1990 Johnson GT150 problems

[jwtx]

For the pros (persons knowing more than this redneck wrench turn'r) out there I have a couple problems with my GT150. Model# J150STLESB.

1. With the engine cold it idles rough and sneezes. Sometimes will die.

2. Under full excelleration the alarm buzzer goes off but the motor runs fine. Figure this is the fuel restriction alarm

3. This is the puzzling one. When number 2 condition is met the tach goes crazy. It will bounce rapidly back in forth between 2000-5000RPM like someone is turning the power on/off to it. However, engine performance is not affected. Also the tach works fine till the buzzer goes off. The buzzer only comes on above 4500RPM and will silence itself if you bring the RPM's back down below that threshhold.

What I've done:

- Removed all the fuel and fuel tank. Cleaned and reinstalled the tank.
- Installed a remote fuel filter water seperator.
- Replace the inline filter under the engine hood.
- Ran the decarb process. This helped remove about 80% of the sneezing.

I suspect I need to rebuild the carbs for problem 1. But have not idea where to go for problems 2 & 3. The only thing I can think of is a week fuel pump for 2 but what is causing my tach to go crazy? Somehow the two are linked and that has me puzzled.

Thanks.

[stratostn]

I am by all means not a mechanic but my 1990 Johnson GT 175 is cold natured to start as well. I make sure that my primer bulb is full. I will then start it, once it hits I sometimes have to keep bumping my choke to keep it running. Once it starts to idle by itself, I will rev the motor a few times to warm it up with the hotfoot. Now as for your tach it could be your rectifier going bad. Im sure some of the more knowledgeable guys will chime in shortly. keep us posted and keep asking questions untill you get your answer. There are alot of good people on here willing to help.

[ChampioNman]

For the coughing/sneezing test the recirc valves they are under the carbs and attached to the intake manifold. You can soak them in alcohol and try cleaning the screens with a brush use a syringe to see if you can blow air through or not they have a one way membrane in them if you can move liquid through in both directions they must be replaced.
The fuel alarm is before the VRO pump and comes on over 5,000 rpm it will not hinder performance but lets you know not enough fuel is coming into the system. replace your fuel lines from the primer bulb to the motor with BRP 3/8" fuel line. If you are running dual tanks via a tank selector switch, the problem may be with the fuel line from the tanks to the selector switch. I had one give me fits and found that someone had replaced the 3/8" hose from one take to the switch with 5/16" fuel line.

[jwtx]

Thanks. I'll give that a try. It looks as if it may be raining till the weekend but if I can get a test run in I'll let you know.

Championman - What about the tach. Will the alarm cause it to go crazy? It that its way of getting my attention or do I have a bad tach?

[jwtx]

Championman - I checked my fuel hose from the tank to the motor. It is all 3/8 including the new section I installed for the remote filter/water seperator. The boat is a 1991 18' Champion with a single fuel tank. (I figure you would like that.) I just purchased the boat in February so I have been working it over.

One point of interest. Allthough the fuel line is 3/8 from the tank to the motor it is smaller diameter (assume 5/16) from the connector under the hood to the VRO. I found this out when I changed the fuel filter out with a 3/8 filter. It took a little more mussle to push it on. I am affraid of I change out the line under rthe hood to 3/8 I might have leaks. It appears the barbs are designed for smaller line.

[ChampioNman]

Your correct, it is 3/8" into the motor then 5/16" into the fuel system. with a T to the Vacuum switch. The GT's are very succeptable to kinks under the cowl, as most Techs will cut the fuel line at the filter and not compensate for the cut by replacing all the hose from the tank connector back to the VRO. You may also have a leaking hose from the T to the Vacuum switch. Gotta love them rear tank Champs , I ran a GT150 on mine for years and would hit 57-62 not bad on a 201.

On the tach, run the motor on the muffs with a volt meter on the cranking battery leads and look for any volts above 12.6 DC to 13.8 over 15 or under 12.0 means the rectifier is cooked and will cause the tach to be erratic.

[jwtx]

Thanks. I did notice when I replaced that filter it looked a little short. The line does a sharp 180. I'll get some new line and replace it.

I'll have to check the rectifier next time I'm out.

