2001 Johnson 90 stutters at high speed

[Tray]

Hello all,

I have this 90 hp. Been running fine but now has a stutter at higher speeds. It tries to run but keeps stuttering until I throttle back some. Can't tell you the RPM as my gauge doesn't work. I can tell you I have run one full tank of gas (24 gallons) with sea foam. I just filled up recently and have run about 1/3rd tank thru (tank has sea foam in as well).

We recently had it in the shop for flooding where they fixed the stuck choke and supposedly checked everything out.

Some things of note, compression checked fine at 130 per cylinder if I remember right but test was done probably 10-15 runtime hours ago. The bulb will not get hard but does seem to pump gas fine. Starts after a bit of choke and once warm idles fine.

The boat runs fine at lower RPM's.

Suggestions? What to check?

 

[glassmaster68]

Re: 2001 Johnson 90 stutters at high speed

that bulb not pumping up hard could be the culprit,,how old is it?the ethanol in todays gasoline makes the primer bulb hose not last as long as it should.if it dont pump up hard it could have a slight air leak and is having a time trying to pump that much fuel up when your at fuel throttle,of course it could be your carb,maybe a high speed jet getting clogged.hope its as easy as your primer bulb hose tho.

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

that bulb not pumping up hard could be the culprit,,how old is it?the ethanol in todays gasoline makes the primer bulb hose not last as long as it should.if it dont pump up hard it could have a slight air leak and is having a time trying to pump that much fuel up when your at fuel throttle,of course it could be your carb,maybe a high speed jet getting clogged.hope its as easy as your primer bulb hose tho.

The bulb is fairly new. I replaced it when I bought the boat last year as the original bulb would not get hard as well.

The gas I use does not have ethanol in it. I have been very careful when purchasing gas in the past and now we purchase at our local marina and the shop owner has pledged to not use gas with ethanol as long as he can help it.

Any idea how to check for air leak? I was thinking of taking it out and when it starts to stumble, squeeze the bulb to pump more gas. That would tell me if the fuel delivery is the problem correct?

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

I am thinking of replacing the fuel line and bulb. Anyone know what size it may be? I think 3/8". Save me a 45 mile trip to find out!

 

[McGR]

Re: 2001 Johnson 90 stutters at high speed

I've have basically the same motor as yours, a '95 90hp 60 Degree Looper. This motor is new to me this year. I put new fuel lines and bulb on at the beginning of the season. Mine doesn't get hard either (the bulb that is ). Nonetheless, the motor runs great. I've been questioning if this indicates a problem or not too. Perhaps this is a characteristic of these motors?? This is the first or numerous motors I've had that behaved like this. Not to hijack your thread... but I'll be interested to hear what the consensus is regarding this issue.

 

[ezeke]

Re: 2001 Johnson 90 stutters at high speed

I believe that you have a 6400 RPM rev limit on those.

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

I've have basically the same motor as yours, a '95 90hp 60 Degree Looper. This motor is new to me this year. I put new fuel lines and bulb on at the beginning of the season. Mine doesn't get hard either (the bulb that is ). Nonetheless, the motor runs great. I've been questioning if this indicates a problem or not too. Perhaps this is a characteristic of these motors?? This is the first or numerous motors I've had that behaved like this. Not to hijack your thread... but I'll be interested to hear what the consensus is regarding this issue.

Interesting! Would love to hear from others with same motor. Maybe the bulb is not supposed to pump up as solid as other motors?

 

[McGR]

Re: 2001 Johnson 90 stutters at high speed

Interesting! Would love to hear from others with same motor. Maybe the bulb is not supposed to pump up as solid as other motors?

On most motors, a soft bulb is an indication of carb float valves being leaky. I would possibly assume this to be the case with this motor also. However, these motors have a vapor separator in the fuel system. I wonder if the vapor separator has any bearing on the soft bulbs?

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

On most motors, a soft bulb is an indication of carb float valves being leaky. I would possibly assume this to be the case with this motor also. However, these motors have a vapor separator in the fuel system. I wonder if the vapor separator has any bearing on the soft bulbs?

How do I tell if this is the issue?

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

Update.

New bulb installed. Works fine. Still have the problem with cutting out. When I first put it in water after getting it from dealer, idled out past no wake zone, Got up to full throttle no problem. After about 4-8 minutes, it started spitting and cutting out. Slow down past 3500-4000 RPM's and seems to run fine.

