Engine question
 

Can some one tell me in laymen's terms about the Mercruiser 420's? Is that a high performance 454? Is it the early version of the 502? I am not for sure...

Early performance motor option, 420 HP 454's. Think I still have detailed specs in a brochure at home someplace. e-mail me a reminder and I'll see if I can scan a copy.

I assume these are in your new boat in the other thread?

-Greg

your a lucky guy ....there great engines....merc 454's with all the good stuff stell crank good rods rectangular heads..they were the good motors before the 454 mag and they only make 365 hp in the carb vesion yours make 420!!!!!!

Thanks for the info
 

Makes me feel good about my purchase......

looks like they got new Holley's on the too!!!just add good exhaust and water and your ready to rock!!!!!

I think the 420s all came with cast aluminum Gil/Merc exhaust with S/S ridsers. Are you sure they're 420s?
Check the block code on the front of the engine, it should have XF or HF as the last 2 letters if it's a 420.
Gary

Thanks Gary
 

I was told the exhaust on the boat was changed to 4" exhaust,, I will not be able to view the boat until next Saturday morning...

We have a pair of 420's in our Formula. They have never been cracked and have about 750 hours on them. Bullet proof has been what I've been told. We ran a poker run a couple of years ago, 3 hours at WOT 70% of the time and near that the rest of the time. We would give them a break about ever 10 minutes and back off a bit. They didn't even break a sweat. :D

The are build 'loose' and do go through a bit of oil at WOT. Ours have the GIL performance exhaust. The valve covers should have finned ridges, the oil caps should have spring retainers and the rollers are the gold crane series. Just open up and take a look via the oil filler.

Good choice for an older motor.

Cheers,
Trevor

Thanks
 

The amount of information on this website is amazing,,,,

The manifolds could have rotted out and they were replaced with the cheaper iron center rise manifolds. Was it a salt water boat?
I'm not sure if the center rise are up to flowing 420hp on that engine. You may gain a couple mph by changing the exhaust. If you're negotiating a price, that could be a good bargaining point.
Wild Horses is right, you should be able to see the gold roller rockers. The intake should be a high rise with a 850 holley.
All but the very early models came with the thunderbolt IV ignition.
Gary

The exhaust is not cheap by any means. For two engines, risers and pipes, the going price new in Canada is about $8,000. :eek:

It will be very hard to find a pair of used ones I would imagine.
502's are 415hp I believe.

WH

The original 420 HP engines came with cast manifolds and risers from Mercruiser with a SS tail pipe which bolted to the riser... They are usually leakers with the rubber gasket between two surfaces... If you really do your homework I would think you could find new Gil systems for about $2300 each... The application you have, I would think, would be tied to a set of #2 drives (TRS) which would require the long tubes due to the transmissions... I have seen several set of these on this website in the past several months... Good luck with your purchase...

Tnx, Karl

No saltwater
 

I was told that the boat has never been in saltwater...

It has 420's and TRS drives.

Also the engines and drives are fresh..... Too bad winter is arrving,, how many days til Spring? :)

I'm pretty sure the 420's came with the cast iron exhaust manifolds with stainless steel tailpipes. The only difference between Merc's 420hp and 425hp engines is that the Merc 425's are the ones that came with the Gil aluminum exhaust manifolds---hence the 5hp difference. They are both very good engines with Crane Gold aluminum roller rocker arms, 4-bolt main blocks, Holley carbs, forged steel cranks and forged "dimple" steel rods w/ the 7/16" bolts.

LOL :TOO OLD
;)

Another picture of the motors
 

:)

Hey, we have the updated manifolds as well. The previous owner told us they had been updated, but until now I did not know that was the difference between the 420 and 425. Geeze, I just gained 10hp without doing anything. This is a good day. :D :D

I just got a digital camara for my birthday, so I will try to get some photos if the rain will hold off tonight.

Thanks again
 

All of the information has been great!

\\
Thats only like $250 US!!!!!!
lol

Were the 850 CFM Holley's the stock carb for that motor?