NorEast Fishing Forum banner
1 - 5 of 5 Posts

· Registered
57 Posts
Discussion Starter · #1 ·
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 sea**** 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?

· Registered
4,553 Posts
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

Sounds to me like a throttle cable or linkage issue. Or a fuel related problem, but after looking at your list that may not be likely. Be ABSOLUTELY SURE there is NO water in the fuel. Try to use the paste gas stations use to detect water. Remove the sending unit and dip a stick with the paste on it right to the BOTTOM of the tank

· Registered
295 Posts
you already checked/changed a lot of stuff... but here's a 2 more ideas:

1. Fuel Pump? Maybe you are not getting sufficient pressure/flow for high RPM's?

2. Spark Advance? Maybe you are not getting full advance?

If you had a linkage problem, you'd be able to see it by moving the throttle back + forth, with the air cleaner/spark arrester off (and the engine off, of course).

I put a fuel pressure gauge on my boat, a cheap, simple mechanical gauge that reads 0 - 15 psi. Maybe you could try something like that, then you could run it, + see if the fuel pressure drops off when you get up to 2300 and try to push past it.

Also, not sure what kind of distributor you have, and if it has vacuum or centrifugal spark advance, but either way, it'd be pretty easy to check it out, clean everything up, check that the weights can move freely and/or the vacuum line's not cracked or something like that. You could put a timing gun on it + check the advance too.

I think either condition (lean mixture due to lack of fuel flow, or incorrect spark timing) could cause the engine to run at a higher temp than normal.

Good luck + keep us posted.

· Registered
2,180 Posts

I don't claim any special expertise but since you've done so much here are a few from left field:

Temperature range of the plugs
A while back a friend had a similar problem on an OB and it turned out to be the plugs. Since you already changed them, maybe its the temp range of the plug causing the lack of power under load

Don't know much about IB's but could the exhaust be restricted in any way? This would cause back pressure on the motor and a lack of power

Seat belts
If all else fails, install seat belts for when it kicks in...

Good luck
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.