kwoolard
Chief Petty Officer
- Joined
- Feb 9, 2003
- Messages
- 420
Boat: 1999 - 235WA Cuddy Cabin Sea Pro
Engine: 5.7L Mercruiser - 250hp, 2 Barrel Mercarb, Thunderbolt 5 Ignition
SternDrive: Alpha Gen II
Last year I rebuilt my carburetor, replaced rotor, cap and plugs during a tune-up. Engine runs great at idle and throughout the rpm range with a slight vibration in engine at around 2000 rpms but is smooth outside that rpm. I am running a 15.25 x 15 prop and with 5 people on board and full gas tank I am taching 4200-4300 rpms. I know I should be around 4400-4800 and would like to prop it in that range with the load I described above for my offshore fishing trips.
Original owner of the boat had a 19" prop and I was able to get 3900-4000 rpms at WOT, so I switched to a 15" prop that I had on hand thinking that would definitely get me in the range.
I currenlty have a rich idle mixture because as I'm trolling I can smell fuel in the exhaust and after putting the boat back on the trailer I have a soot line on the transom. The idle screw is at 1.5 turns out from seat, which I thought is a pretty good starting point. I haven't tinkered with that yet.
Just wondering if my problem of not reaching WOT could be my rich idle carb mixture. I don't have a miss in the ignition that I can tell, the engine idles and accelerates great. I figured if I had a cylinder misfiriing I would be able to hear it or see my rpms flucuating a little.
Vacuum readings are good, I need to run a compression test, but that requires me to remove my exhaust manifolds due to the limited engine access (BAD Sea Pro design). I figured I would be able to see a weak cylinder or valve in the vacuum test, and I didn't.
I just feel this engine should easily turn that 15" prop, and really don't want to drop anymore in pitch unless I can absolutely rule out engine/fuel issues.
One mechanic suggested that the engine could be starving for air, said to run with the motor box off and see if that helps. Otherwise, he felt it was probably a carb issue.
Any suggestions?
Thanks!
Engine: 5.7L Mercruiser - 250hp, 2 Barrel Mercarb, Thunderbolt 5 Ignition
SternDrive: Alpha Gen II
Last year I rebuilt my carburetor, replaced rotor, cap and plugs during a tune-up. Engine runs great at idle and throughout the rpm range with a slight vibration in engine at around 2000 rpms but is smooth outside that rpm. I am running a 15.25 x 15 prop and with 5 people on board and full gas tank I am taching 4200-4300 rpms. I know I should be around 4400-4800 and would like to prop it in that range with the load I described above for my offshore fishing trips.
Original owner of the boat had a 19" prop and I was able to get 3900-4000 rpms at WOT, so I switched to a 15" prop that I had on hand thinking that would definitely get me in the range.
I currenlty have a rich idle mixture because as I'm trolling I can smell fuel in the exhaust and after putting the boat back on the trailer I have a soot line on the transom. The idle screw is at 1.5 turns out from seat, which I thought is a pretty good starting point. I haven't tinkered with that yet.
Just wondering if my problem of not reaching WOT could be my rich idle carb mixture. I don't have a miss in the ignition that I can tell, the engine idles and accelerates great. I figured if I had a cylinder misfiriing I would be able to hear it or see my rpms flucuating a little.
Vacuum readings are good, I need to run a compression test, but that requires me to remove my exhaust manifolds due to the limited engine access (BAD Sea Pro design). I figured I would be able to see a weak cylinder or valve in the vacuum test, and I didn't.
I just feel this engine should easily turn that 15" prop, and really don't want to drop anymore in pitch unless I can absolutely rule out engine/fuel issues.
One mechanic suggested that the engine could be starving for air, said to run with the motor box off and see if that helps. Otherwise, he felt it was probably a carb issue.
Any suggestions?
Thanks!
