5.7 swap out question

[wellyboy]

Good morning all, I have a 1989 5.7 mercruiser that needs to be replaced. What year 5.7 mercruisers would fit in its place ,it has the center bolt valve cover pattern. and what is it that makes the difference. last but notleast I read where someone mentioned a Bobtail motor ,what does that mean ?? thanks

 

[Bondo]

Re: 5.7 swap out question

Good morning all, I have a 1989 5.7 mercruiser that needs to be replaced. What year 5.7 mercruisers would fit in its place ,it has the center bolt valve cover pattern. and what is it that makes the difference. last but notleast I read where someone mentioned a Bobtail motor ,what does that mean ?? thanks

Ayuh,.... A Short block is the Block, 'n No heads,....

A Long Block is everything Chevy, with None of the Mercruiser parts,...
In yer case, a '87 to '96 Long block would work, as yer Mercruiser pieces will directly swap,...
Newer than '96, you'd need a different intake to match the Vortec heads,...

A Bobtail motor, is a Complete plug, 'n play motor, All the Chevy parts, 'n All the Mercruiser parts, a Complete motor,...

 

[achris]

Re: 5.7 swap out question

A bobtail engine is a complete engine, pulley to flywheel. Basically, bolt on your old coupler and flywheel housing, drop it in and go.

The 5.7 Mercruiser is a standard Chevy 350 truck engine, with brass core plugs. If the rest of the engine is ok, then I'd be looking at finding an old truck engine and 'marinising' it (strip all the fruit and veg off the old Mercruiser block and put it on the truck block.... Look for an engine of roughly the same year or later. If you get a vortec, then you'll also need a new intake manifold.

Chris.....

 

[thumpar]

Re: 5.7 swap out question

What is the reason you are changing out your engine?

 

[wellyboy]

Re: 5.7 swap out question

well that clears up a lot of my questions. the reason for the swap is my current engine is locked up and I cant turn it at all via starter or.. by removing the starter, plugs and usinga strap wrench to turn it, so I just figured if I was able to find a decent motor with good compression I would be in good shape.

 

[thumpar]

Re: 5.7 swap out question

You removed the drive to make sure didn't you?

 

[Bondo]

Re: 5.7 swap out question

well that clears up a lot of my questions. the reason for the swap is my current engine is locked up and I cant turn it at all via starter or.. by removing the starter, plugs and usinga strap wrench to turn it, so I just figured if I was able to find a decent motor with good compression I would be in good shape.

Ayuh,.... Like thumpar says,... Pull the drive 1st,...

It's solidly splined to the crankshaft,...

How 'bout some more of yer backstory,..??

 

[wellyboy]

Re: 5.7 swap out question

Their is not much history here as I got the boat in this condition. now as far as the drive is concerned are you saying that a frozen drive could be causing this problem ? I was always under the assumption that a drive in neutral was completely disengaged from the engine, but now as I think about it I see where this is very possible. I would imagine if the drive is the problem then I can expect it to be difficult to remove. correct me if i'm wrong

 

[achris]

Re: 5.7 swap out question

Their is not much history here as I got the boat in this condition. now as far as the drive is concerned are you saying that a frozen drive could be causing this problem ?

Quite possibly.

I was always under the assumption that a drive in neutral was completely disengaged from the engine, but now as I think about it I see where this is very possible.

No, only the propeller shaft is disengaged. Everything else turns with the engine, regardless of which gear is selected, or if it's in neutral.

I would imagine if the drive is the problem then I can expect it to be difficult to remove. correct me if i'm wrong

Ummm, correcting you... Even if the drive is locked solid, the yoke should slide straight out of the engine coupler.

Chris.....

 

[thumpar]

Re: 5.7 swap out question

The shifting is done in the bottom of the drive. It is very easy to remove the drive. Put it in forward, take the trim pin out of the rams on the drive and the 6 nuts off the drive that hold it onto the bellhousing. It should slide off but be ready for the 75lbs.

 

[wellyboy]

Re: 5.7 swap out question

ok guys I will be pulling the drive this week at some point and I 'll let ya know what happens

 

[wellyboy]

Re: 5.7 swap out question

I took thumpar's advice and pulled the drive. I first started by draining the drive fluid, I found a very small amount of clear water first came out then about a Dixie cup full of oil(which is a very low amount if memory serves) funny thing is the oil that did come out was not even discolored as I would have thought it would be. ok now I pull the drive ,the bolts losened rite up and the drive just about fell off. now I have pulled many drives over the years and had to use at least a rubber hammer on most . after sliding the drive out a quart or so of water followed so I guess this has something to do with my problem or atleast I am hoping. it got late and dark do I could not hop up on the boat to try and turn the flywheel ,I will try that later after work. So what are you guys thinking here , Thanks

 

[Bondo]

Re: 5.7 swap out question

I took thumpar's advice and pulled the drive. I first started by draining the drive fluid, I found a very small amount of clear water first came out then about a Dixie cup full of oil(which is a very low amount if memory serves) funny thing is the oil that did come out was not even discolored as I would have thought it would be. ok now I pull the drive ,the bolts losened rite up and the drive just about fell off. now I have pulled many drives over the years and had to use at least a rubber hammer on most . after sliding the drive out a quart or so of water followed so I guess this has something to do with my problem or atleast I am hoping. it got late and dark do I could not hop up on the boat to try and turn the flywheel ,I will try that later after work. So what are you guys thinking here , Thanks

Ayuh,... The water in the bottom of the drive, 'n the water in the bellows are certainly Problems,...
'n the lack of oil in the drive is a bigger red flag,....

Does the drive turn, Manually,..?? forward, reverse, neutral,..??

Sounds like ya might need a new drive to go with yer new motor,...

 

[thumpar]

Re: 5.7 swap out question

Bad bellows and bad seals in the drive. Just try bumping the starter to see if it will turn over now.

 

[wellyboy]

Re: 5.7 swap out question

thumper I did origanaly pill the starter so I will have to put it back or use a breaker bar to turn it. whats your opinion on the breaker bar idea

 

[thumpar]

Re: 5.7 swap out question

Just use the breaker bar if the starter is not installed. All you need to find out is if the drive was preventing the engine from turning over.

 

[wellyboy]

Re: 5.7 swap out question

ok, i used the breaker bar and with very little effort the engine spun. and now with help i was able to spin the drive in forward. i am wondering if when i picked up the boat their was water in the bellows and it froze and froze everything connected to it.

 

[thumpar]

Re: 5.7 swap out question

Reinstall the starter and put a hose in the water port on the bellhousing and try to start the engine.

 

[wellyboy]

Re: 5.7 swap out question

thats the plan thumpar, i will have to try it over the weekend. i will let ya know.thanks so much for your help.

 

[acdc96]

Re: 5.7 swap out question

Put some liquid wrench or any lubricating oil (even fogging oil) in the cylinders before starting the motor. Assuming that the motor has sat a while. You want to have some lubrication in the pistons.
I did that when I first started my motor after sitting for 5 years.

DONT USE WD-40