Johnson 150 WOT issue, maybe??

[jaxdad]

The motor - 1988 Johnson GT150, model - J150stlcca.

History - am fairly new owner to this motor that was previously a 1 owner motor, bought and serviced since new by dealer i bought it from. It was replaced as the boat owner wanted more power and stepped to a newer 200 HP motor (so ive been told by dealer.) have all receipts and paperwork from service to motor even standard winterizations, etc.. new style VRO pump, plugs, tune up and water pump installed this spring (2011)

Problem -
Initially the motor ran great, no issues at all for 5 - 6 trips out on water. Then one day after running a while it just went from 5000 RPm and running great to dropping off to about 2800-2900 rpm. checked primer bulb - firm, checked tank gas cap vent - open, and all of a sudden it jumped back up to full throttle and no more issues rest of day.
2 or 3 more trips out after this no issues.
another day it did same as above 3 times, tried to put into neutral and throttle back up, no changes, tried other fixes above with no changes. Shut motor off, fished the area with troller for couple hours, started motor back up and still not going above 2800-2900 rpm.
NO Alarms this whole time and yes it has been tested and works..

Did notice something in fuel tank that appeared to be some sort of coating peeling off from inside the tank, so this is fix we performed - New 6 gallon tank to continue testing before replacing with a larger permanent new tank, New fuel lines from tank to fuel/vro pump, new fuel filter, new primer bulb, Rebuilt all 3 carbs (dealer performed carb rebuilds), all fuel lines from pump to carbs replaced or flushed before rebuilt carbs put back on.

After all fuel system work it still from the get go (not even warmed up) will only hit about 2900 rpms. It has always idled smooth, and runs to the 2900 rpm mark great and runs at that speed great, no misses or hesitations, funny noises or anything.. just wont go above that.

was suggested to try unplugging temp sensors (1 per head) and ground the engine side of wire to test alarm, and no problem -key on, wire grounded, alarm went off immediately with each sensor tested. Did notice that at the back of motor looking forward the left side temp sensor wire ran down behind coil pack and was brittle, insulation gone, and wires corroded - just found it, so havent had time to fix.. but could this be the culprit??

other than these temp sensors, i am at a loss of what else to check or replace.. really need suggestions as a big tournament is coming and i need it ready ASAP..

thanks, and sorry so long on the info.

 

[emdsapmgr]

Re: Johnson 150 WOT issue, maybe??

Possible you have an ignition part which is in the process of failing. You may find one or two plugs are misfiring or not firing at all. When the engine starts to act up, put an inductive timing light on each plugwire and check for spark in the flashes of the gun. You don't have an rpm limiter on that ignition system in case of an overheat. But you do have two identical power packs-one for each head. If you find a spark issue, you can swap the packs for testing purposes.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

ok, thanks, i'll try the timing light / spark plug test tomorrow along with the disconnecting of the temperature sensors.. i'll let you know how it goes.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

OK so it is running fine now and im boggled by what it could be, must have been the damaged wire to the temperature sensor. Yesterday we covered the temperature sensor wires with electrical tape for the test, unplugged temperature sensors, and changed spark plugs because i had an extra set. so we took it out for the on water test, with inductive timing light in hand. While testing it only "bogged" down or failed to go above 3000 rpm once, and that was at the very beginning of the test at the inital start up and placement into gear. The whole "bogged" down issue lasted maybe 15 seconds, not even time for me to get the hood off to hook up the timing light. After that it took off and never missed a beat, ran better than ever. So we ran it a while with temp sensors unhooked, then hooked one up - no alarm, ran a while longer, and hooked second temp sensor up - no alarm. Finished on water test without fail or issue and no problems, through a complete 6 gallon tank of fuel, inlcuding WOT, idling, shutting off and restarting, etc.. . Not sure what fix was but believe maybe frayed damaged temp sensor wires.. but really unsure since plugs replaced at the same time..
thanks for the help, and hope this helps someone else.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

here we go again..
After having what we thought was a successful fix and test the other day, last night the same issue showed up again..

we ran the motor for about 2 miles to our fishing hole and no issues, fished for a hour or so, then started motor to go to the next fishing place and from the get go it would not go above 3000 rpm.. lifted hood, unplugged temp sensor wires , and it ran great for about 30 seconds, and went back to 3000 rpm..

the whole time it has been doing this we have NO buzzer/alarm warning at all. It has been checked also and works. some days it happens after motor has warmed to operating temps, and other days it does it straight off the trailer..

We are checking ignition components and timing today.. Any other ideas??
thanks.

 

[Exotic4x4]

Re: Johnson 150 WOT issue, maybe??

