Give me the poop on the 420hp merc.
 

I can get what seems like a deal on 420hp engine, rebuilt with a 1 or 2 year warrantee. Long block for $3200 bucks. Is it worth doing or am I better off making engines myself? How hard will it be do you think to find another?

Jon

The older 454/420?

Good motor. Bad cam.
Swap to another cam and check the gold roller rockers for bad pivot bearings or pitted tips.

Jon- I've still got my 2 from the scarab, they're in pieces ready to be rebuilt. if interested i can get some pics. but really if everythings been done right and the builder will stand behind them for 1-2 years, that's pretty cheap. I'm running a set now that have been bored out to 461's and are making about 475 hp, hopefully more after jimv is done with my heads. you might want to list whats in those long blocks, for about the same money you can put out 420 hp or 500 hp. that's a pretty big difference for your formula.

420 in a great motor Jon. If you can get them right you'll never be sorry.

Jon have you considered a couple of general motors generation 6 big block crate motors and marinize them yourself?
How old is the 420 you are looking at and is it a salt water motor?
If so that could be a problem,
How old is the power in your formula now?
There are a ton of options availble to you depending on how deep your pockets are.
Good qualified engine builders that STAND BEHIND THEIR WORK ARE FAR AND FEW BETWEEN IN NEW ENGLAND.\
Guaranteed for two years sounds great but often they say that is not the case in a marine application.
Good luck with your project.
Brian

Re: Give me the poop on the 420hp merc.
 

I just came across this thread and need some help.
My goal is to make 500hp from a 454/420hp base motor using the stock iron heads.

Any recommendations regarding cam choice, compression ratio and head work would be appreciated.

I plan on "wedges" and "bore notch" work.

Re: Give me the poop on the 420hp merc.
 

Jon, I am running rebuilt 420 long blocks in my my 357, installed Crower cams(can't remember the spec), performer rpm intakes, w/750 Holleys and they run awesome. Obviously not the most HP by todays standards but can handle higher rpms all day. Should make your 302 get up and go reliably. And you can't beat that price if built well. btw, my 357 will see upper 60's with some chop:D Good Luck!

Re: Give me the poop on the 420hp merc.
 

two 420's in a 30 ft Velocity broke the 100 barrier for V-hulls. Hey Jon, aren't you from Lynn. You an East Lynn or a West Lynn guy?

Re: Give me the poop on the 420hp merc.
 

Josh,this is a 2 1/2 year old thread that someone dragged up!!! :eek:

Re: Give me the poop on the 420hp merc.
 

I take the blame for dragging up this thread! :D