Johnson 9.5

[harleylarry]

I have a 1971 Johnson 9.5 that starts and runs great untill you get about half throttle and then it will die down like its out of gas. once you slow it down it will run perfect. I replaced all the fuel lines. Does anyone know what the problem might be?

 

[jbjennings]

Re: Johnson 9.5

You've replaced the line from the tank to the motor? Have you the hose that goes from the fuel pump to the carb loose from the carb and pulled it a few turns to see if the fuel pump is pumping good pulses of fuel out? Have you tried seeing if pumping the primer bulb forces fuel out of the line at the end (maybe the primer bulb check valve is bad or a faulty fuel tank pickup tube).
You also might take the fuel line loose at the carb and pump the primer bulb just to see if that gives you any hint at a restriction in the lines or connections.
It's got to be some kind of fuel restriction to do as you describe.
Lastly, it could be something as easy as a misadjusted float arm.
Does it start back up after dying when you give it wide open throttle and it dies? If not and it takes several pulls, it could be a pinhole in your fuel pump diaphram allowing fuel to flood the cylinders.
Have you tried pumping the primer when you give it gas? If you pump the primer and it runs great wide open then it's a good chance it may be your fuel pump.
Any extra info. would be great, as it could be a number of things.
Hope you find it,
JBJ

 

[harleylarry]

Re: Johnson 9.5

I replaced the hose from the tank to the fuel pump and from the pump to the carb. I didn't replace the bulb. I've tried pumping the bulb and that doesn't help. It does take a few pulls to start it after it has died. Thanks for the help!

 

[tashasdaddy]

Re: Johnson 9.5

could be a clogged high speed jet, or miss adjusted jet.

(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.

 

[Mandrake35]

Re: Johnson 9.5

I just got through changing my fuel lines on top of a pot pourri of other long neglected parts. I got a carb kit for mine, which came with among other things....a new screen for the fuel pump assembly. You wouldn't believe the junk that was in there.......sand, seeds, pine needles.....gunk. This is one easy area to check, and might cause the lack of power you describe.

 

[Rick.]

Re: Johnson 9.5

Mandrake35. I just put a new carb. kit in my 73 9.5 over the lunch hour today. It came with a new float, needle and seat and a bunch ov other gaskets and stuff. It came with a new screen, very fine with four holes stamped in it and a matching cork gasket. Mine had nothing like that so I assumed they are for a different carb. I never got a new fuel filter gasket though. Ezeke told me the new kit would come with a revision which now clips the needle to the float.( like most carbs.) The new float is still cork and I was thinking it would be plastic.

 

[KCKracker]

Re: Johnson 9.5

i had same symptoms last year, fooled us bad, til we figured out we did our math wrong, we were mixing way too much oil. seems way to simple but died at half throttle or sputtered.

 

[harleylarry]

Re: Johnson 9.5

I took the hose and tank off my other boat and ran it today and still had the same problem. Took the fuel line off carb and pumped bulb and got plenty of fuel out of the pump. Guess I will have to look at the carb! Thanks for all the help!

 

[Mandrake35]

Re: Johnson 9.5

Hey Larry! Its possible our motors have slight differences, mine is a 1965 evinrude 9.5. I'm pretty sure you also have a fixed high speed jet on your carb....it's accessed via the screw under your float bowl. Mine was pristine, however I've read on here that it being gummed up could cause problems similar to what you are encountering. When you squeeze your bulb you say there is no difference as its dying out??? If that is the case....I'd look to your float being misadjusted, maybe even poor spark. Do you smell gas when it dies out? Have you tried running it with the cover off? Apparently our motors are succeptible to exhaust choking out the engine....though I would think that would stop it from running well at low speed also. When you say it runs well at low speed......does that mean it runs like a top? or just runs? Keep updating......I'm anxious to see what you find. Take care Drake

 

[Mas]

Re: Johnson 9.5

How about spark and compression? Although the carb is you likely problem, you may just try pulling one plug at a time to see if any changes occur while its running...if no change in rpm occur, you may have another problem.

MAS

 

[Woodstock60]

Re: Johnson 9.5

0 It came with a new screen, very fine with four holes stamped in it and a matching cork gasket. Mine had nothing like that so I assumed they are for a different carb. .

Rick that is the fuel filter screen that goes on the fuel pump. some models have that. Ronnie

 

[jbjennings]

Re: Johnson 9.5

Mandrake brought up a good point---try running it with the cover off. It may have a leaking exhaust gasket which lots of folks with a 9.5 have trouble with.
Later,
JBJ

 

[harleylarry]

Re: Johnson 9.5

Put a carb kit in it today and now it runs great! I think the problem was the float! Put the new screen in fuel pump also, it didn't even have one! Thanks for all the help!!!!!!!

 

[Mandrake35]

Re: Johnson 9.5

Glad everything worked out for you Larry happy trolling