58 johnson seahorse 18hp runs best when pressurized tank is higher than motor

[dwittig33]

from my understanding this would generally mean i'm not keeping my prime, but i have checked my hoses and fittings and can't find any leaks. just to clarify when i raise the tank it will run for a good 15-20 seconds, but then will die. with the tank lowered i can get two or three seconds. I have had this thing running great last year, but this year i have had all sorts of troubles. Thanks for your suggestions.

 

[HighTrim]

Does the tank hissss when you remove the cap after running?

First determine if the tank is not doing its job, or if there is an issue on the motor side. Any tanks you can borrow to rule that out? If you keep pumping the button, will it continue to run?

 

[dwittig33]

i believe i just discovered the problem. The gasket on the gas cap is bad, i'm thinking i'm losing air there. I put some silicone on it to repair and will test it when it dries. Do you know where i could order a new gasket for it. It is an old school six gallon can. Thanks for your reply.

 

[HighTrim]

I would rebuild the whole tank.

http://www.vintageoutboard.com/

 

[dwittig33]

so just went out and tested the motor now that I've fixed the leaky gasket on the fuel tank cap. it seems to have good prime now. however the motor will now run longer, but only for about 30 seconds or so before it bogs down, sputters and finally dies. This was happening before my tank issues. I ended up cleaning my carb a month ago to try to solve this and unfortunately it didn't do the trick. any thoughts?

 

[HighTrim]

What about what I reccomended? Try pumping primer button to see if she keeps running. If so , rebuild tank. If not, Look to motor.

Losing spark? What is compression?

 

[dwittig33]

pumped the primer button and it did not help. I have spark and the compression is around 100 in each cylinder. I'm losing a little air around the primer button, however after i fixed the cap gasket i'm getting what should be enough pressure to run the thing. I have a really strong hiss out of the vent in the cap and the primer button is stiff. losing air around the button isn't good, but i don't think it is the problem. Thanks for your help

 

[1946Zephyr]

Have you re-kitted the tank yet? I have a tank here that is constantly loosing pressure while the motor runs, because the housing gasket leaks. While you have your motor running, dump some water around the black housing on top of the tank and see if there are any air bubbles.

 

[dwittig33]

yeah, my tank isn't losing any pressure other than a little around the primer button which i don't believe is enough to cause my problems. i also pumped the primer button while running to test my tank. didnt work so i gotta think my tank is fine. i tore apart my carb and have a couple questions.

1. this is looking from the bottom of the float. its a little nicked up but seems to be operationtional. do you think its too nicked up?
2. the peg that the float is supposed to push up to stop gas flow, is that spring loaded or just loose in there? Thank you.