Johnson 60 sluggish and stuttering at WOT

[Kruegs35]

Still struggling with this issue. I tried choking(priming) the engine at WOT and there was no improvement, so I am assuming it is not a fuel issue. I have bought a service manual and checked the temp sensor diode and resistance on the coils. Everything seems to check out. The issue is so consistent that I want to believe the power pack is going into SLOW mode. I replaced the power pack again and that did not solve the problem. I have also run without having the temp sensor connected at all and that didn't work. I do not have a peak voltage meter or a timing light, so I know there are some things I have not been able to check. I just got a tach, but I won't have time to take the boat out today. Does anyone have any more suggestions?

 

[racerone]

Remove cylinder head for inspection.---New head gasket is cheap compared to other electrical goodies and guessing.

 

[Kruegs35]

Removed the head and everything looks good.

 

[Kruegs35]

Bought a tach and the RPMs are maxing out at 3800.

 

[KILNK]

I had a 1987 60 hp do the same thing. The third time I rebuilt the carburetor so soaked them for the weekend took them to work and blew them out with compressed air. I found a passage blocked.

Put it back together and it ran great.

 

[Kruegs35]

KILNK, what did you soak them in?

 

[jakedaawg]

Open air gap spark check on a spark checker that will do all three at once. Manually advance timer base fully. Have all plugs removed. If you notice weak spark on one got to DVA. Disconnect the amphenol connector. Jump the leads. Take DVA reading And compare manual. On the one with weak spark test DVA with that coil lead jumped and with it just coming from pack. If in speck on first case replace coil. If in speck on second case replace pack. Hint, it's prolly the pack.

 

[Faztbullet]

Check the flywheel timing, the bad one I had the timing would not advance past 10 degrees at WOT

 

[Kruegs35]

ok, I am officially out of ideas. Just to recap, the motor will not go over 3800 rpm and starts to shutter at WOT and I cannot get up on plane. Here is what I have done:

Rebuilt carbs
Replaced fuel pump
Replaced fuel/water filter
Replaced spark plugs
Replaced power pack
Replaced stator
Replaced rectifier
Checked compression
Checked and replaced headgasket (original was fine though)
Checked resistance of coils
Checked timing at WOT
Checked spark gap
Pushed primer and squeezed bulb at WOT with no change

I have no idea what is left to check.

 

[flyingscott]

If you have S.L.O.W mode on that motor and the VRO is still working check the diode in the wiring harness you will need a diode checker.

 

[Kruegs35]

I have checked the diode and wouldn't my rpm max out at 2500 if it were in SLOW?

 

[Kruegs35]

I've also checked the temp sensor.

 

[Kruegs35]

I have been assuming it is an electric issue because when I push the choke(primer) at WOT, the engine bogs down. Also squeezing the primer bulb at WOT does nothing. How accurate is this test? Has anyone been fooled by this test and still ended having a fuel issue?

 

[jakedaawg]

Did you ever pull the flywheel and check the magnets? One could have broke free and moved.

 

[oldboat1]

or check spark with a spark tester? need an open air adjustable tester ($10 or so) -- should see about a half inch using the tester. This is a test to see if the ignition is producing enough to fire the plugs -- not a test of plugs or plug gap. Additionally, #14 would give you a dropped cylinder test, not a timing test -- checking to see if spark is lost at higher rpms, heated ignition parts, etc. Another way is to pull off plug boots one by one. If you get no change (sputtering, lower rpms, stalling), that cylinder is not producing (dropping out).

 

[Kruegs35]

I did pull the flywheel when I replaced the stator. All of the magnets looks fine. I also did a spark test with a half inch gap. I only check the timing with the first cylinder, so I will have to try again on the other cylinders.

 

[jakedaawg]

I did pull the flywheel when I replaced the stator. All of the magnets looks fine. I also did a spark test with a half inch gap. I only check the timing with the first cylinder, so I will have to try again on the other cylinders.

To check timing on the other cylinders you will need to.make your own marks on the flywheel 120 * apart from tdc for #1

 

[Kruegs35]

I went ahead and just replaced all three coils. No increase in RPM, but it seems to shake less and have a deeper sound at WOT. Does that mean anything to anyone?

 

[Kruegs35]

Mystery Solved! Cleaned the carbon coating the top of the pistons and she runs great!

 

[whiteghost06]

Mystery Solved! Cleaned the carbon coating the top of the pistons and she runs great!

How did you clean them I have a 93 150 that's doing the exact same thing as your and I've replace pretty much all the same parts you have and still won't go past 3k