Cracked coil pack somewhere? Something sounds like its getting warm and failing I used a can of spray freeze on my old 115 Johnson to diagnose I'm not sure if that helps but have u had a timing light on at all when your motor bogs? This will tell you if and when your losing.a.cylinder(s) try that out put your motor in the fake lake and get the timing light on and test your spark

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

Thanks Redfx4.. was planning on trying that the other day and had inductive timing light ready and it would not do it so i could test them.. Maybe i should just leave the timing light in the boat if that stops it from acting up.. lol.

what has me confused is that it will do it sometimes when cold, and others after it warms up, sometimes you can shut it off and restart and its fine, other days you can run it all day and never once have an issue..

 

[reddogg]

Re: Johnson 150 WOT issue, maybe??

God, I hate problems like that, enough to drive a man crazy If a part is going to fail, i like them to just fail, makes it soooo much easier to troubleshoot. I think it's an ignition problem. Good luck to ya man.

Red

 

[clanton]

Re: Johnson 150 WOT issue, maybe??

Check flywheel magnets

Check stator output. easy test boat in water on plane full throttle, bump up trim button, if RPMs drop by 300 stator is bad.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

Clanton,
thanks for the advice, i'll double check it.. but i know the stator and timing base was all replaced new in last year and when regulator/rectifier replaced earlier this year all that under flywheel was checked again and was very clean and no magnets found loose.. I also normally watch the RPMs when trimming the motor because i was warned to never take the motor over 5000 RPM when in gear running in water, have never noticed a drop in RPM at all..

although that brings up another question.. what would be the max RPM's for this motor? and what should be a RPM to not run boat higher than? Currently when boat runs great and does not bog down, it runs exactly on 5000 RPM at WOT, has great power, but curious if this is where it should run or should it be faster for optimum fuel efficiency and motor life. I see where some talk about similar motors running at 5500 RPM with a max around 5800. It has a 4 blade stainless prop with the words "Shooter 13 1/2 x 22pp" stamped on it..

Im going to test ignition switch and wiring also tomorrow. I have a 6 foot test switch and plug to bypass the one in control box.

thanks again everyone.

 

[clanton]

Re: Johnson 150 WOT issue, maybe??

OEM manual calls for 5500 rpms.
One more easy test check voltage at primary side of coil, all six should be same.

 

[emdsapmgr]

Re: Johnson 150 WOT issue, maybe??

Your engine is a 150S model. That makes it an XP/GT engine. Those are the high perf engines which put out up to 10% more than the labeled 150 hp. That engine was rated to run up to 5500. That engine will make good hp up over 5500, close to 5700 or so. The rev limiter will kick in at 5800.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

here are my test results from this morning.. i may have found the problem..

backed the boat into the water and from the get go it was idling rough (this was a first).. used the idle screw to get to 900-1000 rpm idle, and all smoothed out. When using the fast idle lever when initial cold start motor would idle up fine, but when shut off it would idle around 500-600 and rough. Once idled up to 900 or so i began the testing. I did notice a couple times before i could get any testing done the motor jumped up twice to 2000 RPM for a split second and fell back down, just at idle and in neutral.

1st test - put in gear and throttle up. Result - throttled up smooth, but stopped at 3000 and wouldn't go higher. This result gave me the green light i needed to check further (FINALLY!!! screwing up while i had test equipment handy).

2nd test - Inductive timing light all spark plug wires.
result - (looking as if standing behind motor)
Left side top and middle cylinder had spark and even flash of timing light. bottom cylinder - NOTHING.
Right Side - All sparked and flashed good and even, appeared no misses or uneven flashing.
back to left side again and found NO SPARK or timing light flashes on any cylinder, test Right (to make sure light was working) and got steady flashes on right.
back to left nothing, recheck right and got steady flashes so no timing light issue.

test #3 - Voltage at incoming wire to each coil.
right side no issue, all even voltage.
left side had issues - top and middle coil had .004 volts, and bottom coil had 8.6 volts.

test #4 - replace ignition wiring from control with 6 foot (red plug) ignition switch harness, to bypass wiring from controls to engine.
result - No change. When this test harness is on everything worked the same as before without it. So i would guess it is safe to say the ignition harness and switch is safe from the control box area.

so i am about to get a new ignition module and replace the left side to see if issues clear up for good this time.. if anyone has any other suggestions please feel free to share.

