Help Needed. 1989 Johnson 25 hp converted to a 30/35 HP

[sr522re]

Hi, thanks for reading my post. So I have a 1989 Johnson 25 hp outboard that runs great in stock form. I recently changed out the carb and intake manifold from that of a 30/35 hp motor of a similar year. I've read multiple posts about others doing this with great success so I wanted to try it myself. Now that everything has been changed over, the motor runs, but produces a lean "sneeze" at idle and low rpm speeds. If I cover the carb inlet about half way the sneeze goes away which confirms the lean condition. However, If I adjust the idle/air screw and try to richen the mixture the motor stalls out. I am currently running a #39 orifice at the extreme top of the carburetor and the high speed jet located at the bottom is a #65D. I water tested the boat yesterday and it seems to run fine at full throttle however there is zero performance gain from this new carb and intake. My 16ft side console Tracker would do 23-25 mph in stock form with 25hp and yesterday it topped out at 23 mph. Others that have done this modification have claimed a noticeable increase in speed and performance. What am I missing here? Does anyone have any suggestions for me to try? The only thing I have not changed over yet is the cam which is attached to the magneto armature plate. The parts list shows the cam for a 30 hp motor is the same as the 25 hp so I did not change that out. However the 35 hp motor does show a different cam, but I don't understand how this relates to the lean condition at idle or the lack of top end performance. Can anyone offer me some suggestion? Any advice or input is greatly appreciated.

Motor is a TJ25ELCEB
New carb is a 432705

Thank you!

Chris

 

[crazymanme2]

Maybe Lil' Blue Rude will give his knowledge on this subject.

 

[sr522re]

Maybe Lil' Blue Rude will give his knowledge on this subject.

Hoping so Craig. I've PM'd him. Thanks!

 

[Lockndam25]

I thought I seen a post or a YouTube video and I thought they said the timing was different too, I'm not positive about that, and did you check for a air leak around the carb, sometimes it's the simple things that cause problems

 

[sr522re]

I thought I seen a post or a YouTube video and I thought they said the timing was different too, I'm not positive about that, and did you check for a air leak around the carb, sometimes it's the simple things that cause problems

Yes, I originally suspected the same so I replaced both Reed gasket and intake manifold gasket. Same issue before and after the gasket change. I'll keep searching. Thanks!

 

[Pappy]

When you say the timing cam is to the left do you mean the pick-up marks on the cam?
If so then that needs to be set properly. The carburetor should not be opening before the marks line up with the roller.
Now, if the roller is not touching and the marks are to the left then your timing is too low, hence the sneeze. Advance the timing (twist the throttle grip) after making your roller/throttle blade adjustment then re-adjust your mixture. Yes....re-adjust your mixture, to compensate for the advanced timing. If you have already richened it and the idle RPM is good when the timing is where it is supposed to be then you may be good to go.

 

[sr522re]

To clarify, the timing cam is at the left side of the timing mark . If I center it with my finger the sneeze stops.

I see my thread has been hijacked... It's some what related so lets see where this goes...

 

[Pappy]

Sorry about that but this applies to both of you. The other guy should start his own thread.

 

[sr522re]

Sorry about that but this applies to both of you. The other guy should start his own thread.

No worries pappy, I appreciate the input. My Johnson repair manual is only good up to 30 HP motors and the timing advancement setting is the same for the 25 and the 30 HP motors. However, I wonder if the timing setting is different for the 35 HP? I can't find timing information for the 35. Would a few degrees advanced or retarded really make that big a difference between a lazy motor and a screamer? Thanks for the input!

 

[Pappy]

You have to remember we are talking idle timing here....not WOT timing. Big difference. WOT timing has zero to do with an idle issue.
Idle timing is used as a reference point only. It will get you in the ballpark. The needs of an older, well used engine, may differ in what it needs at idle vs a fresh engine.

 

[hankthecrank]

Whoops. Sorry guys, didn't mean to throw things off track. Hank

 

[stinkfoot]

I have a Clymer manual for OMC motors 2-40hp 1973-1990 if that helps? Pretty sure there is no page for this mod but there is probably idle timing info for a 35. PM me your email if you like. I can send you the relevant page(s).

