1995 OMC Cobra v-6 will not rev out under load

[ScottinAZ]

ok, finally got the '95 Four Winns (4.3 chevy with an SX in drag hanging on the transom) off the dock yesterday, only to find out it WILL NOT rev past about 1500 rpm in gear. In neutral it revs out fine..... so something is amiss in the engine department. (Prop is the standard 14.5x21 pitch it came with, and is specced for). Pulled plugs this morning, and they are still very new looking, so no real help there, (not fuel washed or black in any way, stark white from being new more than anything else. all the runtime this engine has on these plugs is about 20 minutes on the hose, and about an hour idling around when it wouldnt rev out) Did a compression test on the engine and have 155-160 on all holes, so I dont believe it to be an "internal engine" issue causing the problem.

this leads me to believe that it is something with the carburetor (gone through, but with chinesium kit) or the distributor. When I redid the heads earlier this year, I did check the timing with the shunt, and its set to spec, but this performance leads me to believe the module may not be advancing.

What are the odds of the module being crap, and not advancing? Its the Delco small diameter HEI with vertical posts on the cap. Or is it likely something in the carburetor causing issues.... its a flat out DOG under load, and I really want it working right this year if possible.

 

[Bt Doctur]

firing order correct? 1,6,5,4,3,2

 

[Scott Danforth]

Look at the fuel system

Look to make sure ethe flappers are not plugging the exhaust

Motor will rev running on only 2 cylinders

 

[ScottinAZ]

firing order correct? 1,6,5,4,3,2

yes. firing order is correct


ok, Ill admit... I went and checked AGAIN.... I had 4 and 6 reversed.... that will cause an issue.... Ill report back once I fire it up again... It should run MUCH better now both on muffs and in the water.... I have to wait for another water test, I kind of destroyed the fuel filter checking it for water and debris... that bugger was on tight.... Jungle Webiste to the rescue......

 

[ScottinAZ]

Look at the fuel system

Look to make sure ethe flappers are not plugging the exhaust

Motor will rev running on only 2 cylinders

Ill double check the fuel system. Flappers I would not think are an issue. I have plenty of evidence of exhaust coming out the back of the boat both on shore and in the water.

Engine runs "great" at idle and up to about 1500 rpm, then it falls flat on its face. Fuel pump is an electrical, and is supplying fuel to the carb, Ill pull and check the fuel filter to be sure it isnt full of water or just full of garbage... its probably due for a change anyway.


see above post... I had 4/6 backwards.... after checking about 15 times too.... fuel filter was good clean fuel. No water and no phase separation (no such thing as ethanol free in my AO... Stabil to the rescue, I put some in with each tankful, and then burn it within a month or so....) tanks get drained at the end of the season in all boats and burned in the Tahoe.....

 

[ScottinAZ]

aaarrrrgghhhhhh... seems to be a case of "maintained by moron"..... swapped 4/6 plug wires back to where they are supposed to be, and lo and behold the engine idles and runs much better on the hose at least. (yes, I had checked it before, but it still eluded me.....) Before it was a little lumpy, but I attributed that to just needing a good "on the water" tune.... now you can balance a quarter on edge on the flame arrestor.... did some adjustments on the carbie, and I have it idling at 900 or so (on the hose) ill set it for good at a water test (650-700ish rpm). Confirmed that the distributor timing IS adjusting with the timing light ( shoot the light at the balancer and confirm that the mark "moves"..... ). now to get a new fuel filter that isnt all dented to hell (possible leak risk, but good enough for "shore testing" with the cover off..... any fumes or spilled fuel will dissipate over the next few weeks....)

 

[ScottinAZ]

well, lets put a pin in this one. Took the boat out for a water test this morning after swapping the plug wires and replacing the fuel filter. The boat now has NO ISSUES with power. comes on plane nicely, and had it up to about 40 mph according to the speedo. Now time to take care of the cosmetic issues.....