OMC 4.3 Idles great won’t accelerate

[EricV]

Ok I am getting my ass kicked on this one. Picked up my grandpas old boat that was not running and given to me. 88 four winns with OMC 4.3, motor must be newer because it doesn’t have a mechanical fuel and there is no blank off plate on block, block not machined for one. Anyways it had a bad seized valve on #6 cylinder. Pulled heads and had machine shop due a complete head job, new seals, valves, etc. I put motor back together adjusted valves etc. New exhaust flappers. New cap and rotor. Verified coil was good with my meter. Set timing to 6deg at around 650-700rpm range. Motors starts and idles great zero issues with that. Go to come off idle and accelerate and it bogs horribly. Replaced fuel pump and verified I have good fuel pressure to carb, getting avg of 5.5-6psi, same problem still bogging. Take carb (Rochester quad) apart several times find nothing wrong same problem, pull good known working Holley carb from my other boat, same problem….. I’m at a loss, verified compression on all cylinders, averaging around 150psi on all 6.

 

[Bondo]

Ok I am getting my ass kicked on this one. Picked up my grandpas old boat that was not running and given to me. 88 four winns with OMC 4.3, motor must be newer because it doesn’t have a mechanical fuel and there is no blank off plate on block, block not machined for one. Anyways it had a bad seized valve on #6 cylinder. Pulled heads and had machine shop due a complete head job, new seals, valves, etc. I put motor back together adjusted valves etc. New exhaust flappers. New cap and rotor. Verified coil was good with my meter. Set timing to 6deg at around 650-700rpm range. Motors starts and idles great zero issues with that. Go to come off idle and accelerate and it bogs horribly. Replaced fuel pump and verified I have good fuel pressure to carb, getting avg of 5.5-6psi, same problem still bogging. Take carb (Rochester quad) apart several times find nothing wrong same problem, pull good known working Holley carb from my other boat, same problem….. I’m at a loss, verified compression on all cylinders, averaging around 150psi on all 6.

Ayuh,...... Welcome Aboard,...... Did ya dig the ole remains of the ole shutters outa the downstream exhaust,..??
Pull the drive, 'n look Up the exhaust passage,.... ya might see the ole shutters,....
Just guessin' if it can't breathe out,...... it can't breathe in,......

 

[Lou C]

Yep could be that, but also on our own Four Winns, we had a rusty anti siphon valve, that did the same thing, it would start and rev in neutral just fine but would not plane out the boat. Our mechanic replaced it back in 2004 and its been fine ever since. Spring loaded valve that shuts off fuel flow if a fuel line ruptures. Its the barbed fitting that the fuel line to the tank attaches to at the tank.

PS your boat looks just like mine....200 Horizon?
One thing I did with this boat to make it easier to work on, was to get rid of the big heavy bench seat that had to be moved every time you winterize or change the oil. I replaced it with a pair of pontoon bench seats that can be easily taken out, one at at time as needed and made the big bulkhead at the rear of the boat open like a door on take-apart hinges. Much easier if you have this set up.

 

[EricV]

Ayuh,...... Welcome Aboard,...... Did ya dig the ole remains of the ole shutters outa the downstream exhaust,..??
Pull the drive, 'n look Up the exhaust passage,.... ya might see the ole shutters,....
Just guessin' if it can't breathe out,...... it can't breathe in,......

Yes I got the old ones out. Verified new ones were moving freely before reinstalling exhaust manifold. But I can’t help but wonder if they are restricting the flow, seems to be exhausting fine out the back, discharging hot water and not overheating though. Upon further evaluation with the some additional research I decided to pull distributor again and can’t believe I missed the fact the gear teeth are badly worn to about half the thickness they should be…..

 

[EricV]

Yep could be that, but also on our own Four Winns, we had a rusty anti siphon valve, that did the same thing, it would start and rev in neutral just fine but would not plane out the boat. Our mechanic replaced it back in 2004 and its been fine ever since. Spring loaded valve that shuts off fuel flow if a fuel line ruptures. Its the barbed fitting that the fuel line to the tank attaches to at the tank. View attachment 341462

PS your boat looks just like mine....200 Horizon?
One thing I did with this boat to make it easier to work on, was to get rid of the big heavy bench seat that had to be moved every time you winterize or change the oil. I replaced it with a pair of pontoon bench seats that can be easily taken out, one at at time as needed and made the big bulkhead at the rear of the boat open like a door on take-apart hinges. Much easier if you have this set up. View attachment 341463

Yeah it’s a horizon 200. She won’t even rev properly in neutral with 6psi fuel pressure at carb. Someone else mentioned the ESA to me, I checked the switches and they check out fine with my ohm meter but I’m not sure about the module they go to that’s attached to the transom.

 

[Lou C]

You want to make sure that the ESA is not on all the time. Try temporarily unplugging the ESA switches and see if it will rev properly