Please Help Johnson 150 Check Engine Alarm

Hi , I have 1998 johnson 150Hp (with carbs) and recently Check Engine Alarm came on stayed for 30-40 sec and goes off ,manual direct me to fuel restriction problem, Last time when i used boat engine rpm came down from 3500 to 3000rpm without tuching nothing. Reading all posts so far I changed syphon valve (was rusty anyway), prime bulb ,hose , filter/water separator,check tank for vacuum, engine filter,check compression 100-105psi on all 6 cyl. and now Iam about to change VRO/fuel pump PLEASE HELP

Re: Please Help Johnson 150 Check Engine Alarm

vent on fuel tank, must be clear.

Re: Please Help Johnson 150 Check Engine Alarm

Thanks for reply i did check vent on the tank any time when going boating i fil up tank with fuel until fuel come out from vent I will replace vro pump its on order anyway any other suggetions if its not pump?

Re: Please Help Johnson 150 Check Engine Alarm

Hey vlady I have the sama problem and have done the exact same troubleshooting as you and was wondering if the new pump cured your problem?

Re: Please Help Johnson 150 Check Engine Alarm

yea...did the new pump fix it??????????????

Re: Please Help Johnson 150 Check Engine Alarm

Hi everyone I am back , didn't have time for boating but I have bad news after checking compression (105-110),replacing VRO pump,new primer bulb and all fuel lines,fuel filters (2 total)for water separator filter I used 20 microns filter insted 10 micron,check vent on the fuel tank,check and replaced anti siphon valve, CHECK ENGINE ALARM come back again,even with check engine alarm on, engine sound and worked great no drop RPM pefect normal. I just come back from boat after checking VACUUM SWITCH I did found little amount of FUEL inside, that shuold be vacuum hose. I think next step will be to replace vacuum switch and check diaphragm on VAPOR PUMP that is my last step anybody HAVE ANY OTHER THOUGHTS???

Re: Please Help Johnson 150 Check Engine Alarm

Same issue last year. Did you check for a clogged screen in the fuel pick-up? Did you blow out the pick-up in the tank?

Run the motor off a small tank of premix hooked directly to the fuel pump. That will eliminate everything from the fuel pump on tank.

Re: Please Help Johnson 150 Check Engine Alarm

Thanks for advice Iwas thinking same,even today I replaced anti siphon valve with regular fitting , check engine alarm sometimes come on after 1/2 day boating or more estimated 20-30 gal. of fuel using remote small tank is difficult, how did you solved your problem? Iam wondering how fuel get in vacuum switch?

Re: Please Help Johnson 150 Check Engine Alarm

So My Johnson 150 check engine alarm goes off after a 1/2 day on the lake too. What solved your problem???

Re: Please Help Johnson 150 Check Engine Alarm

Don't forget to clean the main strainer under the airbox.

Re: Please Help Johnson 150 Check Engine Alarm

OMC did have some vacuum switches back in those days that were calibrated wrong. They would go off with 4 " vacuum rather than 7 " as they were supposed to be. You can check them with a vacuum pump and an ohm meter. See you OEM service manual.

Re: Please Help Johnson 150 Check Engine Alarm

Hi, I know about pressure on the vacuum switch (4vs7) and I called johnson tech. support- answer was that is not problem with new VRO pump should not be problem and it wasn't, finally I did found problem in primer bulb also replaced with all other parts -hoses and primer bulb was from West marine double checked it was written 3/8 on everything aparently theare 3/8 diam. on primer bulb wasnt same as Johnson dealer. After all I would reccomend to check fuel lines ,clamps ,check valve in the fuel tank,clamps on hoses and filters , I do have 2filters one on fuel line 15micron (OEM manual call for 20 but trust me that is not problem) and second filter above VRO pump And do yourself favor if you hopping for hoses and primer bulb go to Johnson dealer prices are not bigger than west marine So far all spring and up to date no PROBLEM I am very Happy boat owner.
P.S. I read a lot about VRO pumps if you need to change yours do it DO NOT JUMP PUMP and mix oil and fuel in the tank it is not same engine take oil as it needed (how big is RPM) Importent thing is to check comp. on all cyl. before you go on that step GOOD LUCK reply on message if you have more questions