mercruiser manifolds - lifetime

[gingie]

retro fit

You could retro fit but the down angle degree off the dry style exhaust is a slightly different one to the older style. Also the newer ones are a different height which would result in also changing the aluminium 90 degree bends.

In my experience i have not changed any of this style manifold or riser yet since they were introduced. Not to say they wont fail but i have noticed they are lasting longer than the old style.

Im now working on the latest generation V8/V6 units with Catalytic convertors. Which has a completely different style system. Touch wood no issues yet. 3 anodes in one exhaust alone to help protect the core.

 

[tinkicker0]

Having been on the US boating sites as a newbie boater a few years ago, they had me paranoid in thinking the damn boat was going to dissolve as soon as it hit the water.

I know my manifolds were changed by the previous owner 6 months before I bought it and I use mine in fresh water, so should be good for another 3 or 4 years going by the time expired route.

Question: My manifolds have removable steel end caps, if I were to make up a small doubler plate, tack weld it inside the end plate, drill and tap the whole caboodle to accept a suitable pencil anode.
If I ensure that I have good electrical contact twixt end plate, manifold, riser and block, would this protect the entire system from corrosion?

The engine is directly connected to a 4 inch magnesium donut anode on the transom.

 

[AndieMac]

A local techy told me a kit is available for around GBP300.00 to adapt the newer dry joint manifold system to the older centre riser system.
His opinion was to still keep checking the corrosion situation, especially for permanently moored boats in sea water.

 

[spannerman]

Interesting. My 496 is also fresh water cooled, but I don't see why this could lead to a higher pressure on the raw water which circulates in the manifolds. Could you elaborate? Ta!

There are two ways Mercruiser do fresh water cooling,

1, only the block is freshwater cooled and the raw water after leaving the heat exchanger enters the bottom of the manifold and cools that before going into the riser and out of the exhaust, which is what you have by the sound of it.

2, the block and manifold are both freshwater cooled and there is a blocking gasket between the manifold and riser to keep the freshwater and raw water separate, the raw water just cools the riser on its way out. This means that the pressure in the manifold is higher same as the block because of the pressure cap on the heat exchanger, same as a radiator cap on a car. This is the system I have, and I have had one the blue plastic drain plugs crack and blow out once the system built up pressure so I carry a couple of spares onboard.

 

[adey]

Question: My manifolds have removable steel end caps, if I were to make up a small doubler plate, tack weld it inside the end plate, drill and tap the whole caboodle to accept a suitable pencil anode.
If I ensure that I have good electrical contact twixt end plate, manifold, riser and block, would this protect the entire system from corrosion?

This company makes them for their aluminium/ceramic manifolds but I don't really see the point for cast ones. I changed my 10 year old Mercruiser manifolds/risers earlier this year due to their age and to be honest they still looked okay despite having been in salt water 51 weeks a year.

 

[julians]

Hi all.

Thought id check back in withthis thread and see if anyone had any updated experience with the dry joint exhausts.

The ones on mine are still ok after 7 seasons in salt,showing no signs of overheat, or other problems (touch wood)

Has anyone seen them fail yet (apart from due to freezing)?

Still trying to gather experiences on these, as the yanks still think that boats disolve when placed in salt water

 

[spannerman]

Interesting. My 496 is also fresh water cooled, but I don't see why this could lead to a higher pressure on the raw water which circulates in the manifolds. Could you elaborate? Ta!

My manifolds are freshwater cooled so under pressure, I have a solid gasket between the manifold and riser so only the riser is rawwater cooled.

 

[MapisM]

There are two ways Mercruiser do fresh water cooling...

Aha, I understand. Yep, of course water pressure in the closed circuit is affected.
On my boat the whole exhaust was raw water cooled.
Actually, she had the CMI s/steel exhaust, but IIRC also the stock manifold of 496 blocks was raw water cooled.