update=90 150 johnson gt runs great but wont go over 2800rpm

[chris71167]

90 nitro tracker with a 90 johnson 150 gt. just bought a week ago changed fuel added seafoam rebuilt all 3 carbs they were nasty and leaking new champion plugs compression is 90psi on all cylinders new fuel filter changed water pump lower unit oil. timed and adjusted linkage according to the manual(was very careful checked and rechecked) runs perfect in the driveway can run up past 3k for a min perfectly. got it idling on the lake perfectly. can increase throttle stops about 1500rpm if i increase throttle past that it stumbles boggs etc and will die. so something is dropping out or not working correctly under load? please help im a ASE certified master tech(automobiles) im either missing something or im just baffled at this sec. this is my first boat.

 

[Silvertip]

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

Just like a car, it needs fuel and spark and it all needs to happen at the right time. Something is missing. Just like a car, an engine reving in neutral may sound perfectly normal but put a load on it and it becomes a slug so that test means nothing. You obviously own or have access to an inductive timing light. Use it to check for spark under load. If you were inside the carbs, the high speed jets need to be squeaky clean so if only the float bowl and needle & seat were removed and cleaned there is reason to do it all over again. Throttle opening fully? Timing advancing properly?

 

[chris71167]

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

yes i timed the motor. today i let seafoam soak in the cylinder walls. checked spark output on all the coils #2 and #6 coils are inop should have checked them earlier... swapped the orange primary circuit wires to make sure it wasnt the ECM or computer figured like in cars companion cylinders sometimes share the same driver in the ECM for ignition but nope just 2 dead coils. SO i will replace those might do all of them if cheap enough. any other suggestions if the coils(which should fix it as it was running on 4 instead of 6) Anything else i should check?

 

[whalerfreak22]

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

if you have 2 dead coils that will make it bog also really clean out those high speed jets.good luck!

 

[chris71167]

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

well the jets should be clean as i rebuilt them carb cleanerand compressed air does the job. Thanks for the help guys im gonna slap those coils on, and maybe check the timing again and let yea know how it goes.

 

[chris71167]

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

Re: 90 150 johnson gt boggs and stalls wont go over 1500rpm

ok well i put the new coils on and started sea foam had soaked for a couple hours, smoked like crazy and burned all the gunk out. It sounded and ran 100% better really snappy throttle and sounded really good. adjusted the linkage and put the boat on the water, had to turned the idle screw up one turn at a time and got my idle in gear in the water set. it runs awsome but i cant get it to go over 2800 rpm or around threre. also noticed i cant get it to plane out. The only thing i noticed is when i messed with the idle screw it kinda threw off my throttle cam. What could cause it to not run over 2800rpm ? It runs great no bogging or missing or anything just wont go lol.

 

[cdoliver]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

do a search on SLOW mode.

 

[chris71167]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

sounds like it is stuck in SLOW mode. since it never goes above that speed. I have already changed the water pump. and the outing before tonights i checked the head temps with a laser thermometer 105F a little low? i guess ill check the sensors and if the ok its the power pack? i havnt heard any alarms go off.

 

[emdsapmgr]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

A blocking diode in the engine harness can send a signal to the power pack to limit rpm's to 2500 on engines which have the 35 amp alternator system-which includes the XP/GT line of 150 engines. It will tell the power pack to put the engine into SLOW if it thinks either head temp switch has reached 203 degrees. You can disconnect one head switch and test run the engine, then repeat your test run by disconnecting the same switch on the other head. If it runs over 2500 with either head switch disconnected, one/both of those head switches is faulty. There is also a test for the power pack. If you connect an ohmmeter between power pack terminals E and F, and you get a meter reading of 96 +- 10 ohms, replace the pack.

 

[chris71167]

testing results for SLOW mode issue

testing results for SLOW mode issue

test results= according to my manual i tested the slow mode.
checked each temp sensor to ground left side 20ohms right side Open

checked the diode the big red plug on left side of engine to harness side of temp sensor. one direction open other direction 9ohms

on the six pin connector to the stator pins E and F to each other had 101ohms. Ground to pin E 27ohms Pin F to ground 27ohms.

