low speed idle screw going out front anymore............ let me do some more research, will get back to you, lou...............

updated parts list here :http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1986&hp=8&model=J8RCDE

updated carb rebuild kit here, still leaning in this direction, thinking the high speed jet is clogged up and bogging you down .................

http://www.marineengine.com/parts/j...8RCDE&manufacturer=Johnson&section=Carburetor

run that part number on the top of your carb, the cover and see where it lands, that will remove all doubt what year the carb is

 

[lou_b_83]

Re: 83 johnson 8hp help

Thanks for all the info. Do you think it would be worth just trying a little carb cleaner befor the rebuild or is that a boat motor no no?

 

[lou_b_83]

Re: 83 johnson 8hp help

Last dumb question (I hope)

What do the 2 screws I circled in red do? It seem the one on the right controls throttling up the carb and the other makes it work with the handle but why have adjustments on them let alone 2 .?.?

 

[lou_b_83]

Re: 83 johnson 8hp help

New symptom to think on.
At full throttle it sounds like I am hitting a rev limiter and then dies out.

 

[AEROCOOK]

Re: 83 johnson 8hp help

sorry for the total newb question

There are only 2 things sticking out the front. Pull handle and the choke. Is the black handle in front a choke or is it more? I need a owners manual. lol :facepalm:

I did check the plug. They are firing but I will get new to be sure.

I will goggle the model # to check the year and plug gap. Thanks for the heads up.

The knob sticking out the front is both a primer and a choke. When you pull it all the way out and let it go and it will spring back in, this is the primer function. When fuel is in the lines and you pull it out a few times, you should feel some resistance as the primer is injecting fuel into the intake. After priming just let the knob go (dont push it back in) and a red ring at the base of the shaft should be visible, this is the choke position. After the motor has started up and is running smoothly, push the knob all the way in, the choke is now off and you are good to go. As for identifying the carb, if it's had the updated plastic top installed it will look different than the one in the manual or the catalog as the needle jet will be in a totally different spot. A lot of these motors have been updated over the years, (mine included) as the original ones were prone to breakage at the roller wheel post.

 

[AEROCOOK]

Re: 83 johnson 8hp help

I just had a look at my carb for comparison purposes it's the same as yours so that means you have the updated top with the relocated needle. With the carb silencer on you wont be able to get a screwdriver onto the relocated screw so drill a hole through the silencer like in the picture you will be able to do the required adjustment.

 

[lou_b_83]

Re: 83 johnson 8hp help

So I think I have got it. Its the damn airbox. I is not seating well to the carb and is letting in to much air. If I close it off with some tap the motor runs great. can one of you guys take a pic of your air box for me. i have a feeling that this one does not belong. Also is there a place that I can get one? I looked a bit and it looks like they dont make them anymore.

 

[AEROCOOK]

Re: 83 johnson 8hp help

Here are some pix of my 1987 8hp.

 

[Davem3]

Re: 83 johnson 8hp help

Thanks for all the info. Do you think it would be worth just trying a little carb cleaner befor the rebuild or is that a boat motor no no?

carb cleaner big boo boo.............it will eat up all the oil in the cylinder, a major mistake, you need that oil in there, hence gas/oil mix............... seafoam only

 

[Davem3]

Re: 83 johnson 8hp help

So I think I have got it. Its the damn airbox. I is not seating well to the carb and is letting in to much air. If I close it off with some tap the motor runs great. can one of you guys take a pic of your air box for me. i have a feeling that this one does not belong. Also is there a place that I can get one? I looked a bit and it looks like they dont make them anymore.

maybe get rid of it entirely ????? my 1968 does not have one?????

 

[nwcove]

Re: 83 johnson 8hp help

the airbox isnt a necessary part, its only there to quiet the motor. it in no way meters air to the engine.