'85 Merc 60 leaves me stranded twice!

[Joe_the_boatman]

Twice now this engine has run fine from the dock, then quits in the middle of the lake after about 5-10 minutes of running at 80-100% throttle. This is after warming up in the driveway for 20 minutes before launching. After it quits, we got it to "limp" back to the dock by idling in gear. Any throttle I give it will make it shut off. Primer bulb is tight whenever this happens (and during running), and no gas is in the float bowls (nothing came out through the drain screw).

So far:
Cleaned carbs (dunked them), reset floats to correct height, all new gaskets. Tried idle screws from 1/2 turn out to 1 1/2 turns, still cuts off if I give it any throttle. Idle speed changes though.

I'm replacing the fuel diaphragm today. It's old, but doesn't look torn or ripped.

My question is, wouldn't a bad fuel pump give me a squishy primer bulb?
Is it possible I have a (2) sticky needle valve(s)?
What else can I look at?

 

[TommyA]

Re: '85 Merc 60 leaves me stranded twice!

Check to make sure the fuel line connections are tight. It may allow air into the system. Fuel tank vent might be clogged. Take the cap off when the engine dies. Are there any other fittings installed on the fuel line?

 

[Joe_the_boatman]

Re: '85 Merc 60 leaves me stranded twice!

Check to make sure the fuel line connections are tight. It may allow air into the system. Fuel tank vent might be clogged. Take the cap off when the engine dies. Are there any other fittings installed on the fuel line?

I will double check on air leaks and fittings.

I should've mentioned: vents OK (I removed the cap). I moved the fuel pickup to another tank, thinking one was clogged. On the other tank, it sucked the squeeze bulb down, so that pickup's definitely clogged (and it looks like the fuel pump's working right). I bypassed the pickup and put the hose directly into the gas. Still wouldn't run past idle.


Compression's 100/110/110, I'll add, and I also cleaned the fuel filter (screen) before we went out. No fuel leaks from anywhere when I squeeze the bulb hard (so no air leaks?), but again, I'll double check again today.

 

[TommyA]

Re: '85 Merc 60 leaves me stranded twice!

The one time I had a problem like this with my Mariner 75hp I messed with the idle adjustments on the carburetor to fix the problem. I could only get up to half throttle before I made the adjustments. I'm not sure how or why it all of a sudden reached that point but it hasn't re-occurred since then.

 

[Joe_the_boatman]

Re: '85 Merc 60 leaves me stranded twice!

The one time I had a problem like this with my Mariner 75hp I messed with the idle adjustments on the carburetor to fix the problem. I could only get up to half throttle before I made the adjustments. I'm not sure how or why it all of a sudden reached that point but it hasn't re-occurred since then.

Thanks for the input. I've adjusted my idle mixture and idle speed stop, didn't seem to help (I did all this last time it left me stranded).

There has to be an air leak somewhere. I plan on replacing all hoses and the fuel pump diaphragm.

It just bugs me that it runs so well, then conks out on me.

 

[Joe_the_boatman]

Re: '85 Merc 60 leaves me stranded twice!

While going through all fuel lines, I noticed an empty, threaded hole in the carb body. Looks like a previous owner forgot to put in the "bowl vent jet" (.096").

It's just a vent, but I guess it's important enough that Mercury sized that orifice w/ a jet. Going to see if my dealer can order them and will then take on a test run.