I have a 1990, 27 ft Amberjack...

[Fishtank]

I have a 1990, 27 ft Amberjack with twin 4.3L Mercruisers.  After cruising around for a couple hours, I’ll get about 2-3 gallons of water in the bilge.  I think it is coming from a leak in the exhaust manifold.  Can a manifold be removed and welded?  Is this a difficult job?

[wingless]

The intrusion of 2-3 gallons of bilge water is a fairly quick rate and should be easy enough to observe the source.

A visualization of the source should be the first step.

The existing quick rate could get even worse. That increase could happen suddenly. Do not postpone determination of the water intrusion source and problem. It is "easy" to overwhelm the bilge pump capacity.

If the exhaust manifold is leaking then discard and replace the parts. Do both sides. Replace all parts.

The disassembly of the exhaust for internal raw water passages for corrosion should be an annual inspection. Also clean the gasket surfaces and inspect for sufficient SOLID wall thickness between exhaust gas and raw water passages. Ensure the correct gaskets are on hand for assembly.

[Fishtank]

Thanks for the reply. I'll remove for inspection and since they are at least 10 years old, I'll just plan on replacing them. I'm sure they are do based on what I've been reading. Does anyone have a ball park guess how much an exhaust manifold for a 4.3L weighs?

[Littledoodie]

the approx weight of a 4.3L manifold is 32#, the riser depends on what type you have as for the weight.

[Fishtank]

Thank you. I was worried it might be closer to 100#. Around 32# or so will be much more manageable.

[wingless]

On my boat the center manifolds have decent access, for single operator replacement. A butt pain (but doable) until two end bolts are well into the head, then easy to complete.

The outboard manifolds have less access, so I suspend from above until the two end bolts have been started.