Mildly ported 260 goes flat at 3200rpm

[99hawk]

I just bought an XB03 with a 260. Needing some advise. The engine was just rebuilt, it had 2 hours on it. Items that were replaced by the builder: Bearings, pistons, Stator and trigger, reed valves, gaskets. The builder did a very nice job on it. I have ran 1.5 tanks of fuel through it. I went fishing and took it out was running great. I came back and picked up the wife to go for a ride and it wouldn't go over 3200 to get up on plane. It acts like it is hitting a soft limiter. It starts great hits on all cylinders. I have checked compression, all were with in a +- 2-3 psi. Brucato has went throught the ecm and no issues with the PCU. Stator ohms 4.06 on both sides of the stator. Checked spark with a timing light it was good. Changed the plugs. I think it could be a stator, but I want to be sure instead of throwing parts at it.:banghead I have a service manual ordered, but it won't get here till next week. No one in the area will touch it. What should I do?

 

[suicidealli]

i would bet it is the fuel pump if it fall on its face......

roy

 

[h2oskiier30]

Could be a switchbox, and don't rule out the high side of the stator, either.

 

[99hawk]

Thanks suicidealli and h2oskiier30. This has been very helpful

suicidealli- Do you know what the fuel pressure should be?

h2oskiier30- How do you check the switch box?

Also had a mercury guy tell me it could be a TPS? Does anyone have any specs on this engine? I found the sn to og959741, if this helps.

 

[patches]

Fuel pressure depends on what curve is in the PCU. Could be 39 or 56

 

[99hawk]

It has a black fuel pressure regulator, if that helps. I know that Tony asked that when he reflashed the computer to the engine.

 

[99hawk]

here are a few pics of the engine for references.

http://s822.photobucket.com/albums/zz150/785rmk/Allison%20XB%202003/

 

[tomoad]

black is a 56lb

 

[suicidealli]

correct black is 56.
when the fuel pumps go bad they will loose fuel pressure when you throttle up, or the just lock up. switch box usually just dies. that means your running on 3 cylinders. the high side of the stator could be the trouble.
get a fuel pressure gauge, and when you hit the throttle it will fall off if it is the fuel pump.

roy

 

[99hawk]

Thanks, guys. I'll check the fuel pressure (Fuel pressure gauge in the boat is off). For some reason the gauges are off in the boat, probably a ground wire. If it isn't fuel pressure, I'll try a stator.

 

[Dave Hensley]

Stator. Just about guarantee.

 

[99hawk]

Here is an a update. I checked the fuel pressure it is right at 56 psi and consistant when it was reved up it didn't fall off. I also checked the spark. The spark tester said it was comparable to 20k Volts, all cylinders jumped the spark 1/2" gap. I'm leaning toward the stator even though it was just replaced. I also attached a short video of what it is doing.


http://s822.photobucket.com/albums/zz150/785rmk/Allison%20XB%202003/?action=view&current=VID00013.mp4

 

[rmills280]

make sure map sensor tube and nipple is clean

 

[99hawk]

Thanks for the tip, rmills280.

 

[99hawk]

I ordered a stator. I hope that is it.

 

[99hawk]

Would a bad connection in the harness where the Allison and Mercury harness come together cause this issue?

 

[whipper]

Stator. Just about guarantee.

x2 sounds the same as when my stator went. Only other thing after I put a used stator on 4 years ago and thought it was my stator again was the pulse pump spring wore out feeding the VST tank but you dont have one of those.

 

[99hawk]

It's not the stator. Just put another new one in and still acts the same :cuss. Fuel pressure is good. It will jump a spark 1/2 an inch on all cylinders. PCU has been check out by Brucato. :banghead What else could it be? Switchbox, sensor, etc.

 

[SLOmofo]

Fuel pressure is good, but what about volume?

 

[99hawk]

Fuel pressure is good, but what about volume?

SLOmofo, how do you check the volume?