Thread: Opinions on 66V meltdown
09-18-2007, 06:52 PM #1
Opinions on 66V meltdown
Guys, this is my old 99 XLT I sold to a friend, and after 2 tanks of fuel this is what happened. There was about 6" of water in the hull when I pulled the motor.
I have a new/used top end on it now and pressure tested the engine, it held 10 psi for maybe 2 minutes, then drops to 7 psi and stays there for hours. I will test fuel pressure when its running in a few days.
09-18-2007, 06:55 PM #2
09-18-2007, 07:11 PM #3
+1 Looks very lean across the board, also an additional problem w/ #1. I'm sure the water didn't help things also.
09-18-2007, 07:18 PM #4
This is really a weird one. #3 had a ton of oil in the bottom of the crankcase, 2 had some and 1 had a small amount. All 3 pistons had a light seizure on the intake side as well. I removed the oil pump and rigged it up in my bench vise, ran it with a drill and all 3 lines had the same output.
He told me when it slowed down they pulled all 3 plugs and #3 was totally oil fouled, 1 and 2 were normal. He put 3 new plugs in and said it ran much better then lost power again.
Last edited by Robsauto2; 09-18-2007 at 07:23 PM.
09-18-2007, 07:28 PM #5
What wash... there isn't any.
Whats interesting is under the black dry carbon you can see their use to be a decent wash out area. Something happened. Was the fuel octane changed? Did something lean it out?
When it’s black and dry all over like that=no good
See the eroded edge of the piston that has the most damage. That is detonation/pre-ignition
When the top edge of the piston dome to the piston sides loses its sharp edge = deto starting.
For recreational very safe use, you should have about an inch all around port area of washed off piston.
09-18-2007, 07:35 PM #6
Well there is a chance the fuel was not totally fresh, maybe 2 months old. It had 150 psi when I sold it to him and warned him to use only 91 octane. The top end I bought had a head with it and it measured 140 psi when I was done. I put the old head back on and got 150 again, so on went the new head, back to 140 psi so that should help a little.
What would it look like if it was water intrusion?
Last edited by Robsauto2; 09-18-2007 at 07:37 PM.
09-18-2007, 08:23 PM #7
Rob the number 2 piston on the ski I am rebuilding looks like that. It had a ton of oil in the crankcase too. No water. I think the heat causes the oil to lose its viscocity and it runs to the bottom.
How did the water get in there? If there is a leak he should get it fixed. Was there any water in the crank case?
The ski I am working on leaned out on number 2. She may have some old gas in it as well. I need to get some more history on it.
09-18-2007, 08:32 PM #8
Very lean,looks like the excessive heat build up is what cooked the top of the pistons.
09-18-2007, 09:24 PM #9
That 1st piston looks washed like it sucked in some water.
09-18-2007, 09:57 PM #10
I have seen this motor in person and the #1 piston had the ring spun around and started chewing it off then it stuck. I am still of the opinion that the spun ring caused the initial heat and this in turn took out the other pistons.
If you look at the piston on the left you can see the edge of the ring that should be at the alignment pin.
Last edited by OsideBill; 09-18-2007 at 10:41 PM.
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