Johnson 9.5 intake air

I bought an old boat to re-do last winter and have a question about the intake air path on the motor. It's a 1965 9.5 Johnson. I had the boat on the lake last weekend and the motor didn't run out 100% so right now it's on a stand and water barrel. The motor appears to be low hours and it looks like someone did some maintenance fairly recently. The spark plug wires are in great shape, plugs look good but dry like it has set for a while, and the carb & fuel pump are shiny and clean like someone rebuilt them. On the lake I thought it was running rich and was hard to start so that's why I put it on the stand. I had to change the low speed mix linkage because the way it was indexed wouldn't let it smooth out at low speeds, was too rich. It runs pretty good now except I think it's still too rich on the top end because it doesn't seem to get to the RPM I think it should. Also when I put the motor cover on it makes the problem considerably worse. The foam in the motor cover is secure and nothing seems to be restricting the air flow.

Questions:
Is the combustion air drawn only from behind the front plate where the start rope, choke, and kill are mounted?

No air filter? Just the plastic screen over the top of the carb?

Is the top end mixture screw the little shaft and screw that runs parallel to the low end mixture screw?

Should there be a big difference in the way it preforms mid and top end when the motor cover is installed and will adjusting the jet compensate for that?

Thanks in advance for any help offered.

Dmilner, you still following this post?

Still following, I work 12 hr shifts so when I'm on duty I pretty much just work and sleep. I think I'll get it to the lake again before I make any more changes. I hadn't run the prop in the barrel but decided the mess might be worth what I would learn. Putting a load on the engine changed everything and it seemed to pull well.

Go to Auto Zone or similar store, they loan out a compression gauge with a deposit. Check your compression on your top and bottom cylinder. Just wanting you make sure you do not have compression issues. You can wrap a pull rope around the flywheel and manual pull until you get your spring starter repaired.

Here is a link to show how to do a compression test. ***Please let me know what the compression value is*** You may have to pull the rope 4 or 5 times to get maximum compression reading and pull on the rope like you mean to start it. Reminder, remove both spark plugs then test one cylinder at a time.

https://www.youtube.com/watch?v=PyCw4SiuT2I

Here is the part number for the carburetor kit for your motor. There is no Sierra or aftermarket kit. Only OMC kit availabel for the this motor.


Carburetor kit part number = 382048

Here is link and parts diagram for your motor and where you can by your parts at a decent price.

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1968&hp=9.5&model=MQ-14D

Here are some carburetor settings.

Carb Needle Adjustments For Asorted Carb Variations by Joe Reeves

these adjustment are for the older engine. 1980 and earlier, and the current small hp ob's. not for fixed jet outboards.


(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently(turn in clockwise), then open 1-1/2 turns(turn out counter clockwise). Do not tighten or force the slow idle needle shut or it may damage the needle.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in (clockwise). Wait a few seconds (10 to 15 sec) for the engine to respond. As you turn the valve in(clockwise), the rpms will increase. Lower the rpms again (turn your throttle slightly slower) 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 (sounds like a mild backfire). At that point, back out(turn out counter clockwise) the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, 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.

Click to expand...

Great info! I'm on duty three days straight so give me a little bit to copy this stuff. I've done a lot of old school small engine work, you've given me pretty much all I i need. Thanks for the help.