Johnson 1985 25hp motor stalls when given throttle. Long, but Detail.

[Malcolm123]

First off, Glad to be here. I am a Newbie to these forums, but not a newbie to forums in general.

Here goes: purchased this motor (model: j25rwlcos) a week ago from a guy I met at the local lake. Motor was all he said it would be. The motor had been sitting for a few months, but when I went to buy the motor, the guy started it right up for me. It took about 5 pulls then it started. Took the motor home and mounted it on my boat, attached my lines and if fired right up everytime I tried it. Reved it up a little and that seemed fine as well. Changed and gapped the plugs (0.30), drained gas tank and bought new gas and mixed at 50:1. Took the boat out to the lake and the motor started up fine. Gave it a little throttle and that was fine. Gave it a little more throttle and it started to bog down. When it bogs if I back up off the throttle it idles fine again. Tried throttle again and it will start to jurking and will cut off if I leave the throttle accelerated. Always starts right back up.

After playing with the throttle by feeding it slowly after time, the motor started to run fine. Fished a little then started the motor back up. Started and idled fine. Let it run a while easily feeding the throttle and after maybe 20 minutes or so I could get some speed out of it. Never went full throttle though.

Came home and found this site and started reading through the old threads. Got some ideas from various posts, maybe not pertaining to my particular motor but made sense. Replaced a couple of hoses. One from the Carb that runs around the motor to the Fuel Pump and one that ran from the primer to the bottom front of the carb. Started the motor and still the same thing. Played with the fuel air mixture. Eventually the motor got right, but it was with the fuel air mixture at it's original location. 1/4 turn out! ( yes I know, I will get to that part) bare with me please. Purchase a Carb rebuild kit. Took the carb to the local boat repair shop and they put the carb in some expensive machine they had back there. The tech told me that te carb looked pretty clean for starter, but he cleaned it anyway. I explained my problem to him and he told me that it's sound too lean especially with the current fuel/air mixture setting. He told me to start with 1 1/2 turns out. Thats where I started once I re-installed the carb and all of it's attachments. Motor still stalled when given gas. I played with the fuel/air mixture while the motor was running for about 30mins. Then the motor finally started to allow me to give throttle. The motor ran just fine after that. I could turn it off and crank it back up and it still ran properly. Took it out to the lake today and it started right up. Gave it some throttle and the same problem occured. Played with it for a while by steadily giving more throttle. Fianally it would take the gas. Took the boat out , fished a little bit and started it back up to go to another location. Same problem again. Help me im stuck!

Note: I am no boat motor mechanic by no means, but im pretty good with small engines. I know how they work and what keeps them going. I haven't bothered the ignition, timing, points etc. at all though. It seems to fire good to me and compression is good so I didnt fool with it.

Thanks in advance. I will answer anything that I may have left out. Oh, pumping the gas tank ball when trying to accelerate doesn't change anything. Im guessing this rules out a bad fuel pump. Also the fuel filter never stays full of gas nor even half full.

Thanks Again

[tashasdaddy]

sounds as if the high speed jets is clogged in the carb. did you remove and clean it? also check spark and compression.

[Malcolm123]

sounds as if the high speed jets is clogged in the carb. did you remove and clean it? also check spark and compression.

Yes. Carb was cleaned in a machine at the local Boat Repair shop. The tech told me that this was a special expensive machine that they use when they repair Carbs. Carb was also rebuilt.

I haven't checked the spark since the motor fires right up.

Compression seems fine, but I guess I could check it.

I will read through the thread history and see if I can find the proper way to check them both.

Thanks

[Cofe]

Could very well be a fuel problem. Here is a diagnostic pic to look at.

[Malcolm123]

Could very well be a fuel problem. Here is a diagnostic pic to look at.

Thanks Cofe! Im about to view the chart.

Update: I just purchased a Compression tester and a Inline Spark Tester.

Tested the compression on both cylinders with and without the other spark plug still attached. Both Cylinders seem good. I got a 110-112 PSI out of both cylinders. This was with and without the other plug still inserted.

