84 Mariner 90hp Bogging Down

[muskrat787]

I have a 1984 Mariner 90 hp that cuts out when I try to throttle up. Carbs have been rebuilt, all fuel line on the motor has been changed to barrier hose, the fuel pump has been rebuilt , the rectifier has been replaced and I am using a brand new portable fuel tank. The bulb stays hard through any running. Compression on all six cylinders is 135-140.
I can throttle up in neutral with no issues but under load the motor cuts out immediately upon throttle up. No hesitation, no lag. As soon as I throw the throttle forward from idle the motor starts bogging down. Can't get more than 1500 to 1800 rpms max.
Any ideas would be greatly appreciated as I would like to try to resolve the problem before winter really sets in.
Thanks in advance for any suggestions.
George.

 

[racerone]

Open the low speed mixture needles 1/8 turn at a time and test again.---Likely the problem will be solved after a couple of tries.

 

[muskrat787]

I will give that a shot but I don't have high hopes. Motor ran fine for a while after all of the work that I done to it before it developed this issue.

 

[racerone]

Sorry , but it is a classic symptom for these engines to idle nicely when low speed needles are adjusted for a smooth idle.---Then they stumble on rapid accelleration.---Let me count how many times we have seen this !

 

[Chris1956]

Racer...You cannot count that high!

 

[muskrat787]

I will try it next week and let you know how it worked out. Thanks.

 

[muskrat787]

Tried adjusting the carbs and no luck. So I took my timing light for a boat ride. All cylinders fire fine at idle. Checked each cylinder one at a time during throttle up. All cylinders checked ok EXCEPT #3. Every time I went to full throttle #3 would stop firing. So I took the wires off of #3 coil and #2 coil and switched them including the plug wires. Still had problem with #3 losing fire at throttle up. I have already changed the switch box so what could be causing this? Stator? Trigger?
Thanks,
George.

 

[racerone]

Swap the 2 switch boxes.---See what happens to spark.

 

[muskrat787]

I have already replaced both switch boxes.

 

[muskrat787]

Replaced the trigger but it did not fix the problem. So I had seen that rectifiers can cause weird problems. Hadn't looked at that because I changed it back in the spring. Since I still had #3 losing fire at WOT I figured what the hell, it's worth a shot. So I disconnected the rectifier and the problem went away. Motor ran like a champ. So what now? Stator or rectifier?

 

[Iceman66]

What kind of stator do you have? How many amps does it deliever?
Is it the original "wrapped in" or a "open" one from aftermarket that cools better ?

If you have the one from CDI-electronics, its possible you need a special rectifier/regulator that they produce,all depending of amps.
Its possible the original rectifier is not the right one to use then.

You can check all values with a DVA-adapter to a standard multimeter, using the CDI-electronics ignition troubleshooting guide(page 83 and 84).
http://issuu.com/cdielectronics/doc...t.xml&backgroundColor=000000&showFlipBtn=true

 

[muskrat787]

Iceman66,
Thanks for your reply. I have the original type stator that is fully wrapped. I have a DVA adapter and I have done every test that CDI has listed and all checks good at idle speeds. Cannot get anyone trustworthy to go on the boat with me to do the high speed tests. Ohmed out the rectifier again today and it looks good. Could my problem be the stator or possibly the tach?

 

[muskrat787]

Ran the motor today with the tach disconnected and the stator hooked up. Ran horrible so I can assume that the tach is not the problem.

 

[Iceman66]

Get yourselve some multimeter test-leads that goes through wire isolation and "hooks"on to them, then you can do the
lowspeed and highspeed test by your selve even out at sea..

Does the engine run like it should with the rectifier disconnected, you should not only do an ohm-test on rectifier, but do the complete rectifier test described in
a service manual.(seloc or Clymer)
My guess is that you have a stator problem, but only a complete stator test can tell fore sure.