25hp Johnson sea horse fuel problems

[lewis7896]

Ok so I am new here but not new to working on boat engines. I have a 1971 Johnson Sea horse with electric start.
I am having fuel trouble and need help. I have replaced the fuel lines from the tank to the fuel pump and installed a new pump. Chem-dipped the carb twice and blew out the jets. Rebuilt the carb except the float and started fresh with good fuel and quality oil. The engine starts without trousble and idles smooth. It idles well in gear and appears to be running fine. When throttle is given it winds up well and usually runs well. However when i let out of the throttle it tends to begin feel like it is loosing fuel and thats when the trouble starts. The engine revs and drops then again. If i manually pump the fuel bulb it picks up and runs fine until the carb bowl empties then I have to do it again. Sometimes it never has any trouble and runs flawless. I put it away for the day and tomorrow it may start and immediatly have trouble. I have checked for fuel restrictions everywhere. And the bowl sometimes will fill with fuel and then the engine stalls. i remove the screw from the carb bowl and no fuel comes out. remove the fuel line from the pump and drain the line, reattach andpump the bulb tight and fuel comes out of the bowl screw. Were off again! until the bowl seems to run out of fuel. I have tried everything. Today it works and twenty minutes from now we stall on the top end. Could this be a float out of adjustment? I have tried to set it level like its supposed to be. HELP!

 

[kfa4303]

Re: 25hp Johnson sea horse fuel problems

Hi lewis. Welcome to iboats. Great old motor you've got there. The tell-tale symptom you gave was that the motor pics up when you manually squeeze the primer bulb, which is the classic sign of a bad/failing fuel pump. I'm not sure if your pump can be rebuilt, or not (I don't think so). If it can't, you'll have to buy a new one or a quality used one.

 

[64osby]

Re: 25hp Johnson sea horse fuel problems

I would double check the fuel pump, the float and the float needle. To me this are the things that could cause your symptoms.

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

Ok just to be clear, I put a brand new OMC fuel pump on the motor during this build. When cranking the engine it will spit fuel three to four feet. So rule out the pump. And why does the thing sometimes seemingly lock the float and not allow fuel into the bowl causing me to bleed the pressure off the lines before again pumping the bulb. I hear what your saying about the pump and squeezing the bulb to keep it running. I said the same thing. Bad pump. But that does not explain the sudden float sticking nor the main fact that this issue is intermittent. Bad pump is a bad pump?? Correct? Sometimes you cannot force fuel to the carb with the primer bulb. Indicating the needle is closed. Do you think a simple needle and seat are causing all this along with the float?? It never gives the same symptoms except one loss of power on the top end. Due to or a consequence of??????

 

[Georgesalmon]

Re: 25hp Johnson sea horse fuel problems

Said you rebuilt the carb. With a kit including a new needle and seat? Sure sounds like your needle is sticking closed and won't let fuel in. Did you adjust the floats right? If the float is not adjusted right it might hold the needle closed. I had a bad float once but that caused to much gas not to little.

EDIT: If the float is not loose on the pin maybe it is staying in the raised position? If you take the carb off and tip it over can you hear the float moving up and down?

 

[lindy46]

Re: 25hp Johnson sea horse fuel problems

Does the needle have a "rubber" tip? Did you install the little spring clip to help keep it from sticking?

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

Does the needle have a "rubber" tip? Did you install the little spring clip to help keep it from sticking?

Ok, I did install a new needle and seat in the carb during the build. The spring was also relpaced. However I cannot say if the tip was rubber. I recall it being black and it was not soft. I have looked at a hundred times but never gave the tip any attention to detail. I agree with the float sticking. And I agree that the needle could be the problem. What about the stalling on the top end, can the sticky needle create a starved for fuel effect on the top end because it is not opening all the way, Therefore the bowl is not filling. Sounds like it. Common sense goes a long way and I ordered a new needle and seat today. As for the carb float I ordered a new one as well. I did adjust the float to be level by bending the metal tab as directed for adjustment. It moves freely when I have had it apart and I did try the tipping it upside down to hear it a coulpe times and it was working right at the moment. If this doesn't fix the issue I hope we are not dealing with an ignition of fuel on the top end at WOT. I dont think that will be the case. I agree with what you guys are saying and it makes sense to me! Thank you for the help. Sometimes its good to get other opinions, even if only to confirm your own suspicions!

 

[kfa4303]

Re: 25hp Johnson sea horse fuel problems

Hi Lewis. If the needle had/has a black tip, it was rubber. Some needles are/were solid metal. If it is failing at WOT then, I suspect that the high speed passage in the carb is clogged/dirty. However, if that doesn't fix it, then you may have an issue with the ignition. Not to worry, the much loved OMC "universal magneto" is very cheap and easy to work on yourself, but lets focus on one issue at a time. After the fuel system is straightened out, you can worry about the spark. Good luck. Keep us posted.

