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Merc. 420 eng. ?

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Old 12-15-2004, 05:17 PM
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Default Re: Merc. 420 eng. ?

So maybe they are good motors, he says they use about a qt. of oil every20-25 hour's between changes.My 500 efi's did that from the start on 40 weight then stopped when I went to 20/50. I would think that a better set of valve covers might vent better and stop the dip stick thing.
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Old 12-15-2004, 05:57 PM
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Default Re: Merc. 420 eng. ?

LOR- I think the 420's are great engines but older. Have a compression chk done, make sure the 420's don't need rbuilding too.

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Old 12-15-2004, 05:59 PM
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Default Re: Merc. 420 eng. ?

I've always heard they were great motors. Everyone I've ever talked to who runs them praises them. Got the good stuff inside and most get a lot of hours out of them with reasonable care.
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Old 12-15-2004, 06:15 PM
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Default Re: Merc. 420 eng. ?

A compression and leak-down test will tell you if these engines are internally healthy. Usually enough crankcase pressure to lift-out the dipstick is not a good thing. Did you say the oil was milky?
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Old 12-15-2004, 07:54 PM
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Default Re: Merc. 420 eng. ?

All the factory 420 motors and 400 Cyclone Motors I've seen had springs on the dipsticks as well as the oil filler caps.
An engine survey is in order whenever you have questions about the health and well-being of the motors.
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Old 12-15-2004, 10:00 PM
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Default Re: Merc. 420 eng. ?

I'll be doing all the test for sure before I would buy or let a friend buy a motor, I just never heard the spring thing before. I think if he buys them they will get a nice set of KE valve covers to help with the crank case psi. They are still in the boat so we can even drive them then pull them.

Thanks for all the help, just wanted to hear what you all knew. They should be a nice upgrade from the whipped 454 mags. Witch will be for sale if anybody need's some motors that need to be rebuilt.
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