Bog/hesitation 5.0

[JollyRoger87]

Hey guys. Have a slight issue my 92 four winns 190 horizon. It has a 5.0 omc cobra, with a Holley 2 barrel, and electronic ignition.

About a month ago, it left us stranded on the water. The motor wouldn't run under load and had a difficult time starting at all. Brought it back home, changed everything ignition related, one thing at a time, and found the culprit to be the coil. Runs fine now, except for one thing:
In the yard on muffs, it hesitates consistently at about 2800 rpms. On the water with a load on the engine, when it gets to this point, you have to baby the throttle to keep it from stalling.

Everything else seems fine, cruising along at part throttle away from the dock, no problem. WOT on the lake no problem. It's just this one point in the RPM band that gives you trouble. Any thoughts?

 

[skippy2235]

What plugs did you use. (BOSH suck)
Use OEM plugs only.

 

[Offrddrver]

Welcome to the site J.R.87. You'll find several posts related to this kind of issue, and on 1992 Four Winns 5.0L OMC.C. units.

By any chance do you know your model number? If so, that often helps with troubleshooting.
It should be one of the following: (My number was found on the valve cover on the Port side of the motor.)

• Model 502APLAMH
• Model 502APLAMK
• Model 502APRAMH
• Model 502APRAMK
• Model 502BPRAMH
• Model 502BPRAMK

Next, you stated you changed everything related to the ignition.
What electronic sensor did you go with inside the distributor? (Hotspark, Pertronix Ignitor, Pertronix Ignitor II, other)

Possible fuel starvation to the carb or bowl.
When you "baby the throttle" I presume you mean throttle up/down/up/down to keep it running. This may be pushing fuel by way of the accelerator pump which may be giving it just enough gas to keep running, then once the RPM's come up the fuel pump is delivering more fuel.

My experience with this:
1. Fuel carb bowl/float issue due to white residue buildup in the bowl causing the float to stick. Had troubles at lower RPM, horrible holeshot, but once running up to speed it seemed fine. (Cleaned and rebuilt the carb fixed this issue.)

2. Prestolite distributor sensor failed. It had an internal positive voltage shorted to ground. (I replace the original Prestolite sensor and the original coil with Pertronix Ignitor II sensor and Pertronix Flamethrower II coil. I also had to add the Diode + Resistor pack between the coil and the ESA module. (Runs great now, maybe better than ever.) (I'm looking at a CDI ESA module so I can get rid of the Diode/Resistor pack in the future.)
2a. I knew this was an electrical issue also, because at W.O.T. if I trimmed UP or DOWN the RPM's would "drop/miss" as long as the button was held. Once the trim button was released W.O.T. RPM's were good again.

The last one I've only read about, but have seen it on a couple web sites.....

3. Fuel starvation due to the safety anti-siphon valve sticking (check valve) located at the top of your fuel tank between the gas tank pickup and the water/fuel separator filter. At low RPM the pump has trouble pulling fuel past the check ball, but at higher RPM you can run fine.

Hope that sparks an idea for you to check.

For me, the most consistent issue that sounded like your issue was item 2. That had the same consistent bad results every time. My fuel problems were not so consistent, but did appear similar.

As always, check the simple things if you haven't already....clean ground terminals at block and battery, clean positive terminals, check for loose ground/positive wires and connectors.

Best of luck

Offrddrver

 

[Offrddrver]

Sorry, one more thought.... If you have the Prestolite distributor and it is my same setup, have you checked your advance weights/springs are moving freely? I'm not sure how consistent this would be, but maybe the weights are sticking at lower RPM and then free up and open/advance properly when the higher RPM's get moving.

Check that your advance is moving/advancing through those lower RPM ranges with a timing light. (don't high rev on muffs though)

Offrddrver