johnson 90 v4

[hollywoodwayne]

this motor has got me stumped it will run great wot for about 60 seconds then bogs down.I've cleaned carbs,checked compression replaced fuel lines,new filter,new plugs,I think its a fuel issue because when i hit the choke when its starting to stumble it will help.it has the vro disconnected and plugged,gas is 50 to 1.This is a new motor to me so i have no history with it.its around a 89 or 90 year the id tags are gone.I've tried different fuel tanks different lengths of fuel hose.If i pump the fuel ball it helps but doesn't solve the problem.I know that an electric fuel pump is dangerous but I tried one in line in addition to the engines fuel pump(just as a help trying to diagnose the problem),and that also helps but it doesen't fix it.It acts like it has a air leak or a fuel restriction somewhere.It idles great and will run at half throttle if i slightly pump the ball Oh yes it doesen't have any thermostats in it yet.Is there a screen or anything in the vro pump tha could be restricting it or could it be something as simple as an adjustment to the carbs.well this is about all the 1 finger typing i can stand any help would be greatly appreciated

 

[Joe Reeves]

Re: johnson 90 v4

Assuming your compression and spark is normal..... 100+psi & even, strong blue spark jumps a 7/16" gap, I also assume that the electric fuel pump you tried was inline with the original fuel pump (you didn't remove the fuel pump?). If so, possibly the regular fuel pump has a faulty diaphragm which would allow fuel to leak into the crankcase area.

Check to make sure that the carburetors have a proper float setting...... remove the carburetor face plate, pump the fuel primer bulb up hard. If any fuel flows out of the carburetors, correct that problem.

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

 

[hollywoodwayne]

Re: johnson 90 v4

Joe thanks for replying,is there anything in the vro pump that could restrict flow?

 

[Joe Reeves]

Re: johnson 90 v4

I'm not aware of anything there to be restrictive, but a sticking or leaking diaphragm would hinder the pumping action.

 

[emdsapmgr]

Re: johnson 90 v4

A weak fuel pump will provide less fuel than the engine needs. At idle it may run fine. When at full throttle, the engine may consume more fuel than the pump can supply. It may slow down for a period, till the carbs fill back up with fuel, then accellerate again. This may be a repetitive thing. Your constant priming of the fuel bulb hose should overcome a weak fuel pump and and run full throtttle. That will confirm that it is the pump.

 

[hollywoodwayne]

Re: johnson 90 v4

update I built a little boat ramp in my fish pond while my wife was gone so I can work under load and when I spray fuel into the top right carb throat facing the motor it levels out nice does this mean I have a carb issue still or can this be the weak fuel pump?And thanks a lot for the help.Wayne

 

[hollywoodwayne]

Re: johnson 90 v4

I've got a brand new fuel pump to a 1974 evinrude 70 will this work also I discovered the vro elec connection was still hooked up could this have effected it

 

[emdsapmgr]

Re: johnson 90 v4

I would be reluctant to use a 3 cylinder fuel pump to feed a V4 engine. Usually these pumps are different numbers between these two models. The 3 cylinder pump may not feed enough fuel. The VRO pump is mechanical. The electronics feed warning horns. If the engine runs better with fuel sprayed directly into the throats, it is probably running lean. Always possible the jets inside the carb may be restricted with debris or dried fuel. That restriction can absolutely affect engine runability.

 

[Joe Reeves]

Re: johnson 90 v4

when I spray fuel into the top right carb throat facing the motor it levels out nice

That carburetor needs cleaning. First remove the float chamber drain screw to make sure that fuel is actually gaining access to that area. When cleaning, make sure that you manually clean the high speed jets with a piece of single strand steel wire.

 

[hollywoodwayne]

Re: johnson 90 v4

I"ll clean it again,last tim I cleaned everything but the needle and seat so i'll go all the way this time

 

[James R]

Re: johnson 90 v4

Joe will support this that with today's crappy fuel the carbs are more prone to clogging.
You might want to take all the carbs off, strip and clean them properly. I use Gunk Carb and Parts cleaner in a gallon can and soak the carbs per instructions. Always had success. Use new kits and always use Stabil in your fuel. If a carb is not performing on a Two Stroke motor then you are going to burn a cylinder. Not worth taking a chance. The spray cleaners generally are rubbish.
If you don't have a manual it is time to get one. Will save you a lot of money and aggravation.

 

[hollywoodwayne]

Re: johnson 90 v4

thanks guys cleaned carbs again,eliminated the black fuel hookup to the cowl,and i think i had a slight leak where my pulse hose connects to the crankcase,don't know which one of these it was but its runnin great now

 

[Jobless Recovery]

Re: johnson 90 v4

I can't believe that you're describing a problem that we had right after purchasing our used pontoon. We have the exact same motor as you and had the exact same problems. I did everything, rebuilt carbs, replaced all fuel lines, fuel tank, tune ups, ignition nothing mattered until one day there was only one thing left to do and that was when I reached down for the fuel pump bulb and squeezed it. Only to have the motor come back to life every time. It's a obvious fuel delivery problem. We replaced the mechanical fuel pump with another mechanical fuel pump that solved all of the above issues. If you're interested, respond and I will get back to you with fuel pump replacement part numbers.

 

[Janniklindskov]

Re: johnson 90 v4

I can't believe that you're describing a problem that we had right after purchasing our used pontoon. We have the exact same motor as you and had the exact same problems. I did everything, rebuilt carbs, replaced all fuel lines, fuel tank, tune ups, ignition nothing mattered until one day there was only one thing left to do and that was when I reached down for the fuel pump bulb and squeezed it. Only to have the motor come back to life every time. It's a obvious fuel delivery problem. We replaced the mechanical fuel pump with another mechanical fuel pump that solved all of the above issues. If you're interested, respond and I will get back to you with fuel pump replacement part numbers.

Hello
Just read your thread and i'm soon going to replace my VRO with a mechanic pump and need the part number? My engine is a 86 90 hp V4 Johnson
Jannik

 

[SparkieBoat]

Re: johnson 90 v4

OMC VRO fuel pumps sux...I have lost count at how many I have replaced.

 

[Jobless Recovery]

Re: johnson 90 v4

I'll get it to you in a couple days. i wont forget

 

[Jobless Recovery]

Re: johnson 90 v4

Sorry for the delay but here it is: OMC 438559 . My mechanic said that OMC got bought out by Bombardier so you will have to contact Bombadier to get it. Let me know how it works out for you!

 

[hollywoodwayne]

Re: johnson 90 v4

ok thanks to this thread i got the motor running decent.It still didn't seem quite right so I bought a timing light backed it in the water warmed it up took it to wot and the timing was way off,turned it to 28 big difference however now the idle timing is at about 8btdc instead of 4 can this be adjusted without affecting the wot timing?I've read joes wot timing adjustment without the motor running.and I guess I'll need to buy a piston stop tool to do it that way.

 

[emdsapmgr]

Re: johnson 90 v4

The idle timing adjustment will have no affect on the high speed timing. It's adjusted separately. You will want the engine to idle between 650 and 750 rpm, set when the boat is in gear, floating at normal level in the lake. Don't worry about the timing degrees at idle, set it for the correct rpm.

 

[hollywoodwayne]

Re: johnson 90 v4

Well I feel pretty stupid but good at the same time.I've been able to tell the bottom cylinders have been running lean from looking at the plugs.So today I tried something I adjusted the float so that it wasn't parallel but raised up in the back,put her back together took it to the river,and its flying now and the plugs look a lot better,maybe I've got the wrong needle and seat because the way ive got it set now goes against everything i've read but its runnin best ever so I'm leavin it alone now