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

Hi Lewis. If the needle had/has a black tip, it was rubber. Some needles are/were solid metal. If it is failing at WOT then, I suspect that the high speed passage in the carb is clogged/dirty. However, if that doesn't fix it, then you may have an issue with the ignition. Not to worry, the much loved OMC "universal magneto" is very cheap and easy to work on yourself, but lets focus on one issue at a time. After the fuel system is straightened out, you can worry about the spark. Good luck. Keep us posted.

Ok, I took the time to take the carb off again and dip it one more time in chem dip for 30 minutes. I used an air hose and blew out the high speed passage. Then upon reassembly of the carb I fully inspected the needle. It is silver in color and has a very hard black tip. So hard it infact appears to be a coating over the metal. Most needles i have been around with
rubber tips had some amount of "soft". This one is hard as a rock. I will wait to put the bowl back on until the new needle and seat arrive in a couple days. Does this needle sound right? I will keep you posted. Thanks

 

[kfa4303]

Re: 25hp Johnson sea horse fuel problems

hmmm...you're right that the rubber tipped needles have a bit of flex in them, while the metal needles are usually shiny all over. perhaps it just corrosion on the needle. either way, I would just wait for the new parts to arrive. thankfully, it will all go back together pretty easily and it should run much more smoothly.

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

On a hunch I dove Into the carb again and took the seat out of the carb. I found a small particle of rubber beneath the seat. So after removal I inspected the needle. It does have a rubber tip and to my surprise is more flexible than I thought. I reassembled the carb after blowing the whole thing out again. Put it on the water and it immediately fired and off we went. Within seconds I noticed a new problem now. It would wind up to half throttle Inspite of how much I gave it it would only rev about half way. It still had a slight surge in the rpms and I think I may have some more of that mystery rubber piece in the high speed jet. Any clues as to if this could be my problem? But it's new from where this post started!

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

How should the float be set?

 

[kfa4303]

Re: 25hp Johnson sea horse fuel problems

hi lewis.Glad you found that little bit of rubber. The float should be level and parallel to the cab body when held upside down. Scroll about 3/4 of the way down in the link below for pics under the heading "Assemble the New Top Half of the Carburetor". Was the motor having troubles while in gear, or at idle? Surging is usually due to an air leak some where in the fuel system.

http://www.outboard-boat-motor-repa...hnson 5.5 HP 1954-1964 Carburetor Tune-UP.htm

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

The engine surges under load. Really bad on the top end. I have put a clear hose on the pump and connected it to the bowl. Watched carefully for air leaks. None were noticed. When this started I could pump the bulb and keep it going strong. Now that doesn't help. I agree to the air leak. I have had this thing apart at least 25 times and I just ordered another new carb kit. Hoping to eliminate air at the carb with new gaskets. It's perplexing me!

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

I have the float properly set and again re checked for air leaks. This has to be in the carb. I had a friend tell me a leak down test would tell me if the engine was able to produce enough vaccum at WOT to keep fuel pumping. Some kind of lower crank seal could be bad?????never heard of that but do not know what it is.

 

[AlTn]

Re: 25hp Johnson sea horse fuel problems

do you have another fuel tank and line to test with?...the crankshaft has a seal on the top and bottom which seal it in the crankcase

 

[lewis7896]

Re: 25hp Johnson sea horse fuel problems

do you have another fuel tank and line to test with?...the crankshaft has a seal on the top and bottom which seal it in the crankcase

Ok so the needle and seat arrived today. I installed them as well as new gaskets. Out to the water i went. after the initial warm up for a couple minutes at idle i took off and she ran like never before! No hesitation on the top end and at WOT. After a solid hour of up and down the RPM range, without any trouble, I was satisfied. Engine starts really easy and idles very well. It has plenty of power and sounds smooth. Combination of finding the mystery piece of rubber under the seat and a new needle which I am sure was sticking when the rubber piece covered the intake hole I belive was the culprit. The fact that it would not allow me to pump the bowl full manually was the clue that makes sense now. The rubber piece was restricting the flow of fuel into the bowl. Thank you all so much! The old Seahorse lives again!! I couldnt be more proud. I completely rebuilt the engine and lower unit. A first for me. I have always tinkered with the old engines, but never completely rebuilt one. Mark that off the Bucket List! THANKS AGAIN

 

[kfa4303]

Re: 25hp Johnson sea horse fuel problems

SWEEET!!!! Happy boating. Vroom-vroom!