1985 Johnson 120hp V4 stalling

" While driving across the lak

" While driving across the lake, I can only go about half throttle (maybe 2500 rpm).
If I go faster (3000-4000 rpm) the motor stalls and acts like it is running out of gas.
If I stay slow, all is fine.
When it quits, the bulb in the fuel line is soft, so I pump it up and everything runs great.
There is an in-line filter, and I just replaced the element. (seems okay I think)
Anyone got any ideas what's wrong?

thanks "

the bulb could be bad.or you

the bulb could be bad.or you could have air leaks in the fuel line somewhere. maybe someone else could have more input. id start with the fuel line and bulb though

" Things to check:

Fuel lin

" Things to check:

Fuel lines, for restrictions or air leaks
Anti-siphon valve for blockage
Fuel pump for weak output
Screen on bottom of fuel tank P/U for restriction
Fuel tank vent for blockage

You may want to start by putting a fuel pressure guage in the line between the VRO pump and the carb. This will tell you whether it is actually a fuel supply problem. The problem may be in the carb itself, or may not be fuel at all. It could certainly be a vacuum leak or even a mechanical linkage problem. Good luck "

" Thanks Rick and Mike for you

" Thanks Rick and Mike for your comments.
I will try these things tomorrow.
I have a new fuel line and bulb, and will get it installed tomorrow hopefully.
I'm not sure of the term "anti-siphon valve" ... is that the same as the hand operated bulb for priming the line before running?
The screen in the bottom of the tank P/U, I can check easily when I get back at it.
The tank vent (being solidly closed) I have eliminated at this point. I know this one is a perennial problem for some people.

The fuel pump pressure ... I'll have to read up on how I can check that.

Thanks again. I'll advise how this turns out.
Ron "

"Ron.... Regardless of the pro

"Ron.... Regardless of the problem, it is wise to always check the compression and spark first. Did you?

Compression should be in the range of 100 psi and even on all cylinders. Spark, with the plugs out, should jump a 7/16" gap with a strong blue flame on all cylinders.

If the above checks are okay, I would suspect that you have fouled carburetors which would result in having the engine run lean. The cure would be to remove, clean, and rebuild them.

Also, the timer base under the flyuwheel might be sticking, not hitting the full spark advance stop, which would result in having the engine run at a retarded spark setting.

If that timer base is sticking (or even if it isn't), check the stator assy under the flywheel to see if it may be leaking any substance out of it. That stator is the beginning of the charging and the ignition syatem. If either of the larger (black)coils within the stator start to melt sown, voltage being applied to the powerpack drops which results in erratic ignition.

Spark plugs should be Champion QL77JC4 plugs, with the gap set to .040 .

If a anti siphon valve were at fault, the engine would perform properly at first, then as it is being run a fuel restriction would take place, effectively causing the engine to run lean. From what you've said, the engine does not run properly even at the beginning so this, apparently, is not the case with your engine.

However, I will list the info pertaining to a anti siphon valve so that it may be understood as follows:

(Fuel Anti Siphon Valve)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vaccum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it.

Joe "

" Thanks Joereeves for the gre

" Thanks Joereeves for the great reply.
The compression is 121-125 on all 4 cylinders.
The spark is jumping across a 1/2" gap.

Fouled carburetors, I will have to look into that one.

Timer base under the flywheel, I will have to look into that one and spark plugs too.
Stator assy under the flywheel, I will check that too.

I have 2 red gas tanks. I assume that each may have an anti-siphon valve in the base.
I think this may be an important item to check.

Thanks again,
Ron "

Ron..... Anti siphon valves w

Ron..... Anti siphon valves would exist ONLY with built in tanks. Reread my post about where those anti siphon valves would be located.

Joe (30+ Years With OMC)

" I'm going to try it in t

" I'm going to try it in the lake tomorrow.

From the posts, Things to check:

1. Fuel lines, for restrictions or air leaks.
Changed entire fuel line.

2. Anti-siphon valve on powerhead somewhere for blockage.
Not sure where to find it. Couldn't find any reference in the OMC manual. Maybe I'm blind?

3. Fuel pump for weak output.
Not checked yet.

4. Screen on bottom of fuel tank P/U for restriction.
Checked, cleaned, it was okay.

5. Fuel tank vent for blockage
Checked last time on the lake. No problem.

6. The bulb could be bad.
Replaced it now with a new fuel line.

7. Fouled carburetors?
Not checked yet.

8. Timer base under the flywheel.
Not checked yet.

9. Stator assy under the flywheel.
Measured resistance. Seems okay.

10. The manual made reference to an anti-backfire filter - to check it for any carbon build up. I think that's what it was called anyway. I found it, cleaned it, and put it back on.

11. Oh yes, I checked the vent on the oil reservoir too. It was okay, but I cleaned it up a bit.

That's where I'm at for today.

Thanks for all the great advice guys.
Ron "

" Ron.... You mentioned previo

" Ron.... You mentioned previously (after I replied) that you thought the anti siphon valve was in the bottom of you "two red tanks", and now you state...

"2. Anti-siphon valve on powerhead somewhere for blockage. Not sure where to find it. Couldn't find any reference in the OMC manual. Maybe I'm blind?

I specified exactly where the anti siphon valve is and explained that it would be found only on a built in tank. Is there something wrong with my typing? Is what I'm saying coming across in code?

Using Copy/Paste.... Here's what I said:

"Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. "

" Okay Okay. I'm just a l

" Okay Okay. I'm just a little thick in the head today (hopefully just today).

I have no built in tank, so ... that's it.

Gotta try it out on the lake tomorrow (weather permitting)

thanks "