2000 johnson 35

Recently bought a 2000 johnson 35hp for my personal boat and i now know why they sold it!
It will start! Thats about the only good thing. Thought it was the carbs so ordered kits for them and they look like they were just purchased from omc they are so clean. I adjusted the floats, since they were out of adjustment, and went ahead and cleaned them just to be sure something else wasnt in them i couldnt see. Got them back on, along with all new fuel lines under the hood, and same thing. Starts up, will run for a second, then die. (Note i did do a link and sync after installing carbs)

Well after that i gave it throttle and shes a screamer!!! So i went back into carbs thinking i missed something which happens and absolutely zero! still look new! Well now its time for fire! Check all coils and they ohm fine. the bottom pack is new so i checked actual fire. im getting 7/16" easy out of the bottom and its HOT!! The top and middle are barely making it and the spark is rather weak! So im assuming coils could be the culprit.

The only thing i havent done yet is checked compression, which i ran out of time, and pulled the fuel pumps apart. I am heavily leaning towards ordering pump repairs due to the gaskets leaking and screws being somewhat loose. I believe whoever worked on it before may have pulled them apart not knowing what they were doing and just half way put them back on.

So as long as you get it started and give it throttle she runs great! but you have to rev off and on because holding steady rpm isnt going to happen..

also reeds appear to be fine as well. and nothing leads me to believe its been ran hot.

You didn't run this before buying it ??

I honestly suspect many people do not. I don't usually, but I won't pay much for an old motor either. I'll roll the dice for a hundro but not a thou.

Pappy said:

Welcome. There is only one pack on this engine. Should have three primaries that go to the coils. Check and clean each primary connection at the coil. I have found several with arc marks that affect idle primarily.
Always check compression before going too far into the enigne. You have a 3-cylinder apparently. Has the oil tank been disconnected yet? Not mentioned.
As far as fuel pumps go, if they will supply fuel at higher RPM they will certainly supply at idle. If you doubt this then squeeze the primer bulb at the RPM the issue exists at and this will by-pass the pumps and fill carb bowls independent of the pumps. The main reason for the second pump on this engine was to supply enough pressure and volume to run the oil pump which is/was located at the bottom of the oil tank.
Lets do something simple here and richen the idle mixtures 1/4 of a turn and see how the idle responds.

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Glad your still here pappy! Yes the oil injection is obsolete. I have also tried 1/4 turn method. Its like anywhere you leave it in the rpms say 1k, or 1500, or 2k itll run there for a sec then die. if you constantly work the throttle it wont do it. Also im running it in a barrel. Going to check compression shortly and see what that comes up with

airshot said:

You didn't run this before buying it ??

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Heck no! for $100 i woulda been a fool not to buy it.

LaqueRatt said:

I honestly suspect many people do not. I don't usually, but I won't pay much for an old motor either. I'll roll the dice for a hundro but not a thou.

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Im in it cheap or i wouldnt have gotten it. usually ones i buy cheap turn into parts. this one actually looked decent. got it home and it fired up so going through it

Are you sure you don't have the idle mixture set a bit too rich? Does it smoke much?

Bign0703 said:

Heck no! for $100 i woulda been a fool not to buy it.

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That makes more sense!!

thill said:

Are you sure you don't have the idle mixture set a bit too rich? Does it smoke much?

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tried idle from 1.5 out to 6 where they were when i got it and no change

Pappy said:

Lets do this. Start by seeing it is fuel or ignition. Got some plastic ignition pliers? Pull the spark plug end of an ignition wire and hold it next to the spark plug while running. Close enough to where the plug will will arc and make contact. See if you lose spark when the issue happens. Do this enough times to where you are sure one way or another. If you have a sparky that will work as well or a timing light would be the safest.

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pappy that was my first thing i tried. used spark tester and top 2 coild wont hit 7/16 gap but very close. but its a weak spark. No3 cylinder will run 7/16 and looks like a 220v welder throwing a 7018 welding rod down a pass. still havent gotten time to compression test yet.
also plugs are rather wet on top two cylinders bottom is burning great which leads me to believe its coils

Pappy said:

You can swap a coil from cylinder to cylinder if you want. See where it leads you. Do it long enough to where there is no doubt about the answer.

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ok pappy! Lets see what you recommend here!?
i have now replaced fuel lines, fuel pumps (just because i had them), rebuilt carb, plugs, cleaned ground really good on coil packs and got them good, and fired right up! Then dies. So i finally broke out the compression tester and 70 psi across all three at wide open throttle. Note this is cold due to it not staying running.

Head gasket, reeds, rings? What would you think?

You didn't answer Pappys question about swapping coils back in May.

Also, a quick way to troubleshoot a head gasket is try the compression test with the adjacent plugs in, and then again out. If the number changes you know compression is leaking over. The number might go up or down, but your looking for a change.

I'd get a second gauge to verify the 70psi low compression before tearing into it for rings

Pappy said:

Different compression gauges read totally different from each other.
Secondly, you do not need to open the throttle to check compression. Any good gauge that has a check valve in the line will give you an accurate compression reading with the throttle closed.
Your fuel pumps on this engine are different than the 2-cylinder engines. Did you check and purchase the correct parts? Won't be the fuel pumps anyway but you should know they are different.
Gypsy - this engine has no head gasket! Also - thanks for the support in getting him to try what I have already asked that he do.

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Pappy I’m sorry I’ve been mia on this thread. I did finally get around on it and swapped coils around along with known working coils from a motor I purchased. Needed up doing a compression test with a couple other gauges and got the same and even lower. Ended up tearing it down and honing the cylinders since they looked good and put new rings in it and she runs amazing now! Also when it comes to fuel pumps and electronics it’s always oem when available and they were the correct ones. I can’t stand to cheap out on stuff like that. I run mine on the Mississippi River and can’t be left stranded for an Amazon knockoff part.

Bign0703 said:

Heck no! for $100 i woulda been a fool not to buy it.

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Makes more sense now....

airshot said:

Makes more sense now....

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Yea I’m still not in it but a little over 500 now and runs amazing! Does well on the Mississippi River for me.

Bign0703 said:

Pappy I’m sorry I’ve been mia on this thread. I did finally get around on it and swapped coils around along with known working coils from a motor I purchased. Needed up doing a compression test with a couple other gauges and got the same and even lower. Ended up tearing it down and honing the cylinders since they looked good and put new rings in it and she runs amazing now! Also when it comes to fuel pumps and electronics it’s always oem when available and they were the correct ones. I can’t stand to cheap out on stuff like that. I run mine on the Mississippi River and can’t be left stranded for an Amazon knockoff part.

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Nice job! Congrats!