96 challenger, this cant be good

[Brew Master]

So my boat officially is getting the best of me, I have now experienced a few soft 4 corner seizure, boat runs great for a few minutes but then over heats and will not turn over due the seizure. Leaves me stranded waiting for the motor to cool down before I can start it up again. Comp is 140 on both and popp off is at 30psi on both. I rebuilt the carbs with genuine mikuni kits. Looks like one of the o-rings is failing. not sure why its running so lean, highs are 1/4 out and lows are 1-1/4 out, both just a little higher than stock. here are a few pictures.

 

[Guest_User]

So my boat officially is getting the best of me, I have now experienced a few soft 4 corner seizure, boat runs great for a few minutes but then over heats and will not turn over due the seizure. Leaves me stranded waiting for the motor to cool down before I can start it up again. Comp is 140 on both and popp off is at 30psi on both. I rebuilt the carbs with genuine mikuni kits. Looks like one of the o-rings is failing. not sure why its running so lean, highs are 1/4 out and lows are 1-1/4 out, both just a little higher than stock. here are a few pictures.

did you perform a pressure test to see if any of the crank seals are leaking air?
is the overheat from lack of water or heat from running lean?
from the pics I don`t see any piston wash at all...
How are the fuel lines/filter/pump?
I have my settings at 1/4 out on the high`s and 1.5 out on the lows bc I running 40:1 premix...

 

[Brew Master]

did you perform a pressure test to see if any of the crank seals are leaking air?
is the overheat from lack of water or heat from running lean?
from the pics I don`t see any piston wash at all...
How are the fuel lines/filter/pump?
I have my settings at 1/4 out on the high`s and 1.5 out on the lows bc I running 40:1 premix...

I have not done any case pressure test, its a brand new rebuilt motor so I didn't bother, but I can if necessary. The overheating is in my opinion from lack of fuel, there is zero wash on the pistons. I went through the entire cooling system and everything checked out. The fuel and oil lines are all brand new and I rebuilt both carbs with mikuni kits. This boat is really pissing me off, so far I put a new impeller and wear ring, all new bearings and seals in the pump, new carbon seal and bellow, new fuel and oil lines, rebuilt the carbs, reupholstered the seats, what else does it want from me ?lol oh and a new scupper valve!

 

[Guest_User]

I have not done any case pressure test, its a brand new rebuilt motor so I didn't bother, but I can if necessary. The overheating is in my opinion from lack of fuel, there is zero wash on the pistons. I went through the entire cooling system and everything checked out. The fuel and oil lines are all brand new and I rebuilt both carbs with mikuni kits. This boat is really pissing me off, so far I put a new impeller and wear ring, all new bearings and seals in the pump, new carbon seal and bellow, new fuel and oil lines, rebuilt the carbs, reupholstered the seats, what else does it want from me ?lol oh and a new scupper valve!

same here, new reman engines and I didn`t pressure test bc of that.
did you change the pulse line, what about the fuel pump or fuel baffle in the tank, just a few things to check.
I hope someone here can get you squared away... Good luck...

I have a boat load of dough in ours as well x2 bc it is a twin 787...

 

[Dennis]

Can't really tell much from those pictures. Pictures of the sides of the pistons and cylinder walls, spark plugs would be great to have. :cheers:

 

[Brew Master]

Can't really tell much from those pictures. Pictures of the sides of the pistons and cylinder walls, spark plugs would be great to have. :cheers:

Hey Dennis, can really get a picture of the side of the psiton because the motor is still assembled, if you click on the thumbnail pictures it will make them bigger and you can see the detail in the pictures a lot better. Im not that concerned about the cylinder walls as the seizure was pretty soft. I can get a picture of the plugs up today. Thanks Mike

 

[Brew Master]

So do the fuel selector valves go bad at all? I know on the Polaris watercraft side they do and cause lean issues. I think I will bypass mine and see what happens. I'm going to pull the fuel baffle as well

 

[howie099]

ok your compression is low for a new rebuilt you should much closer to 150PSI on each cylinder. That one cylinder looks like you are leaking water in since I see rust forming. I would contact the rebuilder before you take it a part amymore or you might void your warranty if you have one. I looks likes you are damaging the skirt of the piston; I can see marks on the side of the cylinder walls. If you are leaking air or water I would stay it is from the head since you have rust forming there.

If it was my engnie I would send it back for another one. You more than likely have some piston skirt damage that will just get worse real quick.

 

[Brew Master]

ok your compression is low for a new rebuilt you should much closer to 150PSI on each cylinder. That one cylinder looks like you are leaking water in since I see rust forming. I would contact the rebuilder before you take it a part amymore or you might void your warranty if you have one. I looks likes you are damaging the skirt of the piston; I can see marks on the side of the cylinder walls. If you are leaking air or water I would stay it is from the head since you have rust forming there.

If it was my engnie I would send it back for another one. You more than likely have some piston skirt damage that will just get worse real quick.

Thank you for the response, the motor does not have a warranty. The previous owner payed a local powersports place to put in a new rebuilt motor, it is an SBT motor. I DO NOT blame SBT for this but I dont think the head was sealing right because you can tell by the paint on the bolts that the head had not been taken back off, I ordered a new o-ring kit from SBT and im in the process of wire wheeling the head clean, its seems to be ok but there are a few small nicks and gouges in it. I feel the bulk of my issue is a fuel and or oil delivery but im sure the leak in the oring is not helping the issue.

I bypassed my fuel selector valve last night and today I plan on pulling the fuel baffle to check it and the tank for debris. Thanks for the help. Mike

 

[Brew Master]

is there supposed to be a fuel return line restrictor? SOmething to help keep fuel pressure