Early 1990's 150 HP Johnson Fuel Restriction Issue

[Redfish_fisherman]

I have an early 1990's 150 HP Johnson Motor on a 17 ft Sea Pro. When I first bought the boat used, the boat was having a fuel issue that lead from one thing to another. The first issue was that once the motor reached RPM speed's of 5500 it would run for just a few minutes and then die off unless it was kicked back down to 4500-4800 RPM's and then ran fine. At the time the carberators were cleaned and the screen that is at the bottom of the pick up tube that goes into the gas tank was removed from the tube with a wire that I pushed down the pick up tube line to remove it. Also I replaced the fuel wator seperator and also installed all brand new fuel lines leading from the gas tank to the engine as well. After the gas lines were replaced, changed the spark plugs out to the OEM Champion brand spark plugs, and removed the screen that is at the bottom of the pick up line that goes into the gas tank, the engine started running better at 5200 RPMS just not at 5500. For the next couple trips it worked fine until the engine started to have an even worse fuel issues. NOTE: THIS BOAT IS BEING OPERATED AT A 2 STROKE 50:1 RATIO EVEN THOUGH IT DOES HAVE A VRO, BUT THE VRO IS NOT HOOKED UP AS FAR AS THE OIL PORTION.

long story short to this date the all Fuel lines replaced from tank to engine, fuel water seperator replaced, VRO fuel pump rebuilt (OIL PART NOT HOOKED UP 50:1 RATIO), Champion Brand spark plugs replaced, the Red Plug thing that is on the engine for the Choke was leaking so that was replaced. Carberators not cleaned out but the mechanic stated that they were clean when they inspected the drain plug from the bowls, and also the fuel lines dont seem to have any air leaks to allow air to go into the engine.


So what is going on right now after all of the things that have been replaced and fixed, the engine is still messing up and acting like the engine is not getting enough gas at full throttle. The engine will run at an idle speed in gear/out of gear for about 4-5 minutes without having to prime the primer ball. When the engine is at full throttle of half throttle while driving you hav to keep priming the primer ball in order to get it running. Im in the Marine Corps and have my daughter with me for the summer time and she has been wanting to go out on her daddy's new boat fishing all year and she get here and it not working right. Really need some help to resolve the issue or any reccomendations please help out.

 

[emdsapmgr]

If you have to constantly prime the fuel hose bulb in order to keep the engine running at speed, it is starving for fuel. A fuel restriction or some sort, which can include a weak fuel pump. It just won't supply enough fuel to the sustain high speed running. Carbs are consuming more fuel than is being supplied. May be time for a new fuel pump.

 

[Redfish_fisherman]

A new fuel pump cost over 300 dollars and yes it definately has to have the prime bulb primed at high speeds to keep it going wide open. It was just recently rebuilt 2 months ago. Could it possibly been a bad rebuild? I have disconnected the fuel water seperate today and put in a clear see thru fuel filter where the water seperate was to see if the engine if sucking gas at low speeds it is sucking but at high speeds it don't look as it is. At high speeds should it be viewed in the fu filter that I installed like consistantly spraying? I can say this when I prime the bulb at full throttle I can see the gas being pulled from the tank to the engine, but with out hardly anything. Also it does look like there are some bubbles in the filter when it is being pulled from the tank at low speed idle. But the thing is there is no air leakage that I can see from the lines or anything so lost in the sauce

 

[Will Bark]

As I mentioned on the other forum, check your vent in the fuel tank, even if you have to loosen the fuel tank cap. Just a thought. But thank you for your military service.

 

[Redfish_fisherman]

Ok great thank you I will try that when I get home and update accordingly and thank you very much for the appreciation

 

[emdsapmgr]

That engine was not originally designed for an in-line fuel water separator. Good call to bypass the fuel-water separator, at lease till you resolve all the other issues.
Actually, a factory pump could be in the $500 range. Since the fuel system is in question, you may want to expand your sights to look at the anti-siphon valve and the tank fuel pickup-though you probably don't have a fuel restriction since you don't get a high fuel vacuum warning. Check out the fuel hose, too. Occasionally the bulb will fail-actually the ball valves in the hose bulb. The hose bulb should be oriented so that the arrow should be pointing generally upward. If the bulb is laying downhill in the splashwell, the ball valves can be a problem for fuel flow. If every thing checks out, you are back to the fuel pump as a primary culprit.

