Motor question.

[ericcarr]

Ok, I will be in the near future, like the next few weeks or so, be purchasing a good used motor for my 90 sea ray sundancer. It use to have the 90 7.4 liter 454 in her. I guess my question is what all years motor will bolt right up to it? Can I use any 454 or does it have to be certain years?

 

[alldodge]

Get the same year or newer and it will bolt up. Could even drop in a 502 if your willing to change the intake/carb

 

[ericcarr]

Couldn’t I get pretty much any 454 marine motor?

 

[achris]

Couldn’t I get pretty much any 454 marine motor?

Nope. '454' has had quite a few 'generations' and getting the wrong one may mean dealing with things like accessory mounting position differences. Or no hole for an accessory (that was on your old engine)...

This is worth a read...

The Full Story Behind Chevy's 454 Big Block V8

The Chevrolet 454 V8 originated in 1970, it evolved from the famous 427. Its improvements allowed versatile usage.

www.hotcars.com

And here... (talks about the L19, Mark IV, Generations V, VI, VII)

Chevrolet big-block engine - Wikipedia

en.wikipedia.org

Chris.......

 

[ericcarr]

Ok but if I get a generation 4 motor I should be good to go right? What years are the gen 4’s anyway? I know they were till 90 but what year did they begin?

 

[Scott Danforth]

1990 is a change year

you could have a MK4 454 which is 1978-1990. or you could have a Gen V which is 1990-1995

because the coupler is different, there are additional things you need to look at.

first you need to identify your motor

stamped steel valve covers = MK4
aluminum valve covers = Gen V

me personally, I would drop in a Gen VI 454 (1996-2000) or a gen VI 502 (1996-present) and change all the items needed changing

 

[ericcarr]

Couldn’t I drop in a motor from a car it does it have to be a mercruiser?

 

[ericcarr]

What’s the difference between the couplers… I do have that left over from the old motor, I parted out the motor…

 

[ericcarr]

1990 is a change year

you could have a MK4 454 which is 1978-1990. or you could have a Gen V which is 1990-1995

because the coupler is different, there are additional things you need to look at.

first you need to identify your motor

stamped steel valve covers = MK4
aluminum valve covers = Gen V

me personally, I would drop in a Gen VI 454 (1996-2000) or a gen VI 502 (1996-present) and change all the items needed changing

What all will need to be changed?

 

[Scott Danforth]

Couldn’t I drop in a motor from a car it does it have to be a mercruiser?

big blocks have not been in a car since the 70's

you can get a TRUCK motor, strip it down to short block and heads (pull it apart) and install marine head gaskets, brass core plugs. you will also need a marine circulating pump.

then you can bolt on the marine accessory drive, rotating electrics, etc.

you will need to source a marine intake as you are most likely carbureted and engines from the late 80's up were fuel injected.

If you are looking for a complete motor, get a complete bobtail

 

[ericcarr]

But as far as the internals, I don’t need to change anything on them?