Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Excellent point

Thanks

 

[Joe Reeves]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

A common oversight is to have th eprimary coil wires reversed. Check to make sure that Orange/Blue goes to the top coil and Orange to the bottom.

Also..... the high speed jets are located in the bottom center portion of the carburetor float chambers. Make sure that they are absolutely clean.

I assume that you've made sure that the throttle butterflies are wide open at full throttle?

With the spark plugs removed, the spark on all four cylinders should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

BTW... It appears that your English might be better than mine.

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Thanks Joe, im working hard on my english and you guys give me the oppurtunity to practice it

Thats a good one on the coil being reverse i might have made i booboo there, I know a technique where you can check the polarity of the ignition with a pencil. You place it between and if the spark appears on the left side your ok.

Your scaring me a bit there with the high speed jet in the carbs.This is difficult to confirm right, right?. The carbs have been done by a Johnson Dealer but im not sure he is good with these older model.

Thanks again for the help

Dan

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

That's a bubble back 1985 90HP right? Crossflow?

No SLOW on that one.....

Yes crossflow

What does crossflow means excatly?

Thanks

 

[daselbee]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Well, there are basically two types of two stroke engines: crossflow and looper.
It comes from how the fuel/air mixture is inducted into the cylinder.
This "charge" of fuel air enters through the intake ports, and due to the design of the piston top, it flows a specifc path into the combustion area.

The crossflow pistons have a big "bulge" on their tops which form a "wall" that the fuel charge hits, and deflects it directly upwards toward the top of the cylinder. This inrush of fuel charge simultaneously pushes the exhaust gasses out the exhaust port, purging the cyl making it ready for the compression stroke.

The design of the looper uses a flat top piston, and as fuel charge enters, it swirls or loops around, purging exhaust gasses.

This is very basic...and I am sure there are some on here that will fine tune this explanation.

Plenty of stuff on the internet (Google).

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Here's another interesting track.



When i rebuild the motor i did not replace the four bolts as show'n in picture. These bolts have sealing capacity with o rings. I threw away the rings and replace it with 1000 sealer.

So, what about some pressure lost through these bolts, it would make suction too low to suck gaz through the high speed jet on the card.

I know i m shooting in many direction here, but this something i know i did not do right :facepalm: and might be a or the problem i have

Thank

Dan

 

[wired247]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

So, what about some pressure lost through these bolts, it would make suction too low to suck gaz through the high speed jet on the card.

You know how much air you'd have to suck through those bolt threads to affect the high speed circuit? It would be a massive amount and that is not your problem. Get the weird stuff out of your head and concentrate on the basics. Go to the CDI website and download their troubleshooting guide. Get a factory manual if you don't have one. Check the fuel pump. Check the carbs whether you had a Johnson dealer build them or not. Float levels are crucial on these carbs. Check for spark on all 4 holes. Some of the symptoms you describe are consistent with a bad power pack but check stuff before you buy stuff..

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Thanks for the reply

Im glad i wont have to unmount the block to replace these bolts

Your right im gonna do the basics before going to crazy

Its my third motor i rebuild and its the first one i realy struglge to get going.

The more i discuss with you guys the more i think i m running on only three cylinder. It just that since pistons rings and walls are new, the motor is easy to start. I know that without load the motor can easyly run on three, but when you need power, its another thing,

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Hi again,

I have this pump in the garage to replace the vro, but it has only 2 nipples. I red here that i can cancel the vacuum pulse line and we're ok. Can somebody give me confirmation on that please ?

Thanks

 

[emdsapmgr]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

You are mixing apples and oranges. You need a pulse line vacuum source to activate the bladder in the pump. The pulse line going to your current VRO is a hose. The current pump you show is a typical 88 hp version pump-which mounts directly to the block and uses the pulses from the center gasket hole for the pulses. It's different. Not sure your VRO type block has the pulse port you need. OMC makes a pump which looks like this one, but has a third hose port for the pulse line which should work. Check out this pump: 438559.

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Ok, had time to work on the motor (J90tlcos) this week-end, here's what
i did.

Did a spark test: spark does jump 7/16" on all cylinder

Remove and disassemble the carbs : carbs were clean with no gum no debris (even removed and checked high and low speed jets), ajusted the floats

Removed vro and installed conventional pump : motor started right away

While motor running (with the flush), i pulled the plug cable one at the time to see if this had any effects: pulling cable 1 & 2 and an effects but pulling 3 & 4 (left bank) had barely no effects ? Remender that spark is good on every cylinder and compression is at 120 psi + -

Also, touching the block at cylinder 1 is hot but just warm at cylinder 3

 

[SparkieBoat]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

it is normal for heat to rise and top cylinders to be hotter than bottom ones. if you have compression, sparks, and timing and linkage is all good, then you are pretty much left with a fuel issue. unless you have an intermittent electrical problem, but that does not seem to apply in your case as your problem is consistent. could be fuel line sucking air or bad pump.