Attached the inline Spark Tester and fired the engine up. Engine started right up. The light on the tester was constant. Then I read the diagnostic symptons for the tester's instructions. It stated if engine is running and you give throttle that the light should stay constant. Well it didn't. The light turned off and on as the engine fluttered up and down. The engine would rev up and down and the light on the tester would follow this inconsistency.

Not sure, but maybe I have a ignition problem. Also im not sure if this motor even has points. It has 2 big blocks with wires for each cylinder. These blocks look like voltage regulators or something. They each run from a single block that is mounted on the side of the engine.

The motor has the timing setting for it on the side. Any advise would help and thanks in advance.

Oh, Im also not to sure about this tank. I purchased a new hose with ends and squeeze ball. This tank take came with my first motor, a 1973 Johnson Seahorse 4hp. I do recall that sometimes when I used to take the boat out with the old motor that the engine would sometimes run fine with the choke all the way in. Then sometimes I would have to pull the choke out to different lengths to get a constant highend throttle.

Thanks

[Malcolm123]

Could very well be a fuel problem. Here is a diagnostic pic to look at.

I viewed your chart Cofe. The main category I fit in right now is the Tank and the last column category dealing with a manifold gasket, etc.

I know nothing about the manifold stuff.

I may be underestimating this tank importance. Wish I had another one to test with.

Thanks

[AlTn]

to qualify this answer...I have zilch experience with any 25hp...but somewhere there's a linkage from your carb to the timing cam. There should be a mark on this cam where the roller from the carb linkage should be centered so that the throttle plate is just beginning to open when in the start position and the throttle plate goes to full horizontal when at wot with the timing cam at its highest point. I believe your carb linkage is centered above your carb. This synchronizes your timing advance with yourfuel delivery.

[Malcolm123]

to qualify this answer...I have zilch experience with any 25hp...but somewhere there's a linkage from your carb to the timing cam. There should be a mark on this cam where the roller from the carb linkage should be centered so that the throttle plate is just beginning to open when in the start position and the throttle plate goes to full horizontal when at wot with the timing cam at its highest point. I believe your carb linkage is centered above your carb. This synchronizes your timing advance with yourfuel delivery.

Thanks AlTn.
I have been here reading through the threads and I saw several posts about about the timing advance. Im a pretty decent tinkler and I can usually spot problems if pointed in the right place. Yes, the linkage is above the Carb. A arm plugs into a lever that swings a bunch of stuff. I will study your post very carefully and see if I can find what your referring to. Thanks Again.

Note: not sure if this means anything, but when on water and the motor dies while trying to give gas, sometimes I have to move this wheel/plate a little to allow the neutral pole to go up for neutral.

[Malcolm123]

to qualify this answer...I have zilch experience with any 25hp...but somewhere there's a linkage from your carb to the timing cam. There should be a mark on this cam where the roller from the carb linkage should be centered so that the throttle plate is just beginning to open when in the start position and the throttle plate goes to full horizontal when at wot with the timing cam at its highest point. I believe your carb linkage is centered above your carb. This synchronizes your timing advance with yourfuel delivery.

I just took a look at what you said. I hopes this makes sense and thanks.
There is a linkage that moves the timing cam ( this is the plate that turns on the top of the motor where the flywheel is im guessing) This linkage is connected to the hand throttle. The hand throttle moves the linkage and there is another linkage that runs through this pivoting or swing point that runs towards the front of the motor to a piece that is connected to the carb. This linkage from the carb has a screw type barrel around it for adjustment that is hit and moved when the hand throttle reaches a certain point. All while the timing cam is steadily moving. This screw could be moved to obtain contact earlier or later. Right now the timing cam moves on it's on without hiting this carb linkage screw until the hand throttle is about 3/4 wide open. While this process is in movement, there is a plastic peg that rides the timing cam connected to the carb that opens or closes the carb (there is a notch on the timing cam that lines up with this peg around idle postition. At around 3/4 of hand throttle toward wide open, this peg still remains on the timing cam. If I take the hand throttle to WOT, the peg (which is connected to the carb linkage) pulls completely away from the timing cam.

