Mercruiser 5.0 replacement

[cjstimpson]

Hi, I'm looking at replacing a 2008 Mercruiser 5.0 TKS using a long block and transferring components. How can I know if the long block I order is a fit? There's also a 5.7L which might be a fit as well, but it isn't clear to me whether any extra tuning is needed for the larger displacement, such as on the carburetor.

Any tips are appreciated!

 

[Scott06]

Hi, I'm looking at replacing a 2008 Mercruiser 5.0 TKS using a long block and transferring components. How can I know if the long block I order is a fit? There's also a 5.7L which might be a fit as well, but it isn't clear to me whether any extra tuning is needed for the larger displacement, such as on the carburetor.

Any tips are appreciated!

If it is a vortec long block 96 and newer it is identical to what you have. Good time to drop in a 5.7 which is externally identical. May have to reject the carb or step up to a 4 bbl edelBrock 1409.

I installed a partial engine from these guys in 2016 has worked excellent for over ten years now. Below is a 5.7 package with carb and intake will drop in and might have to go up in prop pitch 2” or so

5.7L Vortec Marine SILVER Package - 315 hp - (1967-2015)

5.7L Vortec marine engine-SILVER Package (1967-2013 replacement)

michiganmotorz.com

 

[nola mike]

Might want to check out this thread:

1997 5.7L thunderbolt ignition. Slow crank

Hi guys Okay I've done a lot of research on the internet and iboat, and I'm stumped still. Hoping someone could steer me in the right direction with my individual problem. Took the boat out of storage from winter, everything fired up just fine, Strong crank and fired with minimal effort. went...

forums.iboats.com

 

[Bondo]

Hi, I'm looking at replacing a 2008 Mercruiser 5.0 TKS using a long block and transferring components. How can I know if the long block I order is a fit? There's also a 5.7L which might be a fit as well, but it isn't clear to me whether any extra tuning is needed for the larger displacement, such as on the carburetor.

Any tips are appreciated!

Ayuh,...... Welcome Aboard,....... How did you come to the conclusion that you need a new/ rebuilt long block,..??..??

 

[cjstimpson]

Ayuh,...... Welcome Aboard,....... How did you come to the conclusion that you need a new/ rebuilt long block,..??..??

A mechanic diagnosed this for me and said a couple cylinders have too little compression. It overheated and I'm guessing the new impeller had problems.

 

[cjstimpson]

If it is a vortec long block 96 and newer it is identical to what you have. Good time to drop in a 5.7 which is externally identical. May have to reject the carb or step up to a 4 bbl edelBrock 1409.

I installed a partial engine from these guys in 2016 has worked excellent for over ten years now. Below is a 5.7 package with carb and intake will drop in and might have to go up in prop pitch 2” or so

5.7L Vortec Marine SILVER Package - 315 hp - (1967-2015)

5.7L Vortec marine engine-SILVER Package (1967-2013 replacement)

michiganmotorz.com

Thanks for the link. And for the tips about the carb and prop. I was looking at perhaps getting this one.

Remanufactured 5.7L Vortec (1997-up) Marine Base Engine

Family owned and operated with over 40 years in the marine engine and parts industry. Our Florida location provides you with affordable marine engines and parts

marineengines4less.com

 

[alldodge]

With the overheat and a blown head gasket, most likely all you need is a new head gasket

 

[Scott06]

With the overheat and a blown head gasket, most likely all you need is a new head gasket

I missed that 100% if it’s just a head gasket due to overheat worst case you need the head resurfaced and valve job

 

[cjstimpson]

To not leave this story open ended, I learned both head gaskets are blown and an exhaust valve was stuck open. Next, I'd like to know if the head/block is warped. Does anyone have tips on knowing how to find that out? I've done plenty of engine work before, but not on heads.

 

[Chris1956]

You could put the blue dye on the head mating surface and a piece of sandpaper on a piece of plate glass and rub the head around to see where the dye comes off. Obviously, the old head gasket needs to be scraped off first.

It is important to find out why the valve is stuck open. Is it bent?

The block would need to be done with a steel straight edge, and your eyeball.

 

[cjstimpson]

You could put the blue dye on the head mating surface and a piece of sandpaper on a piece of plate glass and rub the head around to see where the dye comes off. Obviously, the old head gasket needs to be scraped off first.

It is important to find out why the valve is stuck open. Is it bent?

The block would need to be done with a steel straight edge, and your eyeball.

Yes, the valve is bent. There's also signs it has been hit by the piston.

 

[Chris1956]

So why did the valve stick open? Valve timing jump? Overheat?

That needs to be figured out and rectified.

 

[Lou C]

I had the same problem on my old 4.3, but it ran fine for 2.5 seasons before getting a bit of water in the front 2 cyls.
I checked the block deck with a straight edge and feeler gauges as per GM specs (no more than .003" variation) after really cleaning up the block deck surfaces. I took the cyl heads to a local hot rod/machine shop and they found that both had cracks in the center cyl exhaust valve seat areas. And due to raw water cooling in salt water and erosion of the cooling passages (which could rot through and cause a hydrolock) they advised replacing the cyl heads with reman heads. So that's what I did, like 9 years ago. Turned out to be a good deal, still running well, no water in the oil, etc. Total cost was $100 for gaskets, $100 for head bolts, and $550 for cyl heads. The thing that takes the longest is cleaning especially the cyl head bolt holes. These must be clean to get accurate torque when you install the heads.

 

[Lou C]

if you look close you can see I have a stuck valve like yours, prob due to water in the cyls from blown head gasket.

 

[Lou C]

Your cylinders look OK, I'd carefully clean off the old head gaskets, clean up the block deck and measure it. If both sides are good, take the heads to a machine shop and get them checked out, might just need a valve job but might be cracked. Reman small block Chevy heads are reasonably cheap.

 

[Scott06]

To not leave this story open ended, I learned both head gaskets are blown and an exhaust valve was stuck open. Next, I'd like to know if the head/block is warped. Does anyone have tips on knowing how to find that out? I've done plenty of engine work before, but not on heads.

Look for rust on the valves that might indicate water coming in through the exhaust. You need a long machinist rule and feeler gauge to see if the block is flat. Did the engine get hot? Might also look for lean condition as it can tulip valves.

Take the heads to a machine shop as Lou mentioned or get replacements. Michigan Motorz has new 5.0 heads for $750 each.

 

[Lou C]

I got a bargain on my 4.3 V6 remans….$275 each BUT that was back in 2017!
I used compressed air, solvent, gun brushes and thread chasers to clean out the cyl head bolt holes. I also advise threading all the bolts in by hand before installing the heads to make sure they thread in all the way. And if the old bolts are rusted just replace with ARP bolts.

 

[Chris1956]

Have you checked the exhaust manifolds for water leaks into the exhaust passages? Also check the manifold to riser joint for leaks past the gasket.

 

[Scott06]

I got a bargain on my 4.3 V6 remans….$275 each BUT that was back in 2017!
I used compressed air, solvent, gun brushes and thread chasers to clean out the cyl head bolt holes. I also advise threading all the bolts in by hand before installing the heads to make sure they thread in all the way. And if the old bolts are rusted just replace with ARP bolts.

the new long block I bought in 2016 is just about x2 now.

Hard part is if there is a decent machine shop you will be waiting for them. The machinist had my block and heads for my 65 GTO for a year before they were done.

 

[Lou C]

I used a local place in Deer Park, Long Island called Machine World. Got them in a day.

machineworldny - Bing

Intelligent search from Bing makes it easier to quickly find what you’re looking for and rewards you.

www.bing.com

though their website doesn't seem to work....