Eliminated572

These are 572 9.1:1 Carbed solid roller motors. Cannot figure out what is going on. Port side motor runs About 400 RPM lower and sluggish compared to the Starboard at any load once on plane. I need to stagger the sticks a good amount to keep RPM close and going thru much more fuel on that port motor (They feed from their own tanks) as a result. Verified tachs were right by harmonizing motors. Starboard side has the power steering just as a FYI. Has a miss aswell when trying to load that motor and definitely not as "Stout" as the starboard side. Aprox 75 hrs on motors. On the hose or low load it is fine. No miss, seems perfect. Idle speed up to the point of plane both sticks yield same RPM. Planning and once up on plane that's when I notice it from there all the way to WOT and everything in between.

Thus far have done the following: New caps, rotors, wires, plugs both motors. Cleaned reluctor wheel and looked at magnetic pickup even though I've heard that MSD thought that couldn't be it . Compression check aprox (within 2-3%) 175 all cylinders. Ran all the valves on both motors to .024. Noticed each rocker seem to do a full open/close cycle so not a cam lobe (plus idle and low load is fine). Swapped MSD boxes and coils between both and problem didn't follow. Drives just gone thru. Throttle linkage verified. Plugs all read a touch on the dark side so a bit rich but both motors about identical. Timing on both motors locked in at 32 and verified.

I'm running out of ideas and have been trying to figure this out since I bought it 2 months ago.....Anyone out there can help point in the right direction? I appreciate the help.

mike tkach

iTrader: (3)

did you change the fuel filters,what do you have for fuel pressure?

Eliminated572

I drained both filters as they were fairly new. No water or any debris. Pressure is 7psi on hose. Haven't checked under load. Pumps are edlebrock mechanical pumps with regulated returns the best I figure it. The regulator actually regulates what gets returned to the tank. Different type of system I know but other motor has no problem.

blue thunder

Did you check float level in water? Maybe you are running your secondaries low. If those are correct maybe swap carb side to side.

BBCLiberator

iTrader: (2)

Pull it now.

Eliminated572

Pull the motor and go thru it? Figured I'd run thru some more tests before it came down to that. No, didn't check levels while in water. I guess I could verify the jetting in each carb and swap them side to side...carbs are 1050 doms by the way.. Also as a recap all plugs are showing on the rich side. Both motors. If I stab the sluggish motor it doesn't fall on it's face like it's running out of fuel. Just is lazy and had some random faint spitting. This is why I thought ignition related initially. I appreciate everyone's insight. Keep it coming thanks

Mr Gadgets

Did it ever run correctly? When did it change?
Any chance the crank dampner moved on you?? Verified timing at speed? Not easy to do, I know but it might tell you something. If the distributors are locked it should be the same all the way to WOT, but I am grabbing at straws here. If something is loose in the distributor it could be retarding it??
Did you check the voltage to the MSD's, and look for good grounds. Under load if the voltage drops to them (they don't like below 10v if I remember), it could shake things up some???
Back to basics, Air, fuel, ignition, and valve timing. Something is amiss between the two. Keep at it, you will find it!!

Good luck and keep us posted.
Dick

Eliminated572

Thanks Dick. They were both ran on dyno around the 750 range previous to my purchase but had sheets. Both built with nice parts from a known builder in Oklahoma by the name of Keith scroggin. I purchased this boat 2 months ago and this port motor hasn't been right since i purchased but the boat hadnt seen water in over a year. I haven't checked timing while on plane but on the hose they both hold 32 constant. I swapped boxes but didn't check input voltage to them. Gauge shows 14 running but I think I will actually check at the box and the coil aswell to be sure. Thank you

MILD THUNDER

iTrader: (3)

Put a mech fuel psi gauge on it. Then see what you get at full load. Had a fitting on the inlet side of pump be slightly loose once. Didn't leak fuel but sucked air, loss alot of rpm at full throttle

pughdxk

The regulator actually regulates what gets returned to the tank.