The screw on the linkage from the carb seems to be what would control how the carb throttle syncs with the timing cam. This screw is controlled by loosening it and sliding it to where you may want contact from the arm that controls the timing cam movement. Whhheeewww!

Thanks. Im trying.

[Malcolm123]

Been reading through the Treads all day. Im thinking I should get the Spark Tester that shows the length of spark instead of the inline one that lights which is the one I purchased today.

Is the inline lighted Spark Tester sufficient?

Thanks

[AlTn]

the "air gap tester" is the way to go...shows strength as well as quality of spark...less'n $10 at most auto part places...I had to get another wider jawed aligator clip to clip the tester to as the tester "jaws" wouldn't open wide enough to clip to a good ground and remain in place while I pulled on the starter rope

[Malcolm123]

the "air gap tester" is the way to go...shows strength as well as quality of spark...less'n $10 at most auto part places...I had to get another wider jawed aligator clip to clip the tester to as the tester "jaws" wouldn't open wide enough to clip to a good ground and remain in place while I pulled on the starter rope

Thanks AlTn, Ill pick one up tomorrow. I will work on the motor some more this weekend. If I cant find the problem, Im going to go ahead and take it to the shop.

Thanks Again

[Malcolm123]

After testing and replacing mostly everything, I am leaning towards the problem being something with the Primer. I replaced the primer hose and while replacing it, all the gas emptied out of the bottom of the carb. Put on the new hose, pumped up the tank line and Wala, engine runs fine.

Tried again the next morning and the same problem was back. Played with the primer for a while and the engine started running fine again. Im ordering a service manual for it.

[jimdd810]

That sounds to me like it might be a fuel pump problem. When it does that if you pump the primer bulb does it run better? When it dies does your bulb stay firm?

[Malcolm123]

That sounds to me like it might be a fuel pump problem. When it does that if you pump the primer bulb does it run better? When it dies does your bulb stay firm?

Priming the Bulb has no affect. Tried that already.

Thanks!

[234rick]

Do both clys. shut off when you open the throttle or just one ?

[Malcolm123]

Do both clys. shut off when you open the throttle or just one ?

Not sure 234rick. Im not even sure how to tell. I will read and see if I can find out how to check it. Im sure its a matter of removing a plug to tell though.

[234rick]

Earlier you said you tested it with a spark tester & it quit firing when you went to wot. Did you check both clys. to see if the same thing was happening ?????????????????????

[Malcolm123]

Earlier you said you tested it with a spark tester & it quit firing when you went to wot. Did you check both clys. to see if the same thing was happening ?????????????????????

Yes, did the test on both Cylinders. I used a inline light type of tester though. I bought a new Gap type tester, but just need to know the gap setting.

Thanks Again

[234rick]

Malcom if you want help you need to answer my questions. Did both clys. quit firing or just one ???????????????????????????????????

[234rick]

I'm trying to find you a quick & cheap answer to your problem.

[AlTn]

7/16" on the air gap....I think confusion is arising as to the fuel line "primer" bulb and the primer bulb on the carb...when you have it running again, try an inductive timing light on each plug wire to check for spark as the motor runs

[234rick]

7/16" on the air gap....I think confusion is arising as to the fuel line "primer" bulb and the primer bulb on the carb...when you have it running again, try an inductive timing light on each plug wire to check for spark as the motor runs

There you go AITn I think you have it. I suspect there has been 10's of thousands of dollars spent on new power packs when it could have been fixed with a simple soldering job. And of course a new power pack also fixes the problem so people never find out it was a wire that broke.

[Malcolm123]

Malcom if you want help you need to answer my questions. Did both clys. quit firing or just one ???????????????????????????????????

Sorry. I am out of town using somene else's computer.
Yes I checked both cylinders with a inline Spark Tester.

The light died on both cyclinders while trying to go WOT.

Thanks again nd sorry.
I have a laptop right now.

[Malcolm123]

BTW

Im referring to the Primer Button that connects to the carb.

Thanks