1980 Johnson 150 bogging down under load

[nlong740]

Hey all,
I have a 1980 Johnson 150 (Model J150TLCSR) on an 18ft bass boat. The motor starts right up and idles fine (with a slight miss every 10 seconds or so).
Here is the story:

I took the boat out and did a test run after I bought it and replaced the transom. I got up on plane fine and went about a quarter mile or so then I pulled over to check some of the electronics and check out the trolling motor etc.. The motor stayed running at idle for the entire time I was pulled over. When I tried to take off again it simply kicked the nose up and bogged down. The motor never actually died but it didnt have any power under load, even though it ran great when i first put it in the water.

Here is what I have done to diagnose the problem:
- Cleaned all 3 carbs completely
- Cleaned fuel filters (2)
- Fuel bulb pumps up and stays hard
- Checked spark, good on all cylinders
- Checked fuel and replaced with new and cleaned fuel tank
- Checked compression --> 100-110 psi on each cylinder
- checked fuel pressure after each pump - At idle After 1st pump the pressure was around 1psi, After 2nd pump the pressure was around 3psi (Any idea what the pressures should be? I was assuming 5-8 psi so I ordered a rebuild kit today and have yet to install it.)
- Checked all fuel lines for rot, cracks and leaks - found nothing bad

After all of this, the problem still persisted. If anyone has some other ideas or things to check that would be great.

 

[Bosunsmate]

Re: 1980 Johnson 150 bogging down under load

Any sign of water on the plugs or pistons being steam cleaned?
Did you check timing?

 

[emdsapmgr]

Re: 1980 Johnson 150 bogging down under load

Recheck for spark. Weak ignition components tend to fail once the engine heats up to normal operating temps. (May run just fine when it's cold/just started.) So, next time out, take an inductive timing light with you. When the engine bogs down again, pull the cowling and check for spark on each plugwire. That engine will seem to run just fine on 4 or 5 cyls in neutral-till you put it in gear. The powerhead temps will be highest at prolonged idle. Once on plane, the pressure relief valves open and the powerhead temps could go down 20 degrees (that's normal.)

 

[nlong740]

Re: 1980 Johnson 150 bogging down under load

Any sign of water on the plugs or pistons being steam cleaned?
Did you check timing?

There is no sign of water on plugs and pistons are not shiny clean from looking into the chamber..

 

[nlong740]

Re: 1980 Johnson 150 bogging down under load

Recheck for spark. Weak ignition components tend to fail once the engine heats up to normal operating temps. (May run just fine when it's cold/just started.) So, next time out, take an inductive timing light with you. When the engine bogs down again, pull the cowling and check for spark on each plugwire. That engine will seem to run just fine on 4 or 5 cyls in neutral-till you put it in gear. The powerhead temps will be highest at prolonged idle. Once on plane, the pressure relief valves open and the powerhead temps could go down 20 degrees (that's normal.)

Thanks, I have a timing light.. I will check that next time as well, do you happen to know what fuel pressure I should be running?

 

[pn]

Re: 1980 Johnson 150 bogging down under load

you shouldn't have to pump the primer bulb to get fuel pressure, pressure should be somewhere between 2-5psi, idle wot. double pumps?

 

[nlong740]

Re: 1980 Johnson 150 bogging down under load

Just an update.. I took the boat out yesterday and it was bogging down again ( still waiting on fuel pump rebuilt kits)... I hit the choke when trying to get on plane and it came to life.. When ever I hold the choke in it runs great, I assume I'm still on the right track with the fuel pumps then.. Thanks for the suggestions everyone, I will keep you posted when I figure out exactly what the problem is.

 

[pn]

Re: 1980 Johnson 150 bogging down under load

well if your wot problem dissappears by letting extra fuel in through your choke, and it's coming to life without pumping the primer bulb, then your fuel pumps are probably fine(check em anyways) most likely you got some crud in carbs, in one of those 4 carbs tucked away in some little orifice

 

[nlong740]

Re: 1980 Johnson 150 bogging down under load

well, I rebuilt the fuel pumps and did a water test today.. Same problem as before, won't get on plane unless i hold the choke in and once on plane i can get a lot more power if i hold the choke in..
Anyone have any other ideas what could be restricting the fuel flow other than weak pumps or carbs (already cleaned them)?

I am considering the possibility of the fuel lines collapsing on the inside once the pumps put enough pressure on the lines at WOT, does this seem plausible? If so, are there common ones that go bad? - I don't like just throwing parts at an issue without knowing what is wrong..

 

[emdsapmgr]

Re: 1980 Johnson 150 bogging down under load

Using the choke adds fuel to the system and the engine runs better. So, just normal running-the engine is running lean. Not good on a 2 stroke. When you had the carbs apart, did you remove all the jets (idle, mids and high speed) and visually inspect them to make sure they are clear/open? Also, check vs the factory parts list to make sure they are the correct jet size and in the correct location in the carb. The fuel lines would not collapse due to excess pressure-not a likely scenario.

