1988 Merc 420's
10-15-2014 | 08:05 PM
#11
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For SOME reason...I thought these were 496 in motors?? As the SELLER "Advertised"??!! wont drag him through the mud yet! My "Thinking" was if I had a "good" bottom end....put some $$ in the Top.....600 to 625?? If I start from "scratch"...I can get there EASY....but this is just one of my "toys"....don't want to get crazier than I am.....lol Already bought Konrad Drives to replace the TRS's.....want PERFORMANCE with RELIABILITY!!
10-15-2014 | 08:19 PM
#12
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From: Moultonborough NH
What is reusable in these motors for a little more power.Also is the components quality enough that you could reuse almost all of the motor on just a stock rebuild even the camshaft if it checked out.
Reason i am thinking is seeing all these older 420s up for sale has me thinking to sell my SBC CMI and tail pipes for 1500 and maybe get another thousand out of my fresh nothing to special 300 horse 355 and buy a 420 to put in my little 19 footer..
Dumping another grand into sbc heads to get 30 horse doesn't add up to me when i could buy a 420 for 3000 and do a simple rebuild for a grand if the motor is in decent shape to begin with and have a base if i wanted to build 500 horse later if I wanted
Reason i am thinking is seeing all these older 420s up for sale has me thinking to sell my SBC CMI and tail pipes for 1500 and maybe get another thousand out of my fresh nothing to special 300 horse 355 and buy a 420 to put in my little 19 footer..
Dumping another grand into sbc heads to get 30 horse doesn't add up to me when i could buy a 420 for 3000 and do a simple rebuild for a grand if the motor is in decent shape to begin with and have a base if i wanted to build 500 horse later if I wanted
10-15-2014 | 08:42 PM
#14
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From: naples,florida
Tommy, the crank, rods, and pistons are all good quality parts. Essentially the same quality parts as used in the 500 HP carbed motor. I tore my starboard motor down at 680 hours and the only real problem found was a cracked head. Bores looked good but I didn't measure for taper or concentircity as I was boring it anyhow. The pistons looked perfect, the cam and lifters still looked excellent, it could have been very easily refreshed inexpensively. As a matter of fact, I could have just redone the heads and put it back in service with no worries.
Just what I was looking for.
I used to run the old 330 in our parsail boats and we would get 4000 hours out of them with no problems if we kept the exhaust replaced After 4 years we would replace them just for the fact that they were saltwater motors and were on borrowed time. But they ran great after being removed, never tore one down as we scrapped them soon as they came out of the bilge.. Figured if these 420 aren't too much wilder than a 330 but with much better parts and had not been ran super hard that they should be a decent motor even after 100s of hours
Good to see that they don't need the heads refreshed at 400 hours like the hp500s
Last edited by tommymonza; 10-15-2014 at 08:45 PM.
10-15-2014 | 08:46 PM
#15
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From: Moultonborough NH
Oh yeah, forgot to mention the 420's were 4 bolt blocks. It is also the perfect compression ratio for a little boost. As a matter of fact, that is essentially what the Hawk 525's were, 420's with 174 blowers on them.
