390Express
Regular Contributor
Did a ton of work to my port motor over the winter (rebuilt the upper end, and some)...
Now I can't get it to rev consistently past 1900 rpms. Runs perfect below 1,900, idles perfect, revs perfect, will rev perfectly past 1,900, but always comes back down to 1900, near instantly. 1900 seems like a hard trigger, no matter what I do.
Thought I was starving for fuel and had a kinked fuel line. I fixed that, no better. Took apart the anti-siphon valve and found it boogered up, fixed that, no better. Fuel pressure reads fine at idle, haven't had the ability to test it running, but I'm having an issue with the oil pressure gauge, and wondering if it's a limp mode scenario.
Oil pressure gauge goes down, not up, as RPMs increase. Mechanic says that's near impossible, unless the oil pump lever fell off, and I would likely see more issues if that were the case. Claims that oil pressure can and should only go up, with increased RPMs. With that I think I may have a bad sending unit. Going to temporarily install a mechanical gauge to verify 1) what my oil pressure is, and 2) whether oil pressure increases or decreases as RPMs rise.
My thought is, could my oil pressure issue be forcing the boat into limp mode right at 1,900 rpm? I ask, because 1,900 is the "magic number" every, damn time, and doesn't seem to get even moderately better with modification.
Also in consideration is to double check timing (but I don't think that even could be the issue, it's a cpu controlled ignition, and I believe it corrects itself after the initial startup, and 2) cap and rotor.
I've already replaced all fuel filters, and emptied the racor, and found nothing significant there.
To the extent that it matters, I do not get a "check engine warning light on the dash."
Now I can't get it to rev consistently past 1900 rpms. Runs perfect below 1,900, idles perfect, revs perfect, will rev perfectly past 1,900, but always comes back down to 1900, near instantly. 1900 seems like a hard trigger, no matter what I do.
Thought I was starving for fuel and had a kinked fuel line. I fixed that, no better. Took apart the anti-siphon valve and found it boogered up, fixed that, no better. Fuel pressure reads fine at idle, haven't had the ability to test it running, but I'm having an issue with the oil pressure gauge, and wondering if it's a limp mode scenario.
Oil pressure gauge goes down, not up, as RPMs increase. Mechanic says that's near impossible, unless the oil pump lever fell off, and I would likely see more issues if that were the case. Claims that oil pressure can and should only go up, with increased RPMs. With that I think I may have a bad sending unit. Going to temporarily install a mechanical gauge to verify 1) what my oil pressure is, and 2) whether oil pressure increases or decreases as RPMs rise.
My thought is, could my oil pressure issue be forcing the boat into limp mode right at 1,900 rpm? I ask, because 1,900 is the "magic number" every, damn time, and doesn't seem to get even moderately better with modification.
Also in consideration is to double check timing (but I don't think that even could be the issue, it's a cpu controlled ignition, and I believe it corrects itself after the initial startup, and 2) cap and rotor.
I've already replaced all fuel filters, and emptied the racor, and found nothing significant there.
To the extent that it matters, I do not get a "check engine warning light on the dash."