Checked pins E and F to CD6T-shaped looper big black box with all the orange wires Pin F to ground 9ohms Pin E 25ohms.

both temp sensors when grounded turn buzzer on, buzzer doesnt come on when the problem happens in the water and motor doesnt overheat.

just slightly confused im testing it as the book said, so if my testing and results are correct i need the diode... and a temp sensor on the left side and the power pack? deal with the wires coming off of it right under the flywheel on the back side? seems odd. Thanks for all your help chris

 

[chris71167]

SLOW mode test results...

SLOW mode test results...

the whole 96+- 10 ohms reading sounds funny to me. Most parts that have a resistance spec like 200-250 ohms say replace if OUT of spec not like my book says if it is in this spec replace. never seen that before if it calls for 80-120 ohm reading and i get open reading or no resistance its ok? doesnt make sense anyways if someone could look at my results from the post above and give me an input ill go get the parts i need tommorow

 

[emdsapmgr]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

Sounds like you need a new port head temp switch: 583441. I prefer to condemn power packs based upon their voltage outputs as measured through a peak-reading voltmeter. You should get 175 volts from the pack coil lead to ground on that meter- see page 3-40, 3-41 of the service manual.

 

[chris71167]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

so put new port temp sensor in, and put a brand new oem power pack. rechecked all the linkage and timing. all good. now it idles fine....but boggs when trying to accelerat past 1000rpm just immediatly sputters and dies. also having a hard time starting every once in a while. im going to pull my hair out with this thing. i thought about putting the old power pack back on since atleast it ran great then just nothing over 2500 im totally lost and back to square one.. any ideas at all.

 

[jonesg]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

Choke it (or spray fuel into throats) when it starts to splutter, if it picks up rpm the carbs are clogged or some other restriction.

Also try pumping the bulb, if the valve is stuck or the bulb pointing in the wrong direction the fuel might be backflowing to the tank and starving the carbs.

 

[emdsapmgr]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

You could also put an inductive timing light on each plugwire when you try to accelerate past 1000 rpm. It will show if you are getting spark on all 6 wires.

 

[chris71167]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

I've tried pumping the bulb while running it still dies or kills it. Bulb feels ok. Checked all the fire on the plugs. New plugs 4 new coils new power pack. Feels like its not getting fuel, no fouling on plugs. I think ill check fuel quality/ water contaminatuon check fuel pressure etc start at square one. Btw I can't find a factory service manual for my model tried all the site on here and couldn't find it oh well

 

[emdsapmgr]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

You can get an original factory service manual from the original publisher, Ken Cook Co., in Milwaukee. Possible you have a weak fuel pump. Have you check the fuel output from the fuel pump?

 

[chris71167]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

Nope have not but can. Should it be like 5 to 6 psi at idle? And I could do a volume test guessing around 100 ml in min? See I got on ken co website couldn't find my models manual if I had the factory manual with my back round it would be pretty close to having a johnson tech working on this I just need that book the clymers I have is junk and doesn't tell you anything really I don't trust it I already found a couple misprints.... I guess ill call ken cook and ask them

 

[chris71167]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

got the factory manual from ken cook co. It really helps alot clearer.....but still really havnt found a PROBLEM that is causing my boat issues.
Checked gas no water contamination looks good. removed pickup tube in tank totally clean. no crud in tank neither. remove fuel tank vent. found little chrome vent had crust and was 90% blocked cleaned and reinstalled. did timing link and sync exactly according to manual. checked fuel pressure it appears i have 2 fuel pumps....combined pressure at idle 1000rpm is about 4-5psi. That a tiny bit high? also checked fule pumps screens totally clean.

So im stumped i can double check all hoses and routing. remove carbs and inspect....again check float levels... thats all i got. any help would be appreciated.

 

[chris71167]

Re: update=90 150 johnson gt runs great but wont go over 2800rpm

1. found floats to be 1/4 too low adjusted.
2. found #1 plug wire on coil pushed inside boot touching coil electrode but not over it.
3.link and sync and time per manual. noticed when timing at idle my cam follower is maxed out in the advanced and im getting 6 deg to maybe 6 1/2 i guess its ok. manual says 7 -+ 1 deg. the book shows the cam follower maxed or close to maxed out is this normal on this model. so i guess i need to just put on the water and adjust the idle screw until its idles and recheck to see if all this fixed it.