 

[sr522re]

Just a quick update:

So I adjusted the throttle cable out more and moved the throttle stop idle screw inwards allowing the motor to rev a little higher. Then I was able to richen the carb at idle with the idle mixture screw which brought the revs back down. The sneeze seemed to go away at idle which I think is good. However, now when I rev the engine a little higher the sneeze comes back. Please see the youtube link if you want to see what I am talking about.

https://youtu.be/NuVtRQwVLKI

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!

 

[Lockndam25]

Sounds like a air leaking into fuel somewhere, also there are different size fuel lines maybe the old fuel line is to small to support the amount of fuel the carbs need.

 

[sr522re]

Sounds like a air leaking into fuel somewhere, also there are different size fuel lines maybe the old fuel line is to small to support the amount of fuel the carbs need.

Very possibly. I will go through the fuel lines and replace as needed. Thanks for the thoughts!

 

[Sinkingfast]

If you put a piece of clear tubing near the motor you will see bubbles if there is an air leak. At least from the clear back to the tank. I use a clear fuel filter near the motor and use clear to the fuel pump.

It is near impossible to get things right with bad crank seal or seals. If both seals are bad sometimes one can jet okay but if only one is bad one cyl runs lean and one runs rich. You don't know which cyl is sneezing but i bet its the one with a leaking seal.

jmo...

 

[Pappy]

Why didn't we know you were doing all of this on the hose until the video?
The engine was designed to run at idle with the throttle blade completely closed. Idle timing raises and lowers RPM until the point where, as throttle is advanced, both the timing and carb came into play to produce needed power. This point is located on your throttle cam at the bottom of your mag plate.
Bring your idle back into specs by closing the throttle blade. Adjust timing and fuel mixture to eliminate the lean sneeze again at idle.
Go run your engine, in gear, in the water!!! You cannot duplicate or adjust that engine on the hose to make it do what you want it to! No back pressure or load on the engine in your driveway on the hose!!! Let us know how it runs and we can go from there.
By the way the 35hp cam you noted in your original post is different. The difference is in the profile as the 35hp engine was apparently in need of either more or less carburetor opening at a particular load.

Now, for the folks who are pointing you in the direction of a fuel hose issue. The sole purpose of the fuel hose is to fill the carburetor until the needle and seat closes in the carburetor. Once closed, the fuel tank, hose, primer bulb, fuel pump, etc. all take a break from doing anything until the engine uses a little bit of fuel and they go back to work and put more in the fuel bowl and close that needle against the seat again.
The fuel bowl is a reservoir. Any bubbles supplied by any fuel line will rise to the top of that reservoir of fuel and go out the atmospheric vent in the carburetor.
The idle fuel pick up is located at the BOTTOM of the above fuel reservoir. Not many bubbles there. Once fuel is picked up off the bottom of the fuel bowl it is then mixed, purposely, with a whole bunch of air coming in from an idle air orifice. These bubbles and fuel now make an emulsion in order to help to lift and push the fuel through and to the metered calibration holes located behind that core plug nobody likes to pull out when cleaning their carburetor.
So, once the fuel lines deliver fuel to the carburetor they can not in any way shape or form create a lean sneeze or an over rich condition in the engine.
Any time you want or think your fuel line is creating an issue simply pump the primer bulb and pressurize the fuel line. This will eliminate any air leak into the fuel line. If this issue were at WOT we could look at restrictions of fuel to the carburetor. Why? Because the fuel line/pump may not be able to supply enough fuel to keep that pesky needle closed against the seat in the carb. Beyond the carburetor fuel inlet nipple, the carburetor does all the metering of fuel to the engine.

 

[sr522re]

Why didn't we know you were doing all of this on the hose until the video?
The engine was designed to run at idle with the throttle blade completely closed. Idle timing raises and lowers RPM until the point where, as throttle is advanced, both the timing and carb came into play to produce needed power. This point is located on your throttle cam at the bottom of your mag plate.
Bring your idle back into specs by closing the throttle blade. Adjust timing and fuel mixture to eliminate the lean sneeze again at idle.
Go run your engine, in gear, in the water!!! You cannot duplicate or adjust that engine on the hose to make it do what you want it to! No back pressure or load on the engine in your driveway on the hose!!! Let us know how it runs and we can go from there.
By the way the 35hp cam you noted in your original post is different. The difference is in the profile as the 35hp engine was apparently in need of either more or less carburetor opening at a particular load.