(clanton - couldnt check the RPM drop test you suggested for stator issue, due to boat not running good enough to even get on plane.. But manufacture date on stator and timing base harnesses shows late 2010 dates, aug and oct)

thanks everyone.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

Your engine is a 150S model. That makes it an XP/GT engine. Those are the high perf engines which put out up to 10% more than the labeled 150 hp. That engine was rated to run up to 5500. That engine will make good hp up over 5500, close to 5700 or so. The rev limiter will kick in at 5800.

Yes it is a 150 GT v6 VRO.. sorry thought i listed it at top..
would the 4 blade stainless 22 pitch prop be the reason for the max of 5000 to 5100 RPM at WOT versus the 5500 or so?? i am not sure what "stock" should have been to get OEM figures, therefore i am unable to figure if the 22 pitch 4 blade would drop or raise the WOT RPM from OEM recommendations.. Once i get this WOT issue fixed i want to try to get max HP, performance, and fuel efficiency out of it, even if i need to buy a new prop.. thanks!

 

[wilde1j]

Re: Johnson 150 WOT issue, maybe??

You should have used a spark tester like this with the air gap set at 7/16". Spark should be sharp and blue.



Your motor should turn 5800 RPM @ WOT if propped and set up right. But don't mess with props until it's running right.

 

[emdsapmgr]

Re: Johnson 150 WOT issue, maybe??

A 22 pitch 4 blade is not an unusual prop pitch for an XP/GT. Maybe you have the engine mounted too low on the transom. If it is the correct height, you may want to try a 21 (or even a 19) to get the rpm's up a little. To me, you are lugging the engine at 5000. You gain 150 rpm when you go down in prop pitch, like from a 22 to a 21. When you say you are replacing the ignition module, I am assuming you mean the power pack. Likely that will cure your problem.

 

[hidef]

Re: Johnson 150 WOT issue, maybe??

You had all the cylinders sparking on one bank and nothing on the other bank. It could be one of the following;

1)The kill circuit for that bank is acting up disconnect the yellow black wire for the bank that isn't firing.
2) You have a bad stator you need to switch the stator leads around on the power pack and see if spark follows.
3) Disconnect voltage reg/rectifier see if spark returns
4) Bad power pack.

Seeing as you have replaced 2, 3 I think you have kill switch wire that is grounding out on you while running your power back could be failing but I would make sure the wires are good first. When you had both heat sensors disconnected you might have managed to move the kill wire away from what it was grounding on. Carefully check all of your wiring.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

more confusion... when i returned home i thought i would check the power pack again, and switch sides to see if no spark issue changed sides with the pack.. Hooked up to the garden hose (figured since i was going above idle for these tests it would be ok).. Started motor and it idled smooth at 2000 RPM!! (the in water tests with rough running and half cylinders firing needed adjustment to stay at 900) so i used idle screw to back down to around 900-1000 RPM.. and guess what - Spark on ALL cylinders using both the inductive timing light, and a spark gap tester set at 7/16".. with gap tester all sparks were bright (in daylight so hard to say white or blue, etc..) but bright enough to see it was sparking good on all cylinders.. Again tried test ignition switch lead and no changes there either...

i really hate this on/off issue, really wish whatever it is would just fail so i can track it down and replace it.. New Pack was ordered before this latest test, so maybe when it comes in ill go ahead and replace anyway, if not bad ill have a spare...

 

[hidef]

Re: Johnson 150 WOT issue, maybe??

Check your wires under the cowl. Make sure all of your wires good and the connections are clean and tight. You are chasing an intermittent problem do not rule out the wiring and the ignition switch this smells like the kill circuit is not working right.

 

[jaxdad]

Re: Johnson 150 WOT issue, maybe??

Check your wires under the cowl. Make sure all of your wires good and the connections are clean and tight. You are chasing an intermittent problem do not rule out the wiring and the ignition switch this smells like the kill circuit is not working right.

Thanks, and chasing the intermittent problem sucks.. im going to put the boat back in the water and "if" it will mess up im gonna try to eliminate the kill circuit by disconnecting the black/yellow wire at the pack..

I have a ignition circuit with key switch that i use to test with.. it is a regular harness (red plug style) with a good ignition key setup, it gets plugged into engine harness under cowl to bypass the ignition circuit from the control box.. each time i hook it up there is no change in performance, if its running bad at time of switch it keeps running bad, if it is running good it keeps running good.. so i believe the ignition circuit from controls to engine are good as there are no changes from either circuit..
as for engine harness wires and connections i have checked them all to make sure a pin has not been pushed out or something simple, as well as inspected for missing insulation or grounding issue and if found fixed them (ie - temp sensor wires bare under coils). also made sure all clips or retainers are in place on connections to keep them together.. but i will recheck, never know what i might have overlooked..

any help is appreciated the sooner i track this down the better.. thanks again.