At the present setup the boat will run 58MPH with the GPS. Not bad for a 17 year old motor.
BTW, thinking about putting on a water pressure gauge. Currently I'm not running much trim and think I could run more. (There is not even a hint of a rooster tail.) I have read on other post that too much trim will cause bad water pressure. What are the pressures I should have at WOT and idle?

[jwtx]

I rebuilt the carbs and replaced all the check valves. I had a small fuel leak before I rebuit the carbs. I have found the leak. The bowls are warped.

Someone at OMC must have counted pennies and put on plastic bowls. All three are warped to some degree. Two are warped enough that with fresh gaskets they don't even atempt to seal. I checked and new bowls are $60. I got a used bowl from my local dealer that is only slightly warped. He mentioned I might try double gaskets.

What ya think? I thought too block sanding the bowls down to an even level. I only need a couple 32nds of an inch or so.

Also it appeared that these carbs had never been rebuit. The ink stamp was still on the sides of the carb. It's not there now. Carb cleaner ran over it and took it off.

[Sportwin]

You either have a fuel restriction or a false warning. Hook up a low reading vacuum gauge with some clear line between the fuel tank and engine. It's best to do it as close to the engine as possible. Run the engine. You will see a few air bubbles pass through towards the motor initially but when you accelerate up to speed you should see solid fuel and no bubbles.

The vacuum specification is: No more than 4 in HG.

The vacuum warning switch should not sound the horn until approximately 5 in HG.

If your reading is greater than 4in HG, suspect a bad anti-siphon valve in the fuel tank pickup. The fuel line connects directly to it at the tank. Aluminum anti-siphon valves are not recommended. Only a quality bronze valve should be used. Anything between the fuel tank pickup and the engine could cause a restriction.

In regards to the tach, make sure the two yellow wires coming from the stator are clean and tight. Check all of the wires on that same terminal strip as well.

[ChampioNman]

Do exactly as Sportwin says , you can remove the bowls and flat stand (lap) them with 1500 wet dry and they will seal with a new gasket. But you need the new bowl gaskets (brown), and pull the vacumm on the line into the motor.

[ChampioNman]

Do exactly as Sportwin says , you can remove the bowls and flat stand (lap) them with 1500 wet dry and they will seal with a new gasket. But you need the new bowl gaskets (brown), and pull the vacumm on the line into the motor. Yep make sure you don't have the staror wires crossed on the terminal strip shouldn't matter as it is AC coming in. Just make sure everything is normal.

[jwtx]

I tried the double gasket trick last night and that did work. I'll have to check the vacuum.

Also I did a lake test last night and still have the warning with full throttle. I thought for sure the longer fuel line would work.

I did notice last night when the tach goes crazy the horn comes on and the fuel gage goes nuts as well. Seems like it has got to be electrical. As long as the horn is not sounding all gauges are ok. When the horn goes off both the fuel and tach bounce from one end to the other. The only other gages I have are trim and speed. The speed is not electrical and the trim does not seem to be affected. Maybe on a different circuit?

On a more positive note the sneezing at idle is gone. Seems to idle well. Maybe just a little too low. Idle when warm is 650rpm.

[ChampioNman]

Check all of you grounds on the motor and make sure you have a good tight battery connection, If you have wing nuts get rid of them and get some stainless steel hex nuts and lock washers.

[jwtx]

Will do.

[bigcplumber]

Anybody out there help me with 1991 Johnson GT 150.... bought 1991 Nitro...somebody had completely removed VRO assembly and put and inline electric fuel pump in bilge compartment....which I know is a NoNo....I recently picked up a VRO assembly and bracket...but cannot find spot to mount on engine....would love a picture to see exactly where to mount...I already know how to bypass oiler....will mix gas by myself....or does it really matter where mounted?? As long as pulse line and fuel lines are all routed correctly....any help would be greatly appreciated...picture or two would be awesome.....Thank You.....want to get this boat in the water.

[ChampioNman]

The VRO bracket attaches to the port side of the intake manifold where it attaches to the cylinder head. Just ahead of the starter. The pulse line is under the bottom carbs. The outbound side of the fuel line will go into the fuel tree, make sure to cap off the oil side and secure with a zip tie.

[aimatdeer]

Why is the fuel line from bulb to motor 5/16? I think my 1990 150xp evinrude has3/8 on both sides of the bulb.

[ChampioNman]

The fuel tree and the barb fittings on the carb bowls are 5/16".