1996 Johnson 150 HP

Hello, this is my first post here and I am looking for some help. I have twin 1996 150 hp Johnson engines. I'm having trouble with it going 10 mph on GPS on wide open throttle. The engine rubs up fine by pushing the buttons on the shifter with no problem it goes up to 6500 RPM. Does anyone have any suggestions on what could be causing me problems? Any input is much appreciated.

First, do not rev up to 6500RPM in neutral. An engine with no load can rev very high and could lead to major problems.

I have several questions first. Sorry there are no immediate answers, but we need a better idea of what's happening here before much advice can be given.

Are both engines running smooth or is there any roughness? If one runs great but the other isn't right that would explain a lot.

What RPM are you seeing on both engines at WOT (Wide Open Throttle) with them in forward gear? Are the engines getting up to max RPM (5,000-5,500) or are they some value below that?

What size boat are these mounted on and how long have you owned the boat? If it's new to you, did it ever run right? If you've owned it a while, what was the performance before this problem started?

Do you have a System Check gauge or a tech equipped with System Check lights? Are there any warning lights or audible alarms? A Check Engine light and/or constant warning horn could mean a fuel restriction. If both engines are behaving the exact same then it's quite possible you have a fuel problem. Water in the fuel, clogged fuel filter, collapsed/kinked fuel hose, stuck anti-siphon valve. Those are all things to check if your issue is related to fuel delivery.

Do you have a System Check light for Water Temp? If so, then you're overheating and the 10MPH limit means the SLOW feature has been activated.

What, if any, maintenance has been done to the engines recently?

Please answer these questions and we can go from there.

Thank you for the advice, I didn't know I wasn't supposed to rev it up that high in neutral.


Are both engines running smooth or is there any roughness?
Both engines are idling the same with no roughness

What RPM are you seeing on both engines at WOT (Wide Open Throttle) with them in forward gear?
anywhere from 1200-1400

Are the engines getting up to max RPM (5,000-5,500) or are they some value below that?
same value below that

What size boat are these mounted on and how long have you owned the boat?
It's a 26' wellcraft and I've had it a little bit over 2 years


If it's new to you, did it ever run right? If you've owned it a while, what was the performance before this problem started?
It did run right. It use to do about 30 on GPS at about 5000 RPM.

Do you have a System Check gauge or a tech equipped with System Check lights? Are there any warning lights or audible alarms?
The oil alarm keeps going off.

What, if any, maintenance has been done to the engines recently?
Fuel water separator for both engines, changed the spark plugs and before that, I had no problem

Okay, good info. So everything was fine until the filter and spark plug change?

what spark plugs did you install? The OIS 2000 ignition system is very picky and you should only use Champion QL78YC plugs in these engines. There are a lot of engines where NGK will cross reference, but your engine is NOT one of them.

did you prefill fill the water separating fuel filters? Maybe you have an air lock in the filter housing that’s preventing good flow.

The SLOW feature limits you to 2500 RPM so that doesn’t sound like your issue.

Are you you getting a low oil or no oil light? Have you filled the oil reservoirs? I don’t recall, but that might also be an alarm for the oil side of your VRO pump. Possible, but it’s seems odd that both would fail at the same time.

So everything was fine until the filter and spark plug change?
Yes, everything was fine

what spark plugs did you install? The OIS 2000 ignition system is very picky and you should only use Champion QL78YC plugs in these engines. There are a lot of engines where NGK will cross reference, but your engine is NOT one of them.
yes, these are the exact ones I used. I used the same number for the fuel water separator and I checked for clogged lines and all lines were fine. I did find a small leak and I replaced that gasket.

did you prefill fill the water separating fuel filters? Maybe you have an air lock in the filter housing that’s preventing good flow.
I did prefill with fuel. I will check the flow on Thursday.

• Are you you getting a low oil or no oil light? Have you filled the oil reservoirs? I don’t recall, but that might also be an alarm for the oil side of your VRO pump. Possible, but it’s seems odd that both would fail at the same time.
  Oil level is fuel on reservors and the low oil light is the one coming on with alarm​

How are your fuel primer bulbs? Do they prime up firm or do they suck flat?

