SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: jamiemwedmore1234 on July 27, 2015, 01:30:52 PM
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Went to the river this weeken me and a buddy my boat ran great his boat possible some serious motor problems so shorten up the story when on a long 20 plus mile run dwn river on our way up river he decided to flat foot it almost all the way back at 4500 rpm when we parked it motor was pretty hot oil pressure went from 65 dwn to 20. We let the boat sit drove it to the launch ramp running badly Later that nite pulled the plugs water in 6 of 8 cylinders milk shake oil I think over heated the oil block seemed warm valve covers un touchable is it possible to blow both head gaskets at once. He did a compression test today and to dead cylinders motor is 100% stock 454 any insite on this would help thanks
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Welp got one head off
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Time for a new motor
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Looks like a series detonation problem.
Sorry to hear.
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So why do you suppose it had a detination problem in one cylinder would the crack in the head do it
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Looks really lean to me.
Most likely the crack is the result of the hammering of the detonation. I would also check the bearings.
The result of the detonation is the pitting on the piston which has deposited the molten aluminum (silver specs) all over the combustion chamber.
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Sounds like the motors coming out going into the shop what should I be looking for so this doesn't happen again it has center rise exhaust and 750 single pump vac sec and a msd ingnition
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Is it a single or dual plane intake? If dual, has the center divider been removed? What jets are in the carb now?
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That think detonated itself to death. I agree with Mr. Joe. Lean as hell and probably too much timing.
What carburetor is on this deal, 750 vacuum secondary what?
Ir almost looks as though the vales started coming apart.
Fat is not fast, but it's safe.
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Holley carb timing unknown he just bought the boat 2 months ago 1st trip out grenades the pump it has a edelbrock intake I'll have to find out what one and the heads are peanut port not that it matters and the carb was a vac sec carb that they made mechanical sec with a nut and bolt the other cylinder bank had signs of water in it but not near as bad
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Here's the other head
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He had some silencers in the exhaust tips that he took out and the tips had no flaps at all the tips are about 8"-10" below the center rise exhaust manifold with about 18" of hose could that have gotten water up in the cylinders
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the carb was a vac sec carb that they made mechanical sec with a nut and bolt.
That modification killed that engine IMHO.
GT
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What do the plugs look like
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That modification killed that engine IMHO.
GT
that sucks I called a carb shop asking if the carb would still wrk the same and he said if it's running good run it. I question that as soon as he bought the boat
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that sucks I called a carb shop asking if the carb would still wrk the same and he said if it's running good run it. I question that as soon as he bought the boat
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The problem I have with it is the carburetor no longer had a way to control the velocity, as the velocity drops with low vacuum, as does the ability to pull fuel.
With the carburetor in it's normal form, when the vacuum drops, as does the velocity, the secondary butterfly does not 100% open, keeping the air fuel ratio pretty Damn close.
It would have likely been fine in the short term, but the long run likely was too much and had a cumulative effect.
When we ran the marathon boats we were very diligent on the wot tune. Mainly because that's where she ran, but also because I could not afford to break anything.
GT
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If you are going to run that far and hard I recommend a step retard box and set it to at least 3-4 degrees retard. You don't need all the that timing at full speed.
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Head gasket
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