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

[danoutbard]

Hi,

My name is Dany from Montr?al Canada. My first language is french so if you guys could excuse my english.

I just rebuild a 1985 johnson V4-90hp (my third one) and im having problems tuning it up. After complete overhaul (rebore, pistons,rings, bearings, gaskets, sark plugs, gaz line....) the motor does not get to max rpm (5500) in the water. Wide open, i'm running at only 2200 rpm.

Im runing out of ideas as i am very meticulous and went to all the checks.

Motor starts good, run well with the flush att., compression's at 120 psi (of course it's new) on all four, timing is in specks, vro as been check (still not shure there), reed box ok, carbs rebuild ....

If this had happen to one of you i'd appreciate a little help on this one

Thanks

 

[SparkieBoat]

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

fuel, compression. air , timing, exhaust....pretty much the basics...it would have to be one of those problems..why did you have to rebuild the motor?

 

[danoutbard]

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

fuel, compression. air , timing, exhaust....pretty much the basics...it would have to be one of those problems..why did you have to rebuild the motor?

I bought it to rebuild, it had been sitting outside for one year with two bad pistons ....

 

[boobie]

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

Do a cyl drop test on it to see if it's running on all cyl's. Is the timer base advancing ?

 

[Tim Frank]

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

Carburetors?

 

[BonairII]

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

What happens when you hit 2200 rpm? Does it bog down or anything? Or does it just stop winding up at 2200?

 

[wired247]

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

One of two things

1. Spark advance. Open and close your throttle and make sure the advance mechanism is working and the cable going to the timer base isnt bound up and that the timer is moving freely. No advance, no revs. You just rebuilt the thing and theres half a dozen things that can go wrong with that timing base setup if you didnt make sure it was 100% as it was going together.

2. Float level. Recheck your carbs.

 

[emdsapmgr]

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

Possible the engine is not running on all 4 cyls. Could be a weak ignition component. That engine will seem to run fine on just 2-3 cyls, but won't make power. You can test this yourself. When the engine is running on the garden hose on the trailer, use a special set of insulated pliers and pull one of the spark plug boots off the #1 spark plug. See if the rpm's change once the plug is disconnected. Then reconnect it. Then do plugs 2, 3, 4. When you pull each wire off, the engine rpm's should decrease. If one of the plugs is not firing-when you pull it off, the engine will not change rpm's or sound differently. You can also do a similar test with an inductive timing light. The flashes in the gun will show the quality of spark on each plugwire. If your test shows that all 4 cyls have strong spark, then I'd be looking at the fuel system.

 

[SparkieBoat]

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

my money is on the fuel pump...probably what popped the 2 pistons to begin with

 

[danoutbard]

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

Wow ! Thank you guys for all the response,appreciate it

The carbs have been done by Johnson Dealer, assume its ok there !??

The VRO is my next step, i already canceled the oil section, but i'm gonna replace it all with a pump.

Possible the engine is not running on all 4 cyls Is also a good track to follow , i'll do the test emdsapmgr describe

What happens when you hit 2200 rpm? Does it bog down or anything? Or does it just stop winding up at 2200? Rep:The motor stays a 2200 and seems happy, did fish all day last october and no problems

The spark advance system seems to be doing its job, my timing light says 4 degres at min 24 degres at max

Commander, there is an interresting link on your post :http://issuu.com/cdielectronics/docs...owFlipBtn=true
Says a slow mode could be kicking due to fault in harness like temp switch or so ???

Thanks again from Quebec merci beaucoup

 

[bob johnson]

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

I wonder if you have a bad SLOW warning signal......

anyone know if its possible that a bad sensor could be putting him into SLOW mode?

bob

 

[danoutbard]

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

I wonder if i do have a slow mode...

Does anyone know what year Johnson introduce the slow mode, i’m not shure my 1985 has it..

Thanks again for the help.

Dan

 

[daselbee]

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.....

 

[nwcove]

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

have you tried it in a test tank? it should rev beyond 2200 if its not running on all cyls, but not if it is S.L.O.W mode protected.

 

[toddschubert]

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

I'm thinking timing advance problem. Check all linkage for slack or worn bushing on cam. Mine does similar thing but I still get 4500 when it acts up. I'm waiting on parts to get linkage tightened up for timing arm

 

[Cofe]

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

After reading your post, what comes to my mind is if you are running your motor on the flush connection, do not try to go WOT without having the lower unit submerged under water or your motor could self destruct. A two cycle motor without any load will over rev and could damage or destroy the motor. Just thought to mention that a motor should only go to around 2000 rpm. in neutral, and should go to WOT when placed in forward gear. There is a safety rev limiter when the motor is in neutral.
That being said, if you are running this motor in the water, and it won't go to WOT, I would then suggest that you check to make sure the neutral safety rev limit is releasing when you put the motor in forward gear.

 

[emdsapmgr]

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

That's an older dual power pack engine. No SLOW mode or QUICKSTART. Make sure the link arm is connected between the spark advance lever and the timer base. Have you taken the airbox cover off and visually checked to see if the carb butterflys are opening fully at max throttle? It is possible the sync and link is off. They should be flat (level) @ WOT.

 

[SparkieBoat]

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

those vro pumps are known to go bad regularly...I almost guarantee that was why it needed rebuild to begin with...check that pump..

 

[danoutbard]

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

After reading your post, what comes to my mind is if you are running your motor on the flush connection, do not try to go WOT without having the lower unit submerged under water or your motor could self destruct. A two cycle motor without any load will over rev and could damage or destroy the motor. Just thought to mention that a motor should only go to around 2000 rpm. in neutral, and should go to WOT when placed in forward gear. There is a safety rev limiter when the motor is in neutral.
That being said, if you are running this motor in the water, and it won't go to WOT, I would then suggest that you check to make sure the neutral safety rev limit is releasing when you put the motor in forward gear.

Thank you for the reply.

I don't think this model has a neutral rev limiter.

When i test the motor with the flush, im not realy opening it all the way, i know this could damage the motor

Thanks again for the help

 

[danoutbard]

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

those vro pumps are known to go bad regularly...I almost guarantee that was why it needed rebuild to begin with...check that pump..

Yep thats my next step

Thanks