 

[Redfish_fisherman]

The fuel ball is a brand new ball and I dot think I have a anti siphon valve cause I was able to put a wire down the tube in order to remove the screen at the bottom of the pickup valve.

 

[Redfish_fisherman]

so I got home and rebuilt the fuel pump an tried to run the motor again and it did the same thing started to die off while full throttle. To keep it running I still had to pump the primer bulb to keep it running. I also removed the gas cap and tried to run it but had the same outcome as well. I checked the hose that goes from the fuel pump to the crank case and it is no holes an in great shape. I checked out the crank case pressure valve I guess that what it is called that goes from the fuel pun and to the crank case and It is clean and I am able to blow air thru it and in the hole where that part threads into the crankcase there is no carbon build up either. I checked an tightened down all the other hoses and didn't find no air leaks. So now I'm stumped here any other ideas? Also I was wondering I was told that the pick up tube that goes into my tank is able to be removed. The pick up tube that I have is an elbo type fitting and the tank is plastic. I have pushed a wire down the tube to ensure that the screen at the bottom of the pick up tube is removed. Doing this I can state that I don't have a anti siphon valve either. The elbow has a nut like piece that screws down to the tank and I loosen this piece and try to remove the gotten from the tank with with a pair of pliers it seems that it down want to remove and it looks like it built into the tank is this possible?

 

[Redfish_fisherman]

Also the ball is in the upward position as mentioned as well and all the fuel lines leading from the tank to the engine r brand new ad replaced

 

[Pologreen]

Disclaimer: I am by no means an outboard mechanic, but this past weekend I replaced my VRO with a new unit. Previous to that the previous owner was running premix and using only the fuel pump of the old VRO. Well that died and hence the replacement this weekend. The symptoms were the same as what you describe, if I manually pumped the ball the engine ran fine at high speed, but would die otherwise.

Now to my point. When I was researching the job of replacing my VRO, I remember reading somewhere that it was important to replace the Pulse limiter, I believe one of the symptoms of a bad pulse limiter could be restricted fuel flow. Might be worth doing some web searches and investigating the part and the role it may play for you. Good luck!

 

[jakedaawg]

Borrow a portable tank and 3/8" fuel line and bulb. Run on that. If that does not improve the situation its time to get a gauge and some clear hose and do the tests that your manual states.

 

[Redfish_fisherman]

I checked out the pulse limiter and it has great air flow thru it and also is clean as a whistle. I also replaced the fuel pump with a new pump and it is still doing the same exact same thing so now im lost. Can anyone tell me if i hook up the engine to a smaller tank can it still work the same.

 

[Chris1956]

Does that motor have a vapor separator and vapor pump on it? If so, it could be as simple as the vapor separator cover gasket is leaking, or the vapor pump needs a rebuild.

 

[175se]

Is it a 60 or 90 degree motor that's two different animals. About now I would do a compression test on the port side. If its a x-flow I would pull the by-pass covers to look at the piston & rings on that side. JMHO.

 

[Redfish_fisherman]

this motor is a 1995 150 hp johnson model number J150ELEOM. what is the difference in a 60 or 90 degree motor? compression is great on all cylinders.

 

[Redfish_fisherman]

and yes this engine does a have a vapro pump and seperator as well. CHRIS what does the functionality of the vapor pump? also what would lead you to say the gasket of the vapor seperator is leaking?

 

[Redfish_fisherman]

Chris it does have a vapor separator and vapor pump on it. What is the purpose of the vapor pump? Also can someone tell me would the Vaccum Assembly Switch have anything to do with the fuel pump?

 

[Chris1956]

The vapor separator fills with fuel and that fuel is gravity fed to the OMS pump, mixed with oil and sent to the carbs. The vapor pump sits on top of the vapor separator and assists in filling the separator. If the separator cover leaks vacuum, or the vapor pump is not working correctly, gasoline supply can be affected. Also check the main strainer under the airbox to make sure it's gaskets and O rings are good.

The vacuum assembly switch measure the fuel pressure and sounds an alarm if there is a vacuum in the fuel line. I suppose if it leaks air into the fuel line, it could affect things. Not sure if that is possible or probable.

 

[175se]

You said an early 90s, just trying to verify the motor,the model # answered my question. That being the case my thought was wrong. The 90 deg motor is a different design, it dosent have the covers I mentioned.

 

[Redfish_fisherman]

So it is a 60 degree motor then?