Exhaust manifolds, time to replace?

[flashback]

Here's what one of mine looked like after about 25 years in what I think was fresh water tho who knows with a used boat. The other side was even worse...(a replacement on the right)

 

[Scott06]

This is the line that feeds the starboard side. This side gets noticeably hotter than the port side, but I can still keep my hand on it while running. Port side is cool to the touch.

Not unusual that the two sides are different temps especially if boat sits un even

 

[Lou C]

I’ve been on the hull truth website a long time & it is a fishing/Fla/Gulf Coast group and are very much pro out board. What I see is that you can buy a new OB but don’t expect more than 10-15 years out of it. The blocks are cast alu with coated or sleeved cyls. Open deck with free standing cyls.
More prone to overheat damage and the alu can deteriorate and undermine the sealing surfaces. I’ll take a closed cooled Chevy over a 25-30k alu wonder in salt water.

 

[jakwi]

Here's what one of mine looked like after about 25 years in what I think was fresh water tho who knows with a used boat. The other side was even worse...(a replacement on the right)

Looks like you got your money out of that one!

 

[jakwi]

Not unusual that the two sides are different temps especially if boat sits un even

It's doesn't really, and today was on trailer

 

[Scott06]

It's doesn't really, and today was on trailer

That’s the point on the trailer usually side to side it will be uneven

 

[Lou C]

The water flow out of the stat housing is not 100% equal and on mine the (OMC/Volvo style) the starboard is a bit hotter both on the trailer & in the water. What’s more important is how hot they get after coming off plane

 

[flashback]

Looks like you got your money out of that one!

I got the boat a couple of years ago and spent most of last summer replacing old parts. This summer I've been able to use the boat some but I find there's always something needs fixing..

 

[jakwi]

I’ve been on the hull truth website a long time & it is a fishing/Fla/Gulf Coast group and are very much pro out board. What I see is that you can buy a new OB but don’t expect more than 10-15 years out of it. The blocks are cast alu with coated or sleeved cyls. Open deck with free standing cyls.
More prone to overheat damage and the alu can deteriorate and undermine the sealing surfaces. I’ll take a closed cooled Chevy over a 25-30k alu wonder in salt water.

I'm with you, if I have to repower again I'll definitely go closed cooling. That and dry joint and I'd only have to replace the elbows once in a while

Outboards are nice, but they definitely have a more limited life.

 

[jakwi]

Do you think the preformed hoses are worth it. It'll be more than 100 for both sides. Or I could just get coolant hose at the autoparts store

 

[flashback]

As long as you can route it with moderate bends the dayco hose is a good choice and available most anywhere...

 

[Lou C]

I just used heater hose make sure you don’t make ‘em too short so they don’t kink & restrict flow. 3/4” inside diameter IIRC.

 

[Lou C]

I'm with you, if I have to repower again I'll definitely go closed cooling. That and dry joint and I'd only have to replace the elbows once in a while

Outboards are nice, but they definitely have a more limited life.

Agreed in fact when I do repower I am going to see if I can adapt the Merc Dry joint to my OMC/Volvo Y pipe. Might work because both used elbows with a 7* down slope angle.

 

[Searay205]

First boat was 1987 3.0 liter mercruiser. Sold boat 2018 and still running today, 1000's of hours. All salt water. First manifold failed after 10 years. Back side of exhaust passage thinned over years due to exhaust gas temp boiling water on exhaust manifold. Rest of manifold was nominal thickness. Buddy had 5.7 liter were manifold cracked in corner due to sediment build up and overheating in corner. I bust manifold apart rest looked perfect, 9 years old salt water. Have new Cat 5.0 mpi, manifolds outrageously priced. FLA salt water, replaced after 10 years, bottom line waste of money, they are so thick they never fail. Your manifolds look fantastic. Risers take beating because that is where exhaust gas meet air, horrific environment. Never hear or seen an engine or head corrode through. 3.0 liter very thin behind water pump due to water pump impeller, again 30 plus years zero issues on my 1987.