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View Full Version : Cant get over 2300 rpm



drevil
07-18-2008, 02:03 PM
"Take your best shot.
351 pcm(ford), raw water cooled.standard rotation engine will not go above 2300 rpm under load. Rarely if wide open throttle it will take off suddenly(out of nowhere) but as soon as you throttle back a hair its back to 2300.
heres what Ive done so far:
new filters and water seperator
new plugs
new dist cap
new rotor
new wheels(nothing bound on the shafts)
new coil
rebuilt carb(holley 600)
swapped carbs
new risers and manifolds
swapped fuel lines with other engine after the seperator
swapped fuel lines at the pick ups on the fuel tank
new plug wires
new fuel line
nothing has made a difference.
since changing the manifolds and risers(it really needed that) engine runs warmer and pumps a less. pulled all hoses from seacock to circulating pump and they are clear. even blew out the oil cooler. pulled raw water pump tonite to check splines
why am I running hot now?
but most important, why are my rpms low?"

romans116
07-18-2008, 03:48 PM
It sounds like you have done more than I have to cure my problem. Mine will not run over 3800. I am down to the distributor and the ballast resistor. Will let you know if my problem gets cured by either of these problems. You may want to look at my post title 1987 PCM cutting out at 3800 rpm's to see the comments I have received.

mfry
07-08-2009, 09:01 PM
"there may also be a stupid little thing on top of your fuel tank right where the fuel line exits the tank and heads to the engine. It's a metal fitting that's about 2 inches long. When the engine is off or at low rpm the fitting has a ball that retracts into the housing to stop / reduce fuel flow. When you rev, it pulls the ball and spring to open up the fuel line. These things get stuck and need to be replaced. Very simple $10 exercise to see if that is the culprit. This assumes everything is working perfectly at 2300 rpm. I think your problem is fuel flow"

mfry
07-09-2009, 03:52 PM
OK. i've been reading my butt off on this issue. I have the same symptom in my post and the remedy i suggested above is a problem i also had but I don't think this is your problem. I think our boats are going into "limp" mode. I will be cruising along at ski speed and it just starts to gurgle. When i pull the throttle back to about the 2500rpm range it is fine. try to accelerate and same thing happens. shut key off and restart and it goes back to normal for a minute and then starts the gurgle thing again. There was a post way down the list that said try to change the plug wires. that's where i'm headed next. i do believe my boat is going into limp mode but i have to pull back on the throttle to the 2500 rpm position which is the limp mode rpm. so it's not automatically just going down to 2500.

shamrock20
07-10-2009, 05:44 PM
I had a problem like this too. It was due to a loose fuel clamp and letting air get sucked in to the fuel line and starve the engine. Check your fuel lines for cracks or loose fittings. These are suction lines from the tank to the fuel pump so there is no pressure on them just a vacuum

drevil
07-10-2009, 11:50 PM
Thanks. It wound up being a bad distributor. The gear off or the cam gear would climb up and the distributor wasnt advancing. New distributor and all better