Low power under load at 1/2 or more throttle

1980 175HP OB having trouble making power and running smoothly under load.

Did the usual preliminary tests. Compression is at 90 PSI on all six cylinders. Strong blue spark even at large gaps on the spark tester. Then rebuilt the carbs, adjusted the floats, sync'ed and linked the carbs and adjusted the high and low speed timing.

Ive got new spark plugs and fresh gas. New fuel lines and checked that fuel tank vents. Also squeezing the primer bulb doesnt help.

I still had the same problem.

I pulled out the multimeter and checked all the electronic components according to the manuals specs and everything checks out ok.

I'm really getting discouraged here and really close to dumping the motor for a 4-stoke.

Please help!

Re: Low power under load at 1/2 or more throttle

Anyone got any ideas?

Re: Low power under load at 1/2 or more throttle

Did you happen to check the stator in your testing? The symptoms you are describing are an indication that your stator may be shot. There are low and high speed windings on it, and the windings on the high side may have failed. If you do a search on the forums you should find plenty of posts with similar issues.

Re: Low power under load at 1/2 or more throttle

I agree it's probably the stator but just for grins, check the oil pump linkage to make sure that something isn't binding and check the advance linkage for the same thing. The oil pump linkage will keep you from WOT but the advance keeps going and will make it run rough. If its the advance linkage you might not have enough advance to support the air/fuel mix at full throttle.

On one of mine the advance worked fine with the throttle cable off but the side torque of the cable caused it to bind against the fuel hose. Looked good during setup but ran lousy on the water. You can imagine how many times I scratched my head over that one.

If those check out o.k. then get to work on the stator.

Re: Low power under load at 1/2 or more throttle

Thanks for the reply.

I checked the stator again on my multimeter and all of the readings fall in the appropriate scale value according to my manual.

After doing some searching on bad stator symptoms It just got me more confused and now has me thinking its a switchbox problem.

Just to give more info on the engine's current running condition:

It starts and idles perfect.
Under 2000 RPM runs normal sounds good.
Give it 1/2 or more throttle and the engine stumbles and struggles to plane. Sometimes it will eventually plane and turn 4300 RPM but sounds like junk and missing. Other times (usually when warm) it will bog out and only turn 3000 RPMs and will not plane also running like crap and sounds like its missing.

Ive also read that some of the resistance figures on the manual mean nothing to the actual condition of the ignition components. Is there another accurate way to test these parts before I go on a wild goose chase trying to fix this problem?

Re: Low power under load at 1/2 or more throttle

Called the tech support over at CDI electronics and they were able to assist me on some troubleshooting techniques for the ignition system.

Also these might help:
http://www.cdielectronics.com/Portals/0/installsheet/114-7778.pdf
http://www.cdielectronics.com/Portals/0/installsheet/174-5456.pdf

Like the previous posts I was advised to change out my stator.

It was also recommended to me to change my spark plugs for gap-able plugs.
So I'm going to try this out and after I change the stator and if the problem still persist the only thing left is the switchboxes.

Re: Low power under load at 1/2 or more throttle

The engine now runs great.

I ended up changing the stator, 1 switchbox, 3 coils, and spark plugs. However,
A CDI tech advised me to remove my Black box, which is the idle stabilizer which could be causing some top end issues. I removed it and the boat now runs much better with throttle but now suffers at idle speeds and dies. I tried putting it back on and sure enough i coudnt rev past 4K RPM but my idle was stable again.

My manual states the black box either works or doesnt. It obviously works so I really don't know what I should do at this point.

Any suggestions? bump up idle speed?