 

[bob johnson]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

switch the carbs, and see if the non effect from pulling the plug wire follows the carb.

if so re- rebuild those carbs...and look very carefully at everything....all the little passages and ids in the jets make sure the needles are not bent or clogged

good luck


bob

 

[daselbee]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

Ok, had time to work on the motor (J90tlcos) this week-end, here's what
i did.

Did a spark test: spark does jump 7/16" on all cylinder View attachment 135768

What is that device? I cannot see how you would test spark on the motor with that.

Here is what I use. There is no spark plug anywhere when using the spark gap tester...

While motor running (with the flush), i pulled the plug cable one at the time to see if this had any effects: pulling cable 1 & 2 and an effects but pulling 3 & 4 (left bank) had barely no effects ? Remender that spark is good on every cylinder and compression is at 120 psi + -

Something wrong here. One and three are the starboard bank, and 2 and 4 are the port bank.
goes tlike this:

2______1
4______3

So, you got the coils reversed on the head. I think you have #2 and #4 coils sparking the wrong cylinders. Just swap the spark plug leads to verify. If you do, I am surprised it is not backfiring like crazy.

 

[metriccrescentwrench]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

it is normal for heat to rise and top cylinders to be hotter than bottom ones.

That's a commonly misunderstood old wive's tale. Hot air rises because it is less dense than cooler air. Cooler water sinks because it is more dense than warmer water below it. This isn't so much the flow of heat but rather a denser parcel of air or water displacing less dense material.

"Heat" in a piece of aluminum can't flow from bottom to top as you suggest because aluminum is solid and not a fluid (we've got some bigger problems if it ever does become liquid). Heat flows from where the temperature is higher to where the temperature is lower, period. The only way that heat is removed from the cylinders in a running engine is through a healthy flow of cooling water (or a healthy blast of wind in the case of an air cooled engine).

Also, touching the block at cylinder 1 is hot but just warm at cylinder 3

At idle the cylinders should be quite hot to the touch. You should be able to hold your hand on each for only about 3 or 4 seconds. If one or 2 cylinders are significantly cooler you've located a problem.

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

What is that device? I cannot see how you would test spark on the motor with that.

Here is what I use. There is no spark plug anywhere when using the spark gap tester...

View attachment 135774


Something wrong here. One and three are the starboard bank, and 2 and 4 are the port bank.
goes tlike this:

2______1
4______3

So, you got the coils reversed on the head. I think you have #2 and #4 coils sparking the wrong cylinders. Just swap the spark plug leads to verify. If you do, I am surprised it is not backfiring like crazy.

I understand your point but, the idea is that you wanna see if spark does jump between two points 7/16 appart.
Do you see a problem in using a spark plug to hold the cable?



Yeah you're right... my mistake

2______1
4______3

Thanks

 

[danoutbard]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

switch the carbs, and see if the non effect from pulling the plug wire follows the carb.

if so re- rebuild those carbs...and look very carefully at everything....all the little passages and ids in the jets make sure the needles are not bent or clogged

good luck


bob

I have two Johnson Type II carbs there were no needles ???

Thanks

 

[Joe Reeves]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

I've lost track.... On the previous (pg 1) page, "emdsapmgr" suggests that you have the engine running, then remove a plug wire from a spark plug (one at a time) to observe the resulting rpm drop. This would reveal what cylinder is and is not firing properly. I have seen no mention of that test being performed... perhaps I overlooked it?

If it has not yet been performed, do so and let us know the results.

In your diagram (above post #37) #4 is the slow speed jet(s) 2 to a carb... and #33 is the high speed jet(s) 2 to a carb. There are no adjustable needle valves on that model.

 

[bob johnson]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

View attachment 135795

I have two Johnson Type II carbs there were no needles ???

Thanks

it wasnt ment to be all inclusive.....just as needed where needed

seems if he has spark....but pulling a plug wire off a running motor makes no change in rpm or sound.....then he probbaly isnt getting fuel to that cylinder.... or the firing order is off and he has the wrong wire on the plug....

bob

 

[bob johnson]

Re: Johnson 90 will not go over 2200 rpm at wot in the water after complete overhaul

I've lost track.... On the previous (pg 1) page, "emdsapmgr" suggests that you have the engine running, then remove a plug wire from a spark plug (one at a time) to observe the resulting rpm drop. This would reveal what cylinder is and is not firing properly. I have seen no mention of that test being performed... perhaps I overlooked it?

If it has not yet been performed, do so and let us know the results.

In your diagram (above post #37) #4 is the slow speed jet(s) 2 to a carb... and #33 is the high speed jet(s) 2 to a carb. There are no adjustable needle valves on that model.

on post #31 he goes through what he did pulling one plug wire at a time..... I am assuming one at a time...and NOT two at a time...which could be described as he wrote it...
bob