How to Install a Mercruiser Dry Joint Exhaust Manifold

How to Install a Mercruiser Dry Joint Exhaust Manifold


Hoe to install a Mercruiser dry-joint exhaust
manifold. First of all, make sure you’ve cleaned off the old gaskets. Our mechanic gave us
a good hint. He cut off the heads of some bolts to create these support pins. They will
temporarily hold the exhaust manifold while you bolt it into place. Install the gasket,
followed by the exhaust manifold. Then you can start the bolts. Don’t tighten these down
just yet. We’ll do that after we replace the support pins. Once you have all four bolts
snugged down, remove the guide pins one at a time and replace them with bolts. This unit
is a Mercruiser 4.3 liter and the bolts get torqued down in three different sequences.
The first is 15 ft/lbs, then 25 ft/lbs, and last, 35 ft/lbs. Your specs may be different
so be sure to check the manufacturer’s manual. Next we’ll install the spacer. Some engines
may not use a spacer. Apply gasket sealing compound to the circular surfaces, but not
to the bigger square surface. Install the gasket, then apply gasket sealing compound
to the new spacer and install it. Make sure you start with a clean gasket surface. Apply
gasket sealing compound to the circular surfaces, and not to the bigger square surface. Water
will travel through the circular openings, while exhaust will travel through the square
opening. Apply gasket sealing compound to the other side of the spacer, and to the same
place on the riser. The next gasket we’ll use must be installed with the flange facing
up. This hole here will go underneath the fitting for the water hose. Set the riser
in place and hold it while you install the bolts. You may have to wiggle the riser to
get the holes lined up. Start these by hand to avoid cross threading. Once you have them
snugged down, they get torqued to the manufacturer’s specifications. This unit is a Mercruiser
4.3 liter, so the first in the sequence is 7 ft/lbs. You want to torque these in a criss-cross
pattern, then we’ll torque them to 45 ft/lbs. Your torque specs may be different, so consult
the manufacturer’s manual. Next we’re going to paint the bolt heads to keep them from
rusting. Once you have the riser bolted in place, you can reinstall the hose on top and
tighten it down. Make sure you also reconnect the hose on the bottom . If you removed the
blue plug, reinstall it. These are the exhaust shutters. These prevent water from back-flowing
into the engine. If you notice scorching, dry rot, or excessive wear, go ahead and replace
them. Slip the elbow into place and pull on the exhaust boot. Make sure the exhaust boot
comes up all the way to the tab. Install the hose clamps and tighten them as you go. You
can snug these clamps down with the impacter, but tighten them by hand to avoid over-tightening. This repair is the same for both sides of
the engine. Once completed, go ahead and reconnect these wires to the ignition control module,
then run the engine and check for leaks. This concludes how to install a Mercruiser dry
joint exhaust manifold. Thank you for joining us.

7 thoughts on “How to Install a Mercruiser Dry Joint Exhaust Manifold

  1. I notice you had taken the hose at bottom , does this part of the ,can I remove at bottom to drain motor???????? I need to remove a manifold and need to drain it before replacing. where is that blue screw on plug goes to???? is that for draining engine too???.

  2. What are the bolt dimensions (2 guide pins) that you made in order to slide the manifold on? (i.e. length, size and pitch)? Thanks!!

  3. if you can help out i looked a boat with a merc 5.0 temp was at 170-180, compression at 170-175, left riser luke warm right riser hot but you can keep your hand on it, engine vibrating very bad any thoughts??

  4. i know the old wet joint style of manifolds and risers should be changed every 5 years… but how often should these dry joint manifolds and risers be changed out?

  5. Thank You for information. Helps . Riser Bolts, No part numbers and 2x mercury dealers say they can not order them due to no part numbers in computer. Ya right, Any Ideas on where i can get 8x new 9 inch bolts . Thanks

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