BoatingTimbo
Petty Officer 3rd Class
- Joined
- May 18, 2009
- Messages
- 78
It's an '89 OMC Cobra 4.3L with Rochester double carb.
It now only revs to 2,000 RPM for about 30 seconds then die's out. I can pull the throttle back quickly and it will catch up with itself continuing to run leading me and all mechanics that have looked at it feeling it's definitely fuel starvation. If i drop the hammer to full throttle it will run up to about 3,500 RPM and die out after only 5-8 seconds.
I had the shop at the marina look at it a few weeks back and they did:
- fuel flow tests (pressure, volume etc.)
- Re-built the carb (after that rebuild i could run at about 3,000 RPM for hours and have no problem, if i pushed the throttle any higher it would stall out as described above)
- replaced fuel filter
- replaced fuel lines
- ran with larger/different fuel pump (no difference, although it wasn't for this exact engine). Not sure if this eng. is meant to have electronic or mechanical fuel pump (there's mounts for the mechanical fuel pump but it's running electrical right now)??
- ran on external fuel tank to bi-pass lines
- They then recommended it needed a new carb but were very unsure!
Rather then spend the money on new carb i had another mechanic look at it and he did:
- another carb rebuild as he said they used the wrong rebuild kit and was sure that was the problem!
- replace anti-siphon valve
- re-tested everything
When i ran last night it's worse after the second carb rebuild! As described above it won't go over 2,000RPM (which is barely planing) where as before it at least ran up to 3,000 RPM and won't die out after 30 seconds like it is now!!
I'm starting to think this boat purchase was a bad idea!! It's such a stress and i know boating shouldn't be!!
Do i now need to spend $600 on a new carb and $200 on new fuel pump -- to test (and find out it something else)??!??
Please help anyone... Thanks so much.
It now only revs to 2,000 RPM for about 30 seconds then die's out. I can pull the throttle back quickly and it will catch up with itself continuing to run leading me and all mechanics that have looked at it feeling it's definitely fuel starvation. If i drop the hammer to full throttle it will run up to about 3,500 RPM and die out after only 5-8 seconds.
I had the shop at the marina look at it a few weeks back and they did:
- fuel flow tests (pressure, volume etc.)
- Re-built the carb (after that rebuild i could run at about 3,000 RPM for hours and have no problem, if i pushed the throttle any higher it would stall out as described above)
- replaced fuel filter
- replaced fuel lines
- ran with larger/different fuel pump (no difference, although it wasn't for this exact engine). Not sure if this eng. is meant to have electronic or mechanical fuel pump (there's mounts for the mechanical fuel pump but it's running electrical right now)??
- ran on external fuel tank to bi-pass lines
- They then recommended it needed a new carb but were very unsure!
Rather then spend the money on new carb i had another mechanic look at it and he did:
- another carb rebuild as he said they used the wrong rebuild kit and was sure that was the problem!
- replace anti-siphon valve
- re-tested everything
When i ran last night it's worse after the second carb rebuild! As described above it won't go over 2,000RPM (which is barely planing) where as before it at least ran up to 3,000 RPM and won't die out after 30 seconds like it is now!!
I'm starting to think this boat purchase was a bad idea!! It's such a stress and i know boating shouldn't be!!
Do i now need to spend $600 on a new carb and $200 on new fuel pump -- to test (and find out it something else)??!??
Please help anyone... Thanks so much.
