Ever since I bought my current boat, it has had an issue with the Stbd motor RPMs. It is an 83 340 DB with originally configured 454's. The blocks have been replaced as part of it being re-outfitted several years ago.
The Port motor will idle all the way down to 400 if I wanted it too. (I tried it) No issues there. The Stbd will as well, but with exceptions.
After starting, the idle of the Stbd motor will climb to 1100 or so, and often will not go down. It is not a choke issue (I wired them open just in case). If I can get the RPMs below 1000, I will go out. While out, the RPMs will fluctuate at idle between 1100 and my real idle speed of 650. This is the funny part..... There seems to be only 3 RPM ranges it will settle in. 650, 900 and 1100. It does not constantly vary up and down. It could be fine for a few minutes to a few hours at 650, but suddenly jump to 900 or 1100.
I checked for vacuum leaks. Found none. All fuel filters have been replaced as part of general maintencance. No change....
Anyone know why my RPMs would change like this? It has the Thunderbolt 4 ignition. I have not replaced the plugs or wires yet, but do not see how they could be an issue (plugs are a nice golden brown anyway).
Thanks!
The Port motor will idle all the way down to 400 if I wanted it too. (I tried it) No issues there. The Stbd will as well, but with exceptions.
After starting, the idle of the Stbd motor will climb to 1100 or so, and often will not go down. It is not a choke issue (I wired them open just in case). If I can get the RPMs below 1000, I will go out. While out, the RPMs will fluctuate at idle between 1100 and my real idle speed of 650. This is the funny part..... There seems to be only 3 RPM ranges it will settle in. 650, 900 and 1100. It does not constantly vary up and down. It could be fine for a few minutes to a few hours at 650, but suddenly jump to 900 or 1100.
I checked for vacuum leaks. Found none. All fuel filters have been replaced as part of general maintencance. No change....
Anyone know why my RPMs would change like this? It has the Thunderbolt 4 ignition. I have not replaced the plugs or wires yet, but do not see how they could be an issue (plugs are a nice golden brown anyway).
Thanks!
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