91 Johnson 15 hp wont start

Just tried to get this motor going for spring fishing and I now have a sore arm from pulling on it. Ran it dry before putting it up last year and it is stored inside. Primer bulb pumps up nice and firm, new plugs with good fire gapped to 030. I have checked all the fuel line connections and they are good, I have gas to the carburetor. Was able to get it running once for about 15 secs by spraying a little gas in the cylnders and then it quit. I assume that it is not getting gas properly. Just did a serach on this forum and found the article by "dolluper" on these motors . I have removed the carb and I am on my way to get a carb kit. The only thing I have noticed is that the black plastic part on top of the carb that holds the idle screw is cracked slightly where the air silencer screws on, could this be the problem ? Any thoughts or suggestions would be appreciated <br />Thanks<br /> cer79

Re: 91 Johnson 15 hp wont start

Replace it CER.....ask for PN 433973. It's an upgrade for the cover. Got more beef in it so it's not so likely to crack when the screws are tightened. 'Bout $25 American.<br /><br />Make sure you blow out all passages in the carb wiht carb cleaner and follow up with compressed air. When you put the new idle tube in, it's a little tube for the idle circuit, put a little engine oil in it. This will help it slip over the connection Tubes. Connect it first to the carb body. And do make sure the idle connections are open. They have really small holes and can plug real easy.

Re: 91 Johnson 15 hp wont start

OBJ Thank you for your reply. I tried a little sealant on the outside of the crack . It is not cracked through,installed the carb kit adjusted the slow speed idle out from bottom 1 1/4turn and tried starting the motor. On several trys it will almost start but wont stay running, tried adjusting the slow speed screw but no difference. I will try ordering a new top plate for it but I dont think this is the problem as this I think was cracked when the air silencer was removed to replace the recoil starter last year and it ran fine last year. I will take it a part again put the carb cleaner to it and blow it out in good shape . As far as the slow speed screw goes any recommendations on setting it ? Also in the kit I got I did not have a seat of any kind for it or I did not realize what it was. Is there some sort of seat for it? Once again thanks for your help

Re: 91 Johnson 15 hp wont start

Just to update while waiting for part to come in . Pulled the carb off again and cleaned with carb cleaner checked all openings and put back on motor. Choked, Pulled over and the motor will fire and run for about 5 to 10 secs , while this was happening was able to reach in and open up the throttle and was able to keep the engine running through a combination of the throttle and choke . If I put the choke in the "no choke" position and just hold down the throttle the motor will eventually die unless I choke it a little more. For sure it is starving for gas. Pulled the line off going from the fuel pump to the carb and pulled the motor over and the gas will come out . is this a valid test for the fuel pump? Any thoughts or comments are appreciated. <br />Thx <br /> cer79

Re: 91 Johnson 15 hp wont start

Did you to completly dissasimble the carbs.

Re: 91 Johnson 15 hp wont start

CER...just for grins, pull the inlet fuel line off the carb. Make sure the pump is empty. Now blow on the carb outlet nipple. Can you blow back through the pump? If you can, replace/rebuild the pump. You should not be able to blow back through the pump from the outlet.

Re: 91 Johnson 15 hp wont start

Hoss yes took everything apart. <br /><br />OBJ I wil give that a try tommorow and post what I find. I have been pouring over the post I have found using the search function here hoping to find some more info . Thank you for your help it is greatly appreciated <br />Thx<br /> cer79

Re: 91 Johnson 15 hp wont start

Like OBJ said, that idle tube needs replacing. They're known to be cracked every now and then and now and then, etc..Also, make sure that brass tube that it's connected to is clear. Use a very small torchhead cleaner to clear that passage.((((((((very important))))))))<br /> As far as the top cover goes, they're known to crack because of the thin casting and the hard red needle valve keeper. Flaw in manufacturing. G luck

Re: 91 Johnson 15 hp wont start

cvx <br />Replaced that tube with a new one that came in the carb kit . Also took a very fine wire and did just as you suggested . Still waitng on the top plate. I am going to test the fuel pump as suggested by OBJ tonight when I get home from work and pull the carb off again (I am getting pretty effcient at it now) and clean it out one more time. On thing I neglected to mention is that while the motor was running I tried pumping the primer bulb and it made no difference. Could the symptoms I am describing be caused by a cracked top plate cause as I said earlier it does not appear to be cracked through and I beleive this was done last year when the recoil starter was worked on and it ran fine all last year after that . Thanks to all for for your suggestions and help! <br />Thx <br /> cer79

Re: 91 Johnson 15 hp wont start

Cer...make sure the fuel line from the pump to the carb is clear. Needle rough setting....from gently seated, try 2 1/2 turns out. Don't think the crack on the top would cause the problem your having....just possibly an idle problem.

Re: 91 Johnson 15 hp wont start

OBJ<br />If I knew where you lived I would buy you a tall cold frosty one. You hit it with the 2 1/2 turns setting . Choked it, pulled it and away it went running great now in the garbage can. Thanks to you I will soon be out in search of fiddleheads and trout! Once again thanks to you and all those who responded to my post<br /><br />cer79

Re: 91 Johnson 15 hp wont start

Now THAT'S what I like to hear..... <br /><br />When you get out on the water, after the engine has warmed up, just kick it in gear and adjust the knob for best idle in gear with the throttle all the way back....careful not to lean it out to much. <br /><br />Good fishing CER!