Now, for the folks who are pointing you in the direction of a fuel hose issue. The sole purpose of the fuel hose is to fill the carburetor until the needle and seat closes in the carburetor. Once closed, the fuel tank, hose, primer bulb, fuel pump, etc. all take a break from doing anything until the engine uses a little bit of fuel and they go back to work and put more in the fuel bowl and close that needle against the seat again.
The fuel bowl is a reservoir. Any bubbles supplied by any fuel line will rise to the top of that reservoir of fuel and go out the atmospheric vent in the carburetor.
The idle fuel pick up is located at the BOTTOM of the above fuel reservoir. Not many bubbles there. Once fuel is picked up off the bottom of the fuel bowl it is then mixed, purposely, with a whole bunch of air coming in from an idle air orifice. These bubbles and fuel now make an emulsion in order to help to lift and push the fuel through and to the metered calibration holes located behind that core plug nobody likes to pull out when cleaning their carburetor.
So, once the fuel lines deliver fuel to the carburetor they can not in any way shape or form create a lean sneeze or an over rich condition in the engine.
Any time you want or think your fuel line is creating an issue simply pump the primer bulb and pressurize the fuel line. This will eliminate any air leak into the fuel line. If this issue were at WOT we could look at restrictions of fuel to the carburetor. Why? Because the fuel line/pump may not be able to supply enough fuel to keep that pesky needle closed against the seat in the carb. Beyond the carburetor fuel inlet nipple, the carburetor does all the metering of fuel to the engine.

Very good post Pappy! Thank you very much! I agree with everything you wrote and it is a good reminder of how the fuel flows through the system. The only thing I want to add is that fact that from my fuel pump I have one line that goes to a "T" just before the primer solenoid. From the "T" I have a fuel line that goes directly to the carb bowl as you have mentioned. No air leaks in this area would cause a lean condition as you have mentioned. But the other end of the "T" has a line that goes to the primer solenoid. From the primer there are 2 smaller fuel lines. One that goes directly to the air intake manifold and one that goes to the top of the carb. If my primer solenoid has a seal leak or if either of the two smaller fuel lines have an air leak I could be drawing air into the intake causing a lean condition. But whether or not this could cause the "sneeze" that I am seeing I don't know.

And just to clarify, and I totally agree with you about testing the motor in the water, I just installed this carb and intake on the motor. I wanted to run it on the hose just to confirm it worked. I was hoping to dial it in best I could before water testing. On the water the sneeze was still present and I couldn't make any adjustments know knowing what to look for. I then replaced both intake and carb gaskets thinking it was an air leak. Tested again on the hose just to confirm it would run which does. Still sneezing though as seen in the video. I will absolutely get it back on the water after I look closer at the primer solenoid and fuel lines.

Thanks again for the post. Very informative!

 

[Pappy]

The answer to IF your primer lines are leaking exists in my post. If you think you have a line that is leaking then squeeze the primer bulb. A pressurized line will not allow air into the line. Also a good way to test the integrity of the primer solenoid sealing.
The orifice in the nipple the primer lines go to is so small you can remove that line and go about a 1/4 turn richer on the needle and never know the line is off. Pinch the line with pliers near the nipple for 15 seconds and see if it makes a repeatable definite difference.
Again, you cannot duplicate load on your engine in neutral or in gear on the hose. The carb circuits will not come in properly or at the right time.
Close the throttle blade. Get your idle settled down on the hose, finalize it on the water, then go run the engine.

 

[sr522re]

The answer to IF your primer lines are leaking exists in my post. If you think you have a line that is leaking then squeeze the primer bulb. A pressurized line will not allow air into the line. Also a good way to test the integrity of the primer solenoid sealing.
The orifice in the nipple the primer lines go to is so small you can remove that line and go about a 1/4 turn richer on the needle and never know the line is off. Pinch the line with pliers near the nipple for 15 seconds and see if it makes a repeatable definite difference.
Again, you cannot duplicate load on your engine in neutral or in gear on the hose. The carb circuits will not come in properly or at the right time.
Close the throttle blade. Get your idle settled down on the hose, finalize it on the water, then go run the engine.

Thanks Pappy! Out of curiosity, how do you feel about running in a 55 gallon drum? Better than a hose?

Thanks,