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johnson 9.5 won't run properly at high speed

E

emoe850

New member
Hello,

I have a 1965 9.5 Johnson Seahorse short shaft motor (MQ11C)

The problem is it does not run properly in the high speed circuit of the carburetor.

From idle up to where it engages the throttle on the cam there is good engine response.

Once in to the high speed circuit the engine can’t get enough air (too much fuel).

I have tried to run at full throttle and after a while stop and look at the plugs and they are soaking wet with fuel.

If I pinch off the fuel feed line and run the fuel out of the carburetor, there is a spot where the Air fuel mix is good and the motor takes off like a bear.

I have checked the carb float, shutoff, mainjet (.048 dia) seem to be good.

The propeller seems to be the correct size, infact it is worn and is smaller in diameter….71/2 or so.

I have replaced the points and condensers, good spark, starts fine.

Over the winter I used some seafoam and got a lot of black goo out of the engine.
 
This may sound crazy, but have you tried to run it without the hood on? You may have an exhaust leak.

I would clean and rebuild the carb, make sure the float is parellel to the bottom surface of the carb body when flipped upside down.

Run the motor with the hood off

Look at the spark advance cam, see if theres a large amount of wear

Usually the problem is not enough fuel, not too much
 
Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle va /lve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway

Ignore the high speed setting as the high speed jet is fixed on 9.5's
 
(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store
 
Thank you all,
It was the point timing that was the problem. once I set the points to break at the correct time the motor runs like it should.
Thanks again
 
For future reference:

(Point Setting Of Magneto Models)
(J. Reeves)


Set the points as follows. Have the flywheel key aligned with the fiber rubber portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

NOTE: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.
Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:
http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

Curious as to how those points got set so wrong in the first place.
 
joe reeves,

How I found this is I detuned the carb until the motor ran reasonable. in other words as the cam opens the carb I set it so it wouldn't open so far at full throttle. This made the motor run better. At that point I realized that the timing was probably off and I wasn't getting the advance in spark that i needed. So instead of setting the points to .020, I set them so that they just break open when the timing mark on the fly wheel says they should be open (you need a meter or a light). There is a mark for both sets of points on the fly wheel and the points plate that need to line up when the points just break open. It takes some time to get it right. I didn't measure the gap but i'm sure it isn't .020. I have worked on a lot of motors and set a lot of points, I have never used this method. I have read about it in many manuals but never used it. By timing this engine this way kept me from tossing this motor.
 
I'm aware of what you speak of. We had special tools that we could acurately set points with, but the .020/.022 method gets the timing so close that it can be considered exact.

I'd be interested in knowing what setting you came up with. The flywheel key must be aligned with the fiber rubbing portion of the points to check the gap.
 
farnsp said:
This may sound crazy, but have you tried to run it without the hood on? You may have an exhaust leak.

I would clean and rebuild the carb, make sure the float is parellel to the bottom surface of the carb body when flipped upside down.

Run the motor with the hood off

Look at the spark advance cam, see if theres a large amount of wear

Usually the problem is not enough fuel, not too much
Click to expand...
I just bought a 1965 9.5 Evinrude that has had some new parts put in , fuel pump , coil points , carb rebuilt. Now when i run it i'm having that problem, runs like crap with the hood on and when i take it off runs great !!! How come ???
 
joereeves said:
This post is over 3 years old. I suspect that all is well by now.
Click to expand...

Yes i know it's an old , old ,old post but i was reading what the guy said about running it with the hood/cover off. So that is what i would like to know how can the exhaust get into the hood compartment and make it run so bad ? The other thing is i just purchased this motor two days ago !
 
There is a rubber tube that runs from the back of the powerhead to the outside of the lower cowl that is a exhaust outlet that leaks, not letting your motor get fresh air.
 
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