I’m not sure what to think about the low oil warning. Do you have system check on each engine? Is the oil light on both or just one? Did you prime the oil lines to each engine? Maybe you’re not getting oil up to the VRO?

I just finished refilling the water fuel separators with fuel, pumped it till the primer bulb got hard and checked for any other leaks on VRO and carburetors and there are no leaks

mrmoe said:

How are your fuel primer bulbs?
They prime up firm.

Is the oil light on both or just one?
Just the right side

Did you prime the oil lines to each engine?
yes. when I changed the spark plugs I noticed that it was burning very rich on the oil on both engines

Click to expand...

Okay, now we're getting somewhere. My troubleshooting knowledge of the VRO is limited, but that sounds like the source of your problem. Do you have oily plugs on both engines or just the starboard engine? Air leaks in the fuel lines leading to the VRO pump, or cracked components in the VRO itself can lead to lean fuel, over-oiling, and the gummy spark plugs you mentioned.

Do the fuel primer bulbs stay full or do the suck flat?

I hate to reference other sites, but this article is a good read about the VRO system: http://continuouswave.com/whaler/reference/VRO.html

Here are some quotes from the article:
"[FONT=&quot]One of the most common causes of engine failure is water in the remote oil tank. Condensation and spray can build up over time and, like water in a fuel tank, it stays on the bottom to be sucked up at the worst possible moment. Water pumps through the system as easily as oil......draw off some fluid from the base of the tank and squirt it into a clean jar. Look for sediment or water .....any signs of contamination, the tank should be flushed clean, the filter (OMC P/N 174377) changed, and the oil line purged. "

"[/FONT][FONT=&quot]air leaks can also trigger "NO OIL" alarms, commonly at startup, idle, and trolling speeds."

"[/FONT][FONT=&quot]Air leaks and/or fuel restrictions will affect the VRO and usually show up as excessive oil consumption, smoking, and fouling plugs."
[/FONT]

I just got back from the lake and check for any air in the systems. Took off the fuel water separators off and filled them with new clean fuel (the fuel that was in there was clean) checked the fuel hose for cracks or kinks and everything was okay. I did go in reverse today, I got a lot more RPMS than I do in forward under load.

mrmoe said:

I just got back from the lake and check for any air in the systems. Took off the fuel water separators off and filled them with new clean fuel (the fuel that was in there was clean) checked the fuel hose for cracks or kinks and everything was okay. I did go in reverse today, I got a lot more RPMS than I do in forward under load.

Click to expand...

Okay, this is strange you can get RPM in reverse but not forward. I'm wondering if you have some odd throttle linkage/cable issue going on? It doesn't explain the oil light, but the RPM issue is odd. Maybe I'm grasping at straws but it's worth checking off the list.

Try this:
Remove motor hoods and take off the silencers.
With the engines off use the lever to move into forward gear at full throttle position.
Now, look in the throat of each carburetor and see if all the butterflies are completely open.
If so, then the linkage is working fine.
If ALL butterflies are NOT fully open then you have some problem with the cable or linkage.

Beyond this, you may need to do a complete vacuum test/check on the VRO's to make sure there aren't any issues with one or both. Here are links to a couple of methods.
https://www.outboardmarine.co.nz/catalogues/VRO-pump-tests.pdf
https://www.boatpartstore.com/vro.asp

mrmoe said:

I didn't know I wasn't supposed to rev it up that high in neutral.

Click to expand...

Nothing to do with your engine problem here... just a bit of information for you, and perhaps others, to avoid a bigger one.

Revving a outboard engine in neutral can, and has for quite a few boaters resulted in a runaway engine whereas the engine actually turns into a diesel with the rpms continually increasing with no end until finally connecting rods start flying out the side of the crankcase. Pulling the plug wires off, closing the throttle, turning the key off... none of these actions will have any effect.

Should this happen to you or anyone reading this, the only way to stop the engine, to my knowledge, is to clog the carburetor air intake with rags or whatever you have on hand.

That great looking neighbor gal that's been watching you... yeah, her shirt'll do it! :rolleyes: