Power Loss 1990 140hp Johnson

[WhiskeyGun]

First off, I am fairly new to boating and boat engines. I bought a used 1996 BlueWave with a 1990 140hp Johnson motor (Model#: j140tlese). It ran great for 2 years up until past few months.

I started getting power loss whereas I try to throttle up and the engine doesn't respond. It has gotten worse with each trip. The RPM's don't build up quick at all. It starts up fine at the first turn of the key. However, when I first noticed the issue, the motor was quieter like a 4 stroke. It idled ok and smooth just quiet. It would even run normal on the first route to my destination. After throttling down for whatever reason and then trying to throttle up, I would barely get a response. Since then it has gotten worse as the motor eventually stalls. Everyone I've talked to said check the fuel system as it seemed to them it was starving for fuel.

So here is what I did so far:

1. Changed all fuel lines, filter, and bulb up to the fuel pump (fuel lines were old and flaking, lots of black specs in filter). However, there was no change in bad behavior.

2. Bypassed main fuel tank, by just putting the fuel hose in a regular gas can. The boat's tone was better, it sounded like a 2 stroke. Most of the power seemed to have returned. Only issue was no hole shot whatsoever, it was slow to build up speed but would eventually get on plane and run WOT/turn like a champ. At that point I suspected problem with fuel tank.

3. To eliminate components of the fuel tank, I got a regular 5 gal boat tank, and installed the anti-siphon valve on it and regular 3/8 hose as pickup. It ran very badly like before after that. Therefore, I suspected the anti-siphon valve.

4. Removed the valve, and the behavior of the engine returned to almost normal, but still no hole shot whatsoever. So my mind turns to weak fuel pump, in which it can't open up the valve and/or losing vacuum.

5. Removed VRO fuel pump (oil side already bypassed by prev owner) and inspected it. Upon removal, I noticed a little bit of gas coming out of the pulse tube which I think is abnormal. Is that abnormal? I took a peek at the inside of the pump, and all diaphragms and o-rings looked ok. In fact, I didn't see any apparent gas in the air motor, which is the only way I think the gas could get into the pulse tube. Maybe it was just sucking it all out. Anyways, I want to know what y'all's thoughts are?

A kit for this thing runs $125 which may be a bust. I've been looking into replacing the pump with a non-vro one. I've see them going for $45-$125. My thoughts are why not just buy the non-vro pump instead of kit at that price. I've talked to a few of the sellers and they all say it should work, but I've yet to find anyone with experience swapping it on my spec motor. The pump descriptions say it should work for up to 140hp 4 cylinder engines.

I am a bit confused as I read some people need two of them in series for the larger motors. I've read that is just for 6 cylinder motors, and others say you should have the series for 125hp+.

Basically, what I want to do is replace the VRO pump (p/n 5007423) with something like this:
https://www.amazon.com/Johnson-Evin...dp/B007I8ZHEG?ie=UTF8&ref_=pe_623860_70668520

Also, am I on the right track? Did anyone have a similar experience?

 

[seabird89]

Funny, I am having similar issues with my '89 OMC 140. I am in the process of replacing the fuel lines. I also suspected the fuel pump, but when I tested it it was good. To test, you can use a vacuum gauge.

I also looked into rebuilding the pump, thinking that it might be weak, and I saw the same non-VRO pumps and considered it but had second thoughts just like you.

I don't know if your tests are valid.

Here is the link for fuel testing including testing the fuel pump.

http://forums.iboats.com/forum/engi.../290505-how-to-testing-your-boats-fuel-system

 

[jakedaawg]

You need to compression test first. Report back results. Then we can go from there.

 

[WhiskeyGun]

Those symptoms in that thread match what's going on for the most part. I'll work on getting actual metrics. I've really just been doing process of elimination.

I actually did a cold compression test, but I don't think I did it properly. I didn't have throttle open and only pulled one plug out at a time. I got exactly 80 on all 4. It'll be awhile before I can get back to it, but I will try hotter with throttle open and all plugs out.

Can I expect higher numbers on a proper warm test?

 

[jakedaawg]

The way you describe your issues leads me to believe that one of the two most likely causes has resulted in bad compression. A compression test is a must first. No point even mentioning the second. A compression test should be done with all plugs out. You can pull the emergency stop switch so you're not shocking yourself if you use the key switch.

 

[ondarvr]

I didn't see where anyone mentioned having cleaned the carbs, since you found black stuff in the filter, after a compression check that would be the first thing on the list.

 

[jakedaawg]

I didn't see where anyone mentioned having cleaned the carbs, since you found black stuff in the filter, after a compression check that would be the first thing on the list.

That was gonna be my second thing but they really need to do the comp check first. No point wasting time in carbs with a bad power head.

 

[WhiskeyGun]

Well, I was able to do a another compression test. Here is what I did, ran it on the muffs for little over 10 minutes until it was hot to the touch. I noticed that one side was warmer than the other by touch (I don't have a way to monitor temps). I pulled all the plugs and open the throttle. My numbers all came up to 90 except one stayed at 80 as before. The cooler side had the cylinder with 80. Also something else new, was that there was some grey goo coming out the exhaust that reeked of gas. For kicks, I pulled the pulse tube off the fuel pump and sure enough there was a bit of clean gas in the pulse line. This ain't lookin' so good :blue:.


Any idea what my next step should be?
Perhaps a ring is sticking, so I might try some seafoam treatment or something. Not really looking to go too deep $$$ into it. I don't mind doing the work, just the bill lol.

 

[ondarvr]

Starving for fuel can destroy a motor quickly, so running it that way is risky, every outing can do more damage.

After saying that, having all the compression numbers low doesn't necessarily mean there's an issue, gauges can be way off, having all fairly close may mean the gauge reads low.

A bit of fuel in the pulse line is minor, and may mean nothing. Fuel dripping out of the exhaust may mean nothing too.

Next step, pull the heads off and look at the condition of the cylinders.

 

[WhiskeyGun]

I know it's been awhile, but things have been busy and I finally got around to working on it. It was the fuel pump that was bad as suspected. The biggest clues were the grey goop and gas in the vacuum line. I discovered in the manual that there is a pump leak test you can perform for the pump. Basically, you unhook the vacuum line, then squeeze the primer bulb. If fuel comes out the vacuum side, your pump has leak. When I did it, all my fuel went through the vacuum. All this time priming my motor, I was just pumping gas into the crankcase. Explains why the bulb never got hard.


Anyways, I bought a single mechanical pump for $45 to test with. It worked, the goop went away. However, it was idling at 1500RPM on muffs now whereas the bad one at 900! I noticed that the throttle arm cam pin didn't line up with the cam roller for the carbs like it says in the manual. I adjusted it down a bit until the RPMs dropped to around 1100 and was closer to the mark. I took it out to the water to further test. It ran good and idled in gear around 650. Never coughed or sneezed. I decided to give it a run around the bay. It came out the hole better than before and never surged at WOT.


I even got a little fishing in ;-).


I still think I have some more tuning up to do, but hopefully I'm on the right track to having it run better than when I bought it.