Couple questions about replacing freeze damaged 454 big block

[tmh]

I bought a boat with twin 1989 Mercruiser 454 straight inboards. I hot it very cheap because it needs a new engine - one woke up from winter with milky oil and two blown out freeze plugs. I haven't had a mechanic check it out yet and I bought it assuming it will need a complete new engine installed. I have a couple of questions in my hunt for a good replacement engine. I'm in no hurry so I'll be checking around for a while.

1. If I find a complete drop in engine, will I need the same generation 454? Mine is a Gen IV I think but will confirm.

2. Can I use a same vintage 454 but from an I/O application? Are they different enough that I should only consider straight inboards?

3. Any other suggestions to keep cost down? The existing engine fires right up so I assume the components are all OK and functional, but still 24 years old and some a bit rusty looking.

I will be having the mechanic's shop do the actual replacement work, but I may do the purchasing of what we put in there.

Another fun boat project!

 

[achris]

Re: Couple questions about replacing freeze damaged 454 big block

Confirm your engine casting number... Then I'd head down this road... Engine - GM, 7.4L, V8, Stand Rot, Non Tin (#GM454LAS) | Performance Product Technologies

 

[tmh]

Re: Couple questions about replacing freeze damaged 454 big block

OK, I'll check the engine number. Anyone know the answers to my other questions.

 

[Scott Danforth]

Re: Couple questions about replacing freeze damaged 454 big block

depending on the amount of hours on the second engine, I would probably pull both. the one will most likely need a block, however why not refresh both.

 

[tmh]

Re: Couple questions about replacing freeze damaged 454 big block

Thanks. However, I am looking to contain costs and the port engine runs perfectly. My questions have to do with what engines I can use to replace mine. Will a different generation complete engine match up with mounting and also with velvet drive connection?

Thx.

 

[Scott Danforth]

Re: Couple questions about replacing freeze damaged 454 big block

the bolt pattern on the flywheel housing is the same. however with the variations, I would keep the same generation and porting on the engine.

did you take your engine in to your local engine rebuilder. that will be the least expensive option.

 

[Bondo]

Re: Couple questions about replacing freeze damaged 454 big block

I bought a boat with twin 1989 Mercruiser 454 straight inboards. I hot it very cheap because it needs a new engine - one woke up from winter with milky oil and two blown out freeze plugs. I haven't had a mechanic check it out yet and I bought it assuming it will need a complete new engine installed. I have a couple of questions in my hunt for a good replacement engine. I'm in no hurry so I'll be checking around for a while.

1. If I find a complete drop in engine, will I need the same generation 454? Mine is a Gen IV I think but will confirm.

2. Can I use a same vintage 454 but from an I/O application? Are they different enough that I should only consider straight inboards?

3. Any other suggestions to keep cost down? The existing engine fires right up so I assume the components are all OK and functional, but still 24 years old and some a bit rusty looking.

I will be having the mechanic's shop do the actual replacement work, but I may do the purchasing of what we put in there.

Another fun boat project!

Ayuh,.... An I/O motor is the same motor, just dressed abit differently,...

I'm guessin' yer gonna need 2 motors, as I can't believe somebody winterized 1, 'n not the other,...

Many Frozen Cracked motors Run Great,....
A Cracked block many times has no effect on runability,...
What's the oil look like in the runnin' motor,..??

 

[Walt T]

Re: Couple questions about replacing freeze damaged 454 big block

Its possible that after you replace one you'll notice uneven throttle positions along with different behavior on the water due to the new engine putting out what it's supposed to vs the old engine tired and worn putting out substantially less.

 

[tmh]

Re: Couple questions about replacing freeze damaged 454 big block

Thanks all for the answers. Yeah, I did check the oil on the other engine and all looks fine. I changed the oil and will run it a bit then check again. As Bondo said, BOTH engines fired up and ran great upon launch. I only checked the oil closely because the plugs were popped out on the one.

So, bottom line is the I/O and inboard gen IV 454 are the same basic block, etc. with different trimmings in some cases. Thx.

I also have another thread where I asked if I could use a Gen V or VI to replace the Gen IV IF I get a complete drop in engine. Will it mount correctly and match up to the Velvet drive correctly?

Thanks again.