1999 johnson 90 bogging after 15 seconds @ WOT

Hi All,
this is amazing info board - thank you for all the amazing information..

My 1999 johnson 90 boggs after wot after about 15 seconds (enough for a bowl of fuel).
Seems like MANY folks are having problems with this..

I (and my 20 year experienced Johnson mechanic) have come to the conclusion its a fuel starvation issue.. Ran it on a portable tank - same issue - boggs after wot for 15 seconds.. idles PERFECTLY upto 2000rpm.

Keeping the ball pressurized (manually) FIXES the bogging (runs PERFECT) - so kinda taking out electrical issues. Although not sure the ball needs to be FULLY pressurized to run perfect normally - needs to be FULLY PRESSURIZED manually to run perfect.

Cleaned Carbs (did not replace gaskets or float/needle) - mechanic said "looks like someone was in here trying to fix the problem - all the carbs looked rebuilt" - checked float levels, etc.. all good

Checked the float on the vapor separator - good

Ran the portable tank directly to the engine fuel filter, (cleaned the filter, did not replace)

Did hear on one post that someone put a 5psi pump between the tank and the water separator - mechanic said this was not a good idea as wasn't fixing the problem - just putting a bandaid

Fuel pump holding pressure on both ends - (checked)

Have 5/16 line vs 3/8 line from tank to water separator and then to ball then to engine - calls for 3/8 - mechanics said this is not the problem

Stumping my mechanic is a pretty hard thing to do.. this is crazy..

any suggestions (PLEASE).

Change the fuel pump (although showing good pressure - no leak in pressure) ?
Change the fuel vapor seperator - no leaks ?

holy moly.. please help..

thanks in advance - Cliff

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

Has your mechanic put a timing light on the engine to check to see if you are losing spark on one or more cylinders at W.O.T.? The pumping of the fuel ball may be just a fluke and putting you off the real problem. I had the same issue on a pair of 115s on the back of work boat. I got fooled by squeezing the primer and it wasn't until I did more testing that I found the ignition was ****ting the bed after a short time. So let me get this straight. Pump Ok. Carbs OK. Compression Ok? Leads me to believe you need to check all are firing at W.O.T. I believe 115 and up calls for 3/8 fuel line. Check stator output. Disconnect boat harness and run it on another harness or simply a key switch plugged into engine connector. Make sure all covers are on the engine, presuming this is a 60 degree looper with an optical ignition system.

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

if pumping the bulb fixes the problem you either have a bad fuel pump, fuel line sucking air or a clogged tank vent or pickup. also could be a bad bulb.

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

multimech said:

Has your mechanic put a timing light on the engine to check to see if you are losing spark on one or more cylinders at W.O.T.? The pumping of the fuel ball may be just a fluke and putting you off the real problem. I had the same issue on a pair of 115s on the back of work boat. I got fooled by squeezing the primer and it wasn't until I did more testing that I found the ignition was ****ting the bed after a short time. So let me get this straight. Pump Ok. Carbs OK. Compression Ok? Leads me to believe you need to check all are firing at W.O.T. I believe 115 and up calls for 3/8 fuel line. Check stator output. Disconnect boat harness and run it on another harness or simply a key switch plugged into engine connector. Make sure all covers are on the engine, presuming this is a 60 degree looper with an optical ignition system.

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Hi Multi Mech - Thanks for taking the time to think and respond to my desparate calls for help

You're correct - it's a 60 degree looper with the optical eye (what a concept - holy moly)

Texted my mech this am (6:00) - and will let you know what he says (does). Thinking Mother's day takes precedence over my little 90 johnson..

We did change the powerpack and optical eye (aftermarket) when it had intermittent starting problems (fixed the problem) - did not change the stator as it tested ok (ohm output) per the service manual paramaters. Changed plugs and wires (with matching wires the powerpack manuf. calls for)

DID NOT check the timing -

Is is possible that the pressure side of the fuel pump shows pressure (when tested with the hand pump) but the piston/pressure (inside) is not working at WOT - cant believe how much PLASTIC one can put on an outboard motor

Happy Mother's Day to the women in your life and to all the posters - peace... I'll be back on this board once the mystery is solved for SURE..

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

SparkieBoat said:

if pumping the bulb fixes the problem you either have a bad fuel pump, fuel line sucking air or a clogged tank vent or pickup. also could be a bad bulb.

Click to expand...

