OMC Cobra 4.3L Idles but no RPMs

[jbbumper]

I have a 88 OMC Cobra with a 4.3L engine. It overheated first time out this year. I replaced the water pump impeller and housing. I have checked the compression and all cylinders are at 150 to 160. I have checked the oil for water and didn't have any in it. When I start it, it runs very rough and won't throttle up at all. I have replaced the plugs, points, cap and rotor. Any other suggestions?
Thanks

 

[180shabah]

Re: OMC Cobra 4.3L Idles but no RPMs

How about fuel, fuel system and carb?

 

[jbbumper]

Re: OMC Cobra 4.3L Idles but no RPMs

Thanks for the reply. Sorry forgot to mention, Yes the filter canister and the inline filter has been replaced. I think I found the problem. I moved the shifter a couple times and it started running great. If I rev it a little out of forward it runs fine but when I move back to idle it does it again. I can move the fork that controls the position of the sensor ( don't now it's exact name) and it runs fine again. Also it shifts to forward and rpms up but won't shift to reverse. If I disconnect it, the shifter and cables are smooth.
So I'm thinking it needs some sort of adjustment in the shifter cable. It seems like there is a lot of play in the plastic bushing that it pivots on so It may need replacing.