How to locate High Speed Jet in carb of 1969 Johnson/Evinrude 9.5 HP

[Calcasieu]

My Johnson 9.5 runs perfectly except at 95-100% throttle. I am experiencing what I think is a little fuel starvation. Quick loss and regain of power intermittently at wide open throttle. It idles perfectly and runs smoothly at all other speeds. I want to specifically clean the high speed jet and was wondering if anyone has a picture of a diagram showing which specific areas I would need to clean to clear up that issue. I recently rebuilt this engine and have cleaned the carb once since rebuilding. I probably have about 7 hours on it since rebuild. Any help is greatly appreciated.

 

[gm280]

First of all, are you sure it is a 1969 Johnson engine? I ask because they don't show a 9.5HP in 1969. They do show a 1968 9.5HP Johnson though. :noidea:

You can go to boats dot net and open up a break down of you engine and carburetor and see how it goes together along with parts list.

 

[racerone]

???--The 9.5 was built from 1964 to 1973.----The high speed jet is found way in behind that hex head drain plug.

 

[Calcasieu]

Thank you racerone!!! I know exactly the spot. I will get working on that. I will report back if it solves the issue.

gm280: the 9.5 was made from 64 to 73 I have rebuilt this entire engine and just want to give a little extra care to the high speed jets when cleaning my carb to alleviate the fuel starvation. The schematics do not label the jets. Just the parts.

 

[racerone]

The high speed jet is also referred to by it's other name.----ORIFICE PLUG--- On parts drawings / blowups.

 

[hardwater fisherman]

High speed orifice plug part number 309681 replaced by part number 0324020. A little spendy though 66 us dollars.

 

[hardwater fisherman]

I had 2 of these motors and sold them to my neighbor to use as parts. He had the same problem with his and it turned out to be the old cork float was too saturated to operate correctly.

 

[Calcasieu]

Thanks for the additional info. The cork is new and still has its clear coating. I sprayed the bejesus out of the high speed jet through the drain plug as well as the two areas where the carb cleaner would come out multiple times. I may be able to take the boat out this afternoon to test. If not today sometime this week. I will report back with results.

 

[AEROCOOK]

If the jet cleaning doesn't fix it, it could be the fuel pump. My 66 and 73 9.5s both had similar issues that were resolved with new pumps. try repeatedly squeezing the primer bulb when it's acting up, it you can get steady RPM at full throttle while doing this, it;s almost certainly a weak pump. Note: I replaced mine with newer 9.9 pumps since nothing was available for the 9.5s.

 

[Calcasieu]

Cleaning the High Speed Orifice Plug did the trick! I took her out and she ran seamlessly at all speeds. I was out on choppy lake austin surrounded by wake surfing boats and was still able to hit 20mph in my 12 foot boat. Thank you all for the help and suggestions!!!

 

[oldboat1]

alone in the 12 footer? Try it from the middle seat, if you haven't done that. (need a tiller extension -- could probably make one.)