johnson 175 fast strike engine dies after gas runs out in carb bowls

[hthrus]

cant figure this out doesnt the fuel pump make some kind of sound when key is pushed in johnson 175 fast strike engine dies after gas runs out in carb bowls when in idle but when driving at higher speeds it runs great only thing i do now is my brother put 4 stroke oil in instead of 2 cycle so flushed out best i could but would this burn out the fuel pump .and also checked the compression bottom right was 55-60 all others were in the 90s would appreciate any info on this problem if possiblr

 

[ondarvr]

No, the fuel pump will not make any noise.

The primer solenoid will click when the key is pushed in, sometimes it's hard to hear.

The fuel pump could be weak or have a hole in it, but it could also be an air leak. Squeeze the primer bulb when you think it's going to die, it stays running it could be the fuel pump.

The 4 stroke oil isn't a good thing, but shorrt term use shouldn't be an issue.

The low compression in that one cylinder could be a big issue though. Try a de-carb treatment and see if it get's better, if it doesn't you'l probably need some major repairs.

 

[hthrus]

Thank you for the info i know that the primer solenoid doesn't make any noise could this be the fuel problem? possibly burned out? and de-carb treatment is that just spraying seafoam in carbs?

 

[ondarvr]

The primer system only helps when starting the motor, it has a similar function as a choke, it won't restrict the fuel flow when it's running at an idle. At times they can leak and flood the motor though.

Yes, Seafoam in the carb will work.

 

[Chris1956]

OK, the cylinder with the low compression, likely has damage. Since the boat runs at high speed, the fuel pump is likely good. You likely have a small air leak in the fuel line, which causes the stalling at low speed. Check the main strainer under the airbox and all other fuel line fittings for leaks.

A decarb treatment involves mixing the seafoam into a small amount of fuel and running your motor on it. Spraying seafoam into the carb throats will not clean the carbs. If may clean the cylinders though.

 

[fireman57]

Are you sure that there is no fuel in the carb bowl? If there is not check for a stuck float or junk in a low speed jet in the carbs. If the bottom carb is running out of fuel that could have caused your cylinder damage as it was getting no lubrication because it was getting no fuel. That is where I would start.

 

[hthrus]

stays running now at idle but the 1 cylinder showing only 50 on compression took off the head cleaned all the carbon off the pistons but the bottom left piston was a little loose and looked like it had deteriorated a little on one edge anyway put the head back on now only getting 30 on the compression and the other 2 above it now getting 97 on both so im pretty sure the pistion needs to be replaced do i have to take the block apart or can i get to it behind the carbs?

 

[fireman57]

You might as well tear it all the way down. You will want to replace all the seals and gaskets. Rebuild will take you some time and $ but a good learning experience.

 

[ondarvr]

Just removing the carbon from the top of the piston and head doesn't do the same thing as a decarb treatment, the carbon build up around the rings is what you're trying to remove, but... Since your motor already has a damaged piston and rings a decarb would be useless at this point. This type of damage is frequently caused from carbon build up, but can also be from other things. There is no way to replace the piston without completely tearing the motor appart, and if you're going to take it apart you might as well replace everything and do a total rebuild, the cost won't be much more and I always hate to only replace a few items when I'm that deep into it. Or, just find a different motor.