 

[nlong740]

Re: 1980 Johnson 150 bogging down under load

Hey again,
I have checked and verified all carburetors and jets are stock and seem fine to me.
I have some concerns I would like some feedback on... I have an oil leak that I have been unable to pin-point its origin. Would anyone happen to know (see picture below) where this oil leak is comming from and is it something I should be worrying about?
- Also I was wondering, if this is a powerhead gasket.. Do you happen to think the powerhead could be loosing enough vacuum in the system due to this leak to cause a weak "impulse" signal to the fuel pumps which would then cause a lean condition in the engine? If so, do you know what the spec's are for the impulse to the fuel pumps?

Johnson 150 Oil Leak Picture

Thanks Again!

 

[emdsapmgr]

Re: 1980 Johnson 150 bogging down under load

When the powerhead base gasket fails on this V4, it will bleed exhaust and exhaust smoke/tar from that joint. Likely that's the problem Aside from it's dirty appearance, the exhaust leak will fill the cowling when running and can/will get reingested back into the airbox- and then the engine. That's the real reason to replace the gasket. You'll have to pull the engine.

 

[Bosunsmate]

Re: 1980 Johnson 150 bogging down under load

Yes as above, you will need to get it done.
The longer you leave it the harder it is to do because as the gasket disintegrates water from the pump and or exhaust causes oxidation/seizing of bolts that hold the powerhead on. Eventually the exhaust will start pressurizing the water inlet into the head which causes big problems.
Be sure to remove the old gasket thoroughly, i use a razor blade to get it all off

 

[emdsapmgr]

Re: 1980 Johnson 150 bogging down under load

When you purchase your replacement V6 flatback powerhead base gasket, you'll want to make sure you get the best one. I believe the factory recommended one is a paper gasket. I wouldn't use it. Bombardier also makes an optional premium base gasket which is much better. It's a pc of aluminum coated with paper on both sides. This will last for a long time. I just purchased one this spring from Bombardier after it was on backorder for 1 1/2 months. Almost seems like that part number is unisted... I'll dig around and find that number for you. It may take a day or two.

 

[nlong740]

Re: 1980 Johnson 150 bogging down under load

Update:
I have not changed the leaking gasket yet, I wanted to prove it was the fuel pumps so I installed a 4-7 psi 30 GPH fuel pump for a test run.. The boat got on plane perfectly and ran great until I got close to top speed the. It started to act like it was starving for fuel again (running around 3800-4000 rpm), I hit the choke while at full throttle and it picked up - close to 5000 rpm.
My thoughts are the original fuel pumps aren't providing the correct flow (possibly because of the leaking gasket causing a vacuum leak?), the electric pump seems to be doing the trick but doesn't have a high enough flow rate..
I'm thinking about simply installing a higher flow electric pump (35-40 GPH) and leaving it alone.. Any thoughts?

Thanks again for all the feedback!

 

[Bosunsmate]

Re: 1980 Johnson 150 bogging down under load

Run it without the cover on, then you can be sure its not exhaust fumes getting in there at high speed

 

[nlong740]

Re: 1980 Johnson 150 bogging down under load

Sorry for such a delay folks, I have been pretty busy lately but thought I would come back to this issue I am still having with my motor.

- Over the past winter I have completely torn the engine down to inspect everything and replace all of the gaskets. All cylinders & pistons look good, no scaring or major wear signs. I have fixed the "oil" leak which was burnt exhaust leaking from the base of the powerhead gasket (gasket was blown out). All gaskets have been replaced and all internal components look good.

I am still having the problem with the engine not getting on plane and low rpm at WOT. I hit the choke and it helps, but doesn't solve the issue. With no choke, it will run about 2800-3000 rpm on plane at WOT. If I hit the choke, it sometimes climbs to 4,000 rpm at WOT. I believe this engine should run over 5,000 rpm but I have never been able to get it there. The holeshot is horrible too, the only way to get on plane is hold the choke in and allow more fuel to the cylinders. The motor starts fine and idles ok, it has a little miss every now and then at idle and coughs out the exhaust.

After reading some other posts, I am starting to think the carbs are about the only thing that could be causing this. Does anyone have a link or good advice on how to properly clean a carb and be absolutely sure it is clean? Should I soak it or is just using spray cleaner good enough? I keep thinking they should be fine because I spray cleaner through all of the jets and it shoots out somewhere else. The carbs look very clean and every hole (that I see) is clear.

Also, I read that Johnson's are supposed to have Champion plugs in them. Mine currently has NGK in it, so I ordered some new plugs (UL-77V). Should get them installed in a day or so.

I also checked the timing today, running about 2-3 degrees advance at idle and 12-13 degrees at about 1800 rpm. Does this sound about right?

I have ran the boat without the cover to make sure it is getting enough fresh air and that didn't help either.

Any advice or things to check is greatly appreciated

Thanks for your help!!!

 

[Bwil]

What ever happened with this. I'm having same issue.

 

[GA_Boater]

What ever happened with this. I'm having same issue.

Have you started a thread. Old and closed.