Mercruiser 4.3 Vortec running hot on one side

[Superjetjim]

Got a strange problem with differing water flow and temp between left and right hand side of engine.

Motor has been stored for a long time, drained antifreeze. Lots of crap brown water came out of blue block drains. Now running clear and reinstalled them. After a min or so of running the right hand exhaust water flow drops. If you drain the block (via the blue plugs) and try again you get decent flow for another min then it slows. Guessing I’ve got build up / debris in the motor - can this be back flushed to remove? Any tips / suggestions like running hose through drain bung hole perhaps?

Observations:
New manifolds
New risers
Water intake is from hose directly to water input.
90’ Elbows are clear / clean on riser input.
Brand new thermostat fitted yesterday
Left riser is cold
Right riser is hot to touch
No water in engine oil (have also checked under rocker covers for moisture and nothing)

Couple of videos attached so you can see the flow difference. See how the flow drops off?

 

[Scott06]

temp diff between manifolds is not uncommon, they should be hot to touch, but not so hot you cant put your hand on them for a second 180 or so.

if one manifold is higher than other will create more flow one way or other.
does your system feed the elbow as well as the manifold ? If so thee are check balls in T on thermostat housing would check they are moving ok but don’t think you have any thing to worry about

 

[Superjetjim]

temp diff between manifolds is not uncommon, they should be hot to touch, but not so hot you cant put your hand on them for a second 180 or so.

if one manifold is higher than other will create more flow one way or other.
does your system feed the elbow as well as the manifold ? If so thee are check balls in T on thermostat housing would check they are moving ok but don’t think you have any thing to worry about

Here’s a picture of my water routing. Are there balls inside this housing?

One side has steam / water mix from exhaust - other is just water.

 

[Bondo]

Ayuh,..... Is the motor sittin' Dead Level,..??

 

[Superjetjim]

Ayuh,..... Is the motor sittin' Dead Level,..??

Hi, looking at a picture from yesterday it’s leaning a little to the left due to the angle of the land I’m working off, but only a tiny amount - do you think the water is flowing towards the left hand side of the motor due to gravity hence why more coming out on that side? Is the cooling system really that rudimentary with no balanced 50/50 flow split?
Thanks

 

[Scott06]

Here’s a picture of my water routing. Are there balls inside this housing?

One side has steam / water mix from exhaust - other is just water

no balls in that housing you have cold manifold design.

again i think what you have looks fine there will be some steam as exhaust is hot. If it makes u feel more confident take a thermometer and measure temp of manifolds

 

[Lou C]

One last thing I’d check the passages in the thermostat housing; in a raw water cooled cast iron motor (especially if you run in salt water) those passages can neck down from corrosion. I have 2 OMC/Volvo thermostat housings that I alternate use of and just use a coat hanger wire to rod them out before installing with a new thermostat. Also, how old are your manifolds & elbows? You could have some clogging in the water passages on that side due to corrosion. The true test is when the boat in in the water running off the impeller in the lower unit.
These systems work on pressure balance & water will take the path of least resistance. That said one side will always be slightly hotter than the other. On mine (OMC with late model Volvo style exhaust) the starboard side runs slightly higher than the port, the difference is less in the water though.

 

[Superjetjim]

One last thing I’d check the passages in the thermostat housing; in a raw water cooled cast iron motor (especially if you run in salt water) those passages can neck down from corrosion. I have 2 OMC/Volvo thermostat housings that I alternate use of and just use a coat hanger wire to rod them out before installing with a new thermostat. Also, how old are your manifolds & elbows? You could have some clogging in the water passages on that side due to corrosion. The true test is when the boat in in the water running off the impeller in the lower unit.
These systems work on pressure balance & water will take the path of least resistance. That said one side will always be slightly hotter than the other. On mine (OMC with late model Volvo style exhaust) the starboard side runs slightly higher than the port, the difference is less in the water though.

Thanks Lou,
Manifolds and rises are brand-new.
When you say check obstructions, I assume you mean in here?

 

[Lou C]

Yes check the passages in the thermostat housing that the hoses feeding the manifolds connect to.
You make also need a better water supply hose; I use a 3/4” or 19mm when running mine on the hose.

 

[tank1949]

and if it is an old saltwater used boat, the block's passage may be corroded and plugged up. If motor was saltwater cooled for 8 years or more, I'd pitch and invest in a new block while gas prices are out of this world. Few of us can afford boating anymore.

 

[Superjetjim]

Hi lads, just a quick update on this thread for the benefit of anyone in the future.

I mounted the motor onto a bench so it’s completely level (checked it with a spirit level)

Bondo was indeed correct, now the motor is sat level equal amounts of water coming out of both sides! Also both risers are now nice and cool.

No need to do a head gasket after all
View attachment IMG_4707.MOV

All spruced and ready to go back in
View attachment IMG_4707.MOV

 

[Scott Danforth]

Bondo was indeed correct, now the motor is sat level equal amounts of water coming out of both sides! Also both risers are now nice and cool.

No need to do a head gasket after all

hard to argue ancient greek principles of a water level or Aλφαδολάστιχο

 

[Superjetjim]

hard to argue ancient greek principles of a water level or Aλφαδολάστιχο

You can move water uphill with a fork if you’re fast enough….

 

[Bondo]

You can move water uphill with a fork if you’re fast enough….

Ayuh,..... but it always Flows back down,.......

 

[Lou C]

Looks and sounds great.