92 150 fast strike loss of WOT under load

[Cmill0603]

Okay, it is time to get some extra help on my 1992 Johnson Evinrude fast strike 150 hp. My current problem is I have a loss of WOT when the prop is under a load. The motor runs great in idle. I can leave the engine running with water ears and you wouldn't know anything is wrong. I am able to idle around the lake without any issues. Once I take off to plane out, there is a hard stop at 3000 rpm and the engine sounds like it is bogging down.

I have replaced almost everything and two boat mechanics have had this. I am close to $3000 in the hole so the problem has to be something small...

Here is the history...
I was having a loss of power when pulling on the trailer and the motor was missing at high end. The first mechanic replaced my fuel pump and said that it was fixed. It wasn't, carb bowls were warped and fuel was leaking. I Rebuilt the carbs and cleaned them Replaced powerpack/ coils/plugs/ spark plug wires. Still was having an issue. Second mechanic replaced temp switches and it fixed my loss of power pulling on trailer. He put in new stator and tried a CDI, OEM and Sierra powerpack.

I have done a few things since but I still am having a loss of WOT. I have blown air through all fuel lines.

The oil pump is disconnected. I mix my own oil.

Any advice anyone can give, it is greatly appreciated.

Thanks,
Cmill

 

[ezmobee]

Sounds like it's losing spark on a cylinder or two. Currently chasing the same issue on my 90HP. I've swapped new coils and a known good powerpack around on mine to no affect. Next I'm thinking timer base/trigger.

 

[Cmill0603]

I've hooked up a spark plug tester and have fire at each plug at idle. I haven't had the tester hooked up while trying to plane. Think I could be losing fire at high end?

 

[flyingscott]

Have you done a compression test? Have you done an open air test to make sure the spark jumps 7/16". Has anyone looked at the OIS sensor. Is the S.L.O.W mode engaging, I believe your motor has that.

 

[Faztbullet]

It sounds like it going into S.L.O.W, does it have the new grey wires?? Have actual temp been tested as could be bad t-stat tripping S.L.O.W

 

[Cmill0603]

Compression test checks out fine. ~90 psi and all cylinders are +/- 5psi. I have not done an open air test, only hooked up the plug to inline light tester. The optical sensor was supposedly replaced by the second mechanic.
As for the S.L.O.W. I am assuming that is when the engine is overheated and the temp sensors are not allowing high end fire. I have disconnected the wires on both the starboard and the port sides and the loss of WOT still occurred. This was my initial thought as well. No horn sounds. If there is another way to test the temp switches, please share and I will make it happen.

Thanks for all the insight!

 

[jakedaawg]

I believe the fuel restriction sensor will also enable slow on those.

 

[Fed]

Is the horn connected & does it work? A fuel restriction would explain everything.

 

[racerone]

Replacing parts gets expensive.---Not the best way to repair motors.----Try another compression tester as those values appear to be low.-----Myself I would remove a cylinder head to inspect cylinder walls.

 

[Cmill0603]

I have never heard an alarm nor have I tested it. I will check on the alarm and also check for fuel restrictions.
I will keep y'all updated. Thanks again for the tips.

 

[Cmill0603]

I am assuming that the fuel restriction switch is also called a vacuum switch. This is the sensor that is inline at the fuel reservoir before the diaphragm on the fuel pump. I changed the vacuum switch and no changes in the issue. I tried running the boat without the switch connected and still no change. Besides the temp and vacuum switches, is there anything else that could put the boat into SLOW mode?

 

[bob johnson]

do you have temperature gauge on the boat? I thought slow limited itself at 2500 rpm..... are the head too hot to touch once it hits 3000 rpm and stalls there?

bob

 

[Cmill0603]

After I let the boat idle for a few mins each head is hot to the touch. You can touch for a second or two. I do not have a temp gauge on the boat.
If I am hitting 3000rpm's would you suggest that the issue isn't slow mode?

 

[bob johnson]

After I let the boat idle for a few mins each head is hot to the touch. You can touch for a second or two. I do not have a temp gauge on the boat.
If I am hitting 3000rpm's would you suggest that the issue isn't slow mode?

well you said your issue was at 3000 rpm...id suggest getting to that rpm max for a little bit and then throttling down and touching the head, or better yet use a infared thermometer!!! to check how hot they are getting.. if you can hold you hand on the head for 2 seconds...then it is no more than 180 degrees id guess..... the danger zone is over 200 degrees!! you overheat alarm wont go off until you reach 240 degrees!!!!!!!!!!!....id call that serious temperatures....and damage is being done in my view at those temps... my manuals say SLOW limits the rpms to 2500......ive only experienced it once and it was about 2500 rpm!!!!!!!!! good luck

bob

 

[TLL]

If it was SLOW kicking in, as you pushed the throttle lever to try and accelerate past 2500-3000 rpm, the motor would start running like crap and jumping around. Does yours run smooth at the 3000 rpm? My thinking is still spark related. Check the wiring connectors that plug into the top of the power pack, inspect the plugs carefully, the metal sockets love to push out of the plastic body and cause lose of spark.

 

[Cmill0603]

I ended up taking the boat to another mechanic and he found that when I replaced my carb bowls, I didn't transfer the high speed jet from the old bowls to the new bowls. (Duhhh!)in my defense, these are hidden behind the drain plug..
The boat now runs great for about 20 mins. After about 20 mins, the boat will not start very easily. I had to manually choke and open the throttle plates just to get back to the landing. The boat also sneezes a lot. Any suggestions on what to do now?

 

[Speakrdude]

Don't feel bad. I did the same thing. Threw out the old bowls with the little valves still in them.... duh.... Replaced ran great, for a while. Now a diff problem.