1989 Johnson 25 hp Converted to 30/35. Help needed!

[racerone]

Time to learn exactly how the primer works !!--------The primer does NOT force fuel into the carburetor bowl !

 

[sr522re]

Time to learn exactly how the primer works !!--------The primer does NOT force fuel into the carburetor bowl !

From the fuel pump I have one fuel line that goes to the primer. Just before the primer there is a T which has one line to the primer and one going directly to the bottom of the carb. From the other end of the primer I have two smaller fuel lines, one that goes to the top of the carb (injecting fuel into the air) and one that goes to the intake manifold (injecting directly into the bottom cylinder through the reeds). When I squeeze the fuel line ball (line from fuel tank to the motor) fuel is distributed through the fuel pump and through all three lines feeding the carb bowl, the top of the carb, and the intake manifold. Keep in mind this is all happening after I have turned the little red knob on the primer which allows me to manually prime the system. Does that make sense to you raceone? Hopefully you now understand how the primer on my motor works.

Next time, rather than just pointing out that you think I should learn "exactly" how it works, you could simply just share your vast knowledge with any of us reading and looking for help. If you still think that I don't understand this correctly I am all ears and still looking for help.

 

[racerone]

Post some pictures of this set-up.--------Something is not right !--------The primer does NOT feed fuel to the bottom of the carburetor bowl !!!----------The primer gets fuel supplied from the pump.----------Then when valve is open feeds fuel into the intake manifold !--------Other wise good luck with your project.

 

[sr522re]

Post some pictures of this set-up.--------Something is not right !--------The primer does NOT feed fuel to the bottom of the carburetor bowl !!!----------The primer gets fuel supplied from the pump.----------Then when valve is open feeds fuel into the intake manifold !--------Other wise good luck with your project.

Correct. Did you see where I said there is a "T" in the line before the primer? The primer feeds the top of the carb and the intake, the pump feeds the bottom of the carb. But when I squeeze the ball and manually bypassed the primer, I feed fuel to all three. With that little knob closed, when I squeeze the primer ball I am only supplying fuel to the bowl. I'll try and get some pics online. Thanks.

 

[racerone]

Edit.

 

[sr522re]

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Post some pictures of this set-up.--------Something is not right !--------The primer does NOT feed fuel to the bottom of the carburetor bowl !!!----------The primer gets fuel supplied from the pump.----------Then when valve is open feeds fuel into the intake manifold !--------Other wise good luck with your project.

 

[Acton]

Quick update:

Two things that now have me a little confused is, when watching the video, the motor runs clean at idle, no smoke, but when I rev it just a little bit and the sneeze begins to occur the motor starts to smoke along with the sneezing. And one last piece to the puzzle which may or may not be related, I am losing my fuel prime if I let the motor sit for more than a few minutes. I have to pump the primer ball a few times before the motor will start again after I let it sit. Perhaps there is an air leak in the fuel line which is allowing me to lose prime as well as allowing for the lean condition?

Thoughts? Any input is always appreciated.

Thank you!

I'm pretty sure Johnny25 had the same problem when he did this conversion. He did a complete walkthrough here on iboats.

I'd read through that tread and see if he had the same problem you're having.

Update: I got the motor on the lake today . . . she died about 50yds off the dock. So off came the engine cover and I started diagnosing. So I found out that she wasn't getting enough fuel and in order to get her to open up and run I had to keep priming the fuel to the intake. So I have some work to do in the garage this weekend.

But that being said, if I kept pumping the primer until I got her full throttle she ran great at WOT. And the boat is a freaking missile now!

Update to my motor not running as well as I wished she had first run. After replacing all my fuel lines I noticed it was drawing fuel and air through the primer line to the intake and spitting fuel threw the line that attaches to the top of the carb while knob is pushed in. See through hoses are awesome Anyway I am assuming that the O rings are bad inside the primer assembly so I will be removing and rebuilding the manual primer today. This should correct the sputtering and cutting out issue I had the other day.

Well if you have a leaky prime like I had just pull the hose going from the prime to the top of the carb while it is running, if there is a lot of fuel spitting out the line while the primer is pushed all the way in then you have a problem. It will spit just a tiny bit or non at all if the primer is good. My bad primer assembly was spitting a lot of fuel into the carb when in the off position which was a big problem getting the motor to run correctly.

He mentions that there are no replacements for the check valves in the fuel primer assembly, he had to replace the whole fuel primer assembly to fix the problem.

I did a lot of research on this conversion process recently myself, but unfortunately it's not possible to convert the 1975 25 HP to the 35 HP model by just changing out the intake manifold and carb. Hope this helps, good luck!

 

[sr522re]

I'm pretty sure Johnny25 had the same problem when he did this conversion. He did a complete walkthrough here on iboats.

I'd read through that tread and see if he had the same problem you're having.







He mentions that there are no replacements for the check valves in the fuel primer assembly, he had to replace the whole fuel primer assembly to fix the problem.

I did a lot of research on this conversion process recently myself, but unfortunately it's not possible to convert the 1975 25 HP to the 35 HP model by just changing out the intake manifold and carb. Hope this helps, good luck!

Awesome post Action! Thank you very much! I will definitely be checking into that further. :thumb:

 

[Tim Frank]

Next time, rather than just pointing out that you think I should learn "exactly" how it works, you could simply just share your vast knowledge with any of us reading and looking for help. If you still think that I don't understand this correctly I am all ears and still looking for help.

That comment probably got rid of Racerone.
I get that this is probably a frustrating business for you, but don't lose sight of the fact that the advice you are getting is offered with good intent, and usually without enough basic info (certainly so in this case) and If you get testy, it does tend to dry up somewhat.
Racerone can be a bit brusque (without being harsh), but his advice is usually the fastest and most direct solution.

That said, the motor history could be relevant. You don't say how long you've had it....buy it new or used. Reason being, if you bought it used, you never know what configuration you have. You can't assume anything is correct. A previous owner may have made a change top OEM and it ran OK so he figured it is OK. Seen that often.
You say it was running great before you started the mod, but now there is a problem. If you still have the parts that you swapped out, it is a quick check to do a reset and see if the original parts also show the "new' symptoms.

Did you ever bother to check the compression and spark per Racerone's post #19. Five minutes to test those and you'd have a baseline.
The fact that you appear to have ignored the suggestion has me wondering why you'd be doing such a significant upgrade without those values.
You may not have as good a grasp of systematic troubleshooting as you think. JMO.

 

[sr522re]

I bought the boat used about 5 years ago. Minimum issues with the motor other than I have to open the hood to manually prime the system before each start. Just pumping the bulb is not enough.

Just checked compression: 120 psi in both cylinders. Spark jumps 1/2" on both leads.
Not ignoring the questions, just busy with kids and life. That and it's back in the 20's outside. A far change from the 60's we had a week ago.

Lastly, I primed the fuel line bulb yesterday till the carb bowl was full. Bulb became rock hard and no fuel passing through the primer solenoid. I checked this morning (24 hrs later) before compression test and fuel line bulb was still solid and bowl was full which is good. Process of elimination... I'm guessing a dirty path in the carburetor or a timing issue. I'm getting close, but need warmer weather to get it back in the water for more testing.

 

[sr522re]

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