Mildly ported 260 goes flat at 3200rpm

[99hawk]

Update... I put it in the water checked the coils with a DVA meter. All were the same. When the throttle went to WOT, they would drop and then come right back up. Tried pulling full out of a can of fuel still no difference. Plugs were black. Also had oily residue coming out of the exhaust. Also tried pushing the key in to rich en up the mixture, little more bogging. Anyone have any ideas? I have attached a link of issue under load.

http://s822.photobucket.com/albums/zz150/785rmk/Allison%20XB%202003/?action=view&current=GEDC0316.mp4

also other pics that may help

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

 

[SLOmofo]

I don't know the spec for a Merc but. I take a clean container like a oil bottle and put the fuel hose in it. Turn on the pump and see how fast it fills. Sometimes there will be something in the system that will pass fuel for a while but cuts it off or lowers the flow. Water will sit in the bottom of a filter until the flow of fuel picks it up and then the water will restrict the filter.

I work on cars and have seen all sorts of things restrict fuel lines and fuel supply sumps. Bugs (Sow bugs, earwigs), Bic pen cap, foil off the tops of additive bottles, a strip of rubber from a siphon hose.
Fuel filters on boats should trap any water and not let it get past. I've also seen the filter media it's self break loose and block flow.

The wrong type spark plugs and or wires will reek havoc of electronics. Resistor plugs and resistor wires only.

I would suggest not revving an engine without a load on it. A little blip, OK.

 

[99hawk]

Thanks for the help, SLOmofo. I understand the no load reving, but here lately finding a place to put it to do testing has been tough. We have a lot of flooding. I'll try that tonight. Thanks.

 

[h2oskiier30]

Without reading back through the entire thread, have you checked your timing?

 

[99hawk]

Thanks,h2oskiier30. I haven't checked the timing with a light, but I will tonight. It had ran great for the last 45 gallons of fuel, and like a light switch it changed. Jay Smith set the timing originally, then I matched it with another new stator. The trigger is brand new, Jay also set it. Though it doesn't mean that those parts don't go bad. I appretiate the help.

 

[h2oskiier30]

One other thing...in the one video on the hose, it doesn't look like the throttle arm is moving far enough, but it's kind of hard to tell. At wot, is your butterfly open all the way?

 

[tomoad]

x2

 

[99hawk]

Checked the butterfly - okay goes fully open and wot. pulled the map hoses off and blew through them, the very bottom fitting you can't push air through or the fuel regulator which I assume is correct. I'm going to take it to a lake tomorrow morning to check the timing with a light. Checked it once, but with no load. Also pulled the flywheel off and found a seperation in the magnets on the inner hub is it supposed to be like that. Pics below. Also rechecked the wiring harness for rub spots. Recleaned the ground wires. Also checked the voltage rectifier, it is working properly. If I don't get her running in the morning I have to leave her home and go to Truman Lake without her which really is upsetting.

http://i822.photobucket.com/albums/zz150/785rmk/Allison%20XB%202003/GEDC0327.jpg

or you can check all the pics

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

 

[99hawk]

Is there a procedure to check the switch boxes? If so, does anyone have it.

 

[zatchmo]

Kind of a long shot, but be sure to check reeds too. I had some broken cages and pedals were stuck open/torn off and it ran really poorly. Had zero power to get the boat on plane.

 

[SLOmofo]

Not probably the problem, but. The pic of the inside of the flywheel. Half of it looks like powdered rust is on it. If so something isn't tight or......

Before you go, take the time to mark TDC for each cylinder on the flywheel so you can see if the timing is jumping around on one or all at the failure speed. Put the number of the cylinder next to the mark. White Out works. Sometimes on OMC's you'll get a double fire or another cylinder firing at the same time. Puts holes in pistons!
Run it in the dark and you might see spark escaping and jumping to the head or...
To me in the vid it sounds like the ignition is breaking down or timing is jumping around.
Do you have resistor plugs and wires on it? OMC's can run like crap if resistor wires and plugs arn't used.

 

[99hawk]

Sorry SLOmofo, I have it posted on Scream and fly too. I forgot to update.
So here it is. I took it back to the local boat ramp this morning, I have a flywheel that has been marked so you can check time on every cylinder. I noticed a small crack in the flywheel hub early this morning (1am). So I checked it with a timing light on cylnder 5&6 at wot the marks were jumping around quite a bit. The trigger is new. So I'm assuming the hub is bad. I also checked the DVA on the coils at 148v at idle and it would drop a little for a split second right at wot, then would come back to 153v. My guess is the flywheel hub is dicharging the switch boxes. I have a good used flywheel hub and 2 good switch boxes coming up from Jay Smith to try out. Thanks Jay for sending me some test parts.

Scott

 

[99hawk]

Update:

Jay Smith shipped me a flywheel hub and switch boxes. So I tried the easiest thing first, the switch boxes. I switched them out, and tested them. It seems to have worked, it goes right past 3200. I'm going to the lake this weekend to give it a real test, but I consider it fixed so far. I have been working with Jay Smith and Tony Brucato to get this thing running, they are both great guys and don't mind helping out. Though I do have to give a special thanks to Jay Smith. He went above and beyond by walking me through trouble shooting techniques, sending me parts to try, and hours of help. After I figured out it was the switch boxes he was more than fair on his price to sell them to me, though we ended up trading parts. By the way, the only thing I purchased from Jay was a flywheel puller (which I needed and is very high quality). His customer service is through the roof, I highly recommend him for any job. Thanks again.

Scott

 

[h2oskiier30]

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

2nd response in the entire thread. :gasp :cool :beer:

 

[99hawk]

2nd response in the entire thread. :gasp :cool :beer:

Thanks h2oskiier30. Should've listened, but at the time all six cylinders were giving me fits. Also my rear was puckering when they told me they were $225 a piece.

 

[JaySmithRacing]

Glad to help out Scott....

Wanted to see you happy with the motor even though you were the second owner since the JSRE rebuild and mods. .

When Garrett sent it to me I was a mess, I run all motors on my run stand for 1-2 hours setting all parameters before they leave but can't run up to higher RPM range ...

Again alls well that ends well...

Thanks for the positive ink ! Hope you enjoy your JSRE engine..
Jay @ JSRE