Water pressure through block
11-07-2025 | 11:18 AM
#1
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Water pressure through block
Raw water cooled 350 gm. Omc cobra
curious if someone has a spec for how much water pressure, is normal
I dont presently have too much or to little
but have been searching for weird water accumulation in bilge. But was not finding much
Yesterday while draining the blocks
And system for impending freezing weather
I noticed a very heavy rust stain at elbow to exhaust manifold interface...
Was musing if this could be spraying or leaking under higher rpms..3k
I orderd gaskets
But
Since these are original 1988 manifolds of fresh water use only
I may end up ordering new manifolds etc
But thought...
How much water pressure is normal
Book is absent on details...
curious if someone has a spec for how much water pressure, is normal
I dont presently have too much or to little
but have been searching for weird water accumulation in bilge. But was not finding much
Yesterday while draining the blocks
And system for impending freezing weather
I noticed a very heavy rust stain at elbow to exhaust manifold interface...
Was musing if this could be spraying or leaking under higher rpms..3k
I orderd gaskets
But
Since these are original 1988 manifolds of fresh water use only
I may end up ordering new manifolds etc
But thought...
How much water pressure is normal
Book is absent on details...
11-07-2025 | 04:18 PM
#4
Thread Starter
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Joined: Oct 2005
Posts: 221
Likes: 124
But was curious
A few things I have to change is 180 t stat to specified 160
I drained and pulled all hoses yesterday from recirculation pump, and manifolds
very light brown wayer poured out
I have a borescope coming
I am hesitant to dump tons of money on 37 year old engines
But they run great, only light smoke from cold start
Very strong ppwer
855 hrs total
Manifolds are easy fix
stock manifold and riser is 700 to 1k per side
or Eddie marine has alum high rise for 1700 a pair
Leg is in a cast
so mt time in engine bay has been really cut back
was counting on oct getting all fluid
Etc done and put some hours on her to help plan
next steps
Boat is Very very well tsken vare of rig
11-07-2025 | 08:07 PM
#5
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Joined: Aug 2019
Posts: 1,201
Likes: 411
From: BC
The elbow to exh manifold gasket leak is very common. As mentioned...the bigger issue is water leaking into the manifold exh passage into the cyl head ports.
With the raw water just exiting into the exhaust stream in 12" with relatively open ports, you won't have as much pressure at that location, even at max engine rpm.
The pressure is all added up from the complete system restrictions at the input hose, reducing pressure as it flow through.
When you pull the risers off, you'll see how healthy they are. What the mating surfaces are like etc. Make sure you put the gaskets on dry...silicone will push them out...and leak.
With the raw water just exiting into the exhaust stream in 12" with relatively open ports, you won't have as much pressure at that location, even at max engine rpm.
The pressure is all added up from the complete system restrictions at the input hose, reducing pressure as it flow through.
When you pull the risers off, you'll see how healthy they are. What the mating surfaces are like etc. Make sure you put the gaskets on dry...silicone will push them out...and leak.
11-07-2025 | 08:20 PM
#6
Thread Starter
Registered
Joined: Oct 2005
Posts: 221
Likes: 124
The elbow to exh manifold gasket leak is very common. As mentioned...the bigger issue is water leaking into the manifold exh passage into the cyl head ports.
With the raw water just exiting into the exhaust stream in 12" with relatively open ports, you won't have as much pressure at that location, even at max engine rpm.
The pressure is all added up from the complete system restrictions at the input hose, reducing pressure as it flow through.
When you pull the risers off, you'll see how healthy they are. What the mating surfaces are like etc. Make sure you put the gaskets on dry...silicone will push them out...and leak.
With the raw water just exiting into the exhaust stream in 12" with relatively open ports, you won't have as much pressure at that location, even at max engine rpm.
The pressure is all added up from the complete system restrictions at the input hose, reducing pressure as it flow through.
When you pull the risers off, you'll see how healthy they are. What the mating surfaces are like etc. Make sure you put the gaskets on dry...silicone will push them out...and leak.
Proof will be in the pudding once the riser is detached...if its eaten or close to its limit
Replace all four for sure