I did notice before it started cutting our the max RPM's I could get were 4400 and I should be max around 5500-5800 with max power at 5000. I figured it was to large of a prop or wrong pitch causing this but now I am wondering if it is another clue in my problems.

Dealer thinks its the powerpack now. I have no idea. They have offered to install the part and not charge labor and let me test it out before committing to buying. The issue is dragging the trailer 45 miles to the boat, going thru the hassle of getting it loaded (takes about an hour. Park at launch, bum ride to pier, load up goto dealer, etc....)

How hard is this part to install? Can they do it with boat in water? Do you thinks its the power pack?

 

[bob johnson]

Re: 2001 Johnson 90 stutters at high speed

I am wondering to myself here....what does the bulb have to do with a motor that is running at 3500 rpms?????

I understand you can use the bulb to see if the fuel pump is having problems...but I am wondering is it possible for a bulb to cause high speed problems?


it is just used to transfer the first batch of fuel from the tank to the motor...after that...i was thinking it is just a big spot in the fuel line!!!


now if it collapses, it is a way of telling is there is a blockage...but again it isnt the culprit...just the tell tale

is that right? or not?

I have the same style motor..and there is a FUEL BRACKET/VAPOR SEPARATOR on the motor before the carbs.. and it does have its own float and valve.....certainly could be involved...but once you are running high rpms....the floats better be open!!!!!


bob

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

Bob, Thanks for the info. Question though, if this part was an issue, wouldn't it be a problem at all RPM ranges?

 

[bob johnson]

Re: 2001 Johnson 90 stutters at high speed

Bob, Thanks for the info. Question though, if this part was an issue, wouldn't it be a problem at all RPM ranges?

cant say.....I commented on the bracket-seperator, because McGR had mentioned it...


I figured Id chime in on that part..it does have a float assembly in it...

as for the problem it could be heat induced, then anything elctrical could be suspect....

personally i think the offer of trying it out for free is fantastic...and while they are out there, they could also be verifying what else it could be if it wasnt the power pack....


the issue cant be the prop YET...the prop wouldnt cause this intermitten issue...

wish i could help more


good luck

bob

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

Understood. Mechanic has offered to come to the boat and work on it at the pier. Can't ask for more than that!

On the prop, I meant I should be around 5500 rpm's. Not that the prop was causing the problem.

 

[Craig-]

Re: 2001 Johnson 90 stutters at high speed

8 screws on the covers have to be removed, 4 bolts that hold the coils and pack on, plug wires and pack connector wiring. Takes 20 minutes tops to remove and replace out of the water. A bad coil can show a spark on a grounded plug cranking, but fail a 7/16" spark test. Check your coils first with a spark tester. Try the primer when fault occurs, if RPM gains, fuel starvation issue is likely.

There is no choke to get stuck on this motor. It has a primer that is opened by a solenoid controlled valve when key is pushed in fuel is sprayed into intake. If the valve itself was stuck open, you likely have gummed up main jets creating lean condition at WOT.

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

Update -
Bad power pack. New one installed and ran boat for 20 minutes. No problems!

I don't particularly understand why it would stutter at high speeds and idle and cruise below 4000rpms fine but at least its fixed now.

Thanks to all for advice and suggestions!

 

[cookey]

Re: 2001 Johnson 90 stutters at high speed

Update -
Bad power pack. New one installed and ran boat for 20 minutes. No problems!

I don't particularly understand why it would stutter at high speeds and idle and cruise below 4000rpms fine but at least its fixed now.

Thanks to all for advice and suggestions!

i have similar problem with a mercury 60 when you say power pack what do you mean the battery or coils ??

 

[Craig-]

Re: 2001 Johnson 90 stutters at high speed

i have similar problem with a mercury 60 when you say power pack what do you mean the battery or coils ??

Power pack is J/E term for your ignition control unit, the thing that tells your coils to give the spark plugs some juice.

 

[Craig-]

Re: 2001 Johnson 90 stutters at high speed

Update -
Bad power pack. New one installed and ran boat for 20 minutes. No problems!

I don't particularly understand why it would stutter at high speeds and idle and cruise below 4000rpms fine but at least its fixed now.

Thanks to all for advice and suggestions!

Electronics in them wear out with use, usually heat related. Circuits open up intermittently when demand is high.

 

[Tray]

Re: 2001 Johnson 90 stutters at high speed

i have similar problem with a mercury 60 when you say power pack what do you mean the battery or coils ??

It's the so called "brain" of the motor. Controls the spark, timing, etc... If I was told correctly!