Hi Spakie Boat -

Just wrote a thesis on your response and it said - you are not logged in (lost everything

1) fuel shows good pressure and vacuum when tested off the motor (handpump device)

2) checked fuel lines with clearline suction/vacuum tester - tested ok from tank to water separator and then to engine - tested WOT - still ok - changed all lines leading up to the engine - no leaks/sounds when bulb is pressurized - stays pressurized when engine not running..

3) used portable tank to take out boat related problem (fuel tank)

4) changed the bulb - this was a small problem - allowing air into line (evidenced by bubble in clear plastic viewing container on the base of the engine housing.

THANKS FOR THE SUGGESTIONS !!!!
Happy Mothers Day!!!

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

cbmcpa said:

Hi Spakie Boat -

Just wrote a thesis on your response and it said - you are not logged in (lost everything

1) fuel shows good pressure and vacuum when tested off the motor (handpump device)

2) checked fuel lines with clearline suction/vacuum tester - tested ok from tank to water separator and then to engine - tested WOT - still ok - changed all lines leading up to the engine - no leaks/sounds when bulb is pressurized - stays pressurized when engine not running..

3) used portable tank to take out boat related problem (fuel tank)

4) changed the bulb - this was a small problem - allowing air into line (evidenced by bubble in clear plastic viewing container on the base of the engine housing.

THANKS FOR THE SUGGESTIONS !!!!
Happy Mothers Day!!!

Click to expand...

Spoke with a Mechanic suggesting that:

When mixing your own oil (pump disengaged) there is a vacuum nipple that needs to be plugged ? TRUE? or the air/fuel mixture will be out of wack - especially at WOT.. HELP PLEASE

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

yes you must completely plug oil side of vro pump when you premix. got to love the stupid forum that logs you out so quickly..hate that crap, sometimes I cannot even finish a post with out it logging me out..I have learned to copy and paste.

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

SparkieBoat said:

yes you must completely plug oil side of vro pump when you premix. got to love the stupid forum that logs you out so quickly..hate that crap, sometimes I cannot even finish a post with out it logging me out..I have learned to copy and paste.

Click to expand...

thanks.. i'll make sure everything is plugged.. bought the boat 2 months ago and have done nothing but uneventful (not fun) sea trials..

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

it is probably something simple. If you lived near me, I could probably have you running in less than an hour.

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

Since you have a gasoline delivery issue, how is disconnecting the OMS pump going to fix that? You still need to fix the gasoline delivery issue.

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

multimech said:

Has your mechanic put a timing light on the engine to check to see if you are losing spark on one or more cylinders at W.O.T.? The pumping of the fuel ball may be just a fluke and putting you off the real problem. I had the same issue on a pair of 115s on the back of work boat. I got fooled by squeezing the primer and it wasn't until I did more testing that I found the ignition was ****ting the bed after a short time. So let me get this straight. Pump Ok. Carbs OK. Compression Ok? Leads me to believe you need to check all are firing at W.O.T. I believe 115 and up calls for 3/8 fuel line. Check stator output. Disconnect boat harness and run it on another harness or simply a key switch plugged into engine connector. Make sure all covers are on the engine, presuming this is a 60 degree looper with an optical ignition system.

Click to expand...

Multimech.. you were VERY CLOSE..

I was having ignition (key) issues but not enough to change the ignition - the choke mechanism was a little rough - but appeared to work.. the key switch finally died and changed it.

Changed the key switch and FIXED THE PROBLEM.. the key switch appeared to have shorted (the "C" - choke and the "M" - magneto) connections.. I'm thinking the switch was shorting the magneto/powerpack @ WOT.. WOW.. and the bulb was just a "little soft" and that is what threw off my mechanic and myself. the fuel pump tested "GOOD" and as it turns out IS GOOD.. whew.. that was one (2 month) taxing experience..

This is a great board and I thank you Multimech and all the other responders..

Re: 1999 johnson 90 bogging after 15 seconds @ WOT

Hi All,

Thanks again for all the help.. it's always nice to get back to share the "FIX".. it was NOT the key switch..

The Engine was bogging because of two problems:

1) the fuel pump (VRO) was failing @ WOT (very hard to determine - it showed GOOD - good vacuum and good pressure (tested).

and

2) - even harder to determine - the VAPOR SEPARATOR had a HAIRLINE CRACK - it DID NOT LEAK under pressure (idle) - it apparently was sucking air @ WOT ONLY.. after changing the fuel pump (with a new used one I bought for 90.00 - vs 400.00 - and changing out the vapor separator (with a used one) - the engine FINALLY RAN the way it is supposed to 40 kts @ 4500.. it was a 2 month process... and my mechanic has 20 years of experience - never experienced this issue (cracked vapor separator)..

Happy Boating..

Cliff