Port manifold hotter than starboard.

[Silverbullet555]

Before you say it, I know they say it's normal. But, it wasn't always this way which means something has changed. I'm going to continue working on it until its solved.

2002 VP 8.1Gi. 455 hours. Factory original except for a heater that was installed by a shop for the previous owner.

Symptoms started 2 years ago. Last year I spent most of the summer in the hospital so I couldn't work on it. At the end of the 2016 season I noticed a hot smell in the engine compartment. That started the search.

The engine temp always reads in the 165 range so the engine is not overheating. In discussion with a local shoo, I was told it is a water flow issue and not an engine issue. It happens on muffs, in the lake, level or slanted. I have put clear hoses in the water hoses to see flow and it appears that is the issue. I can see the flow to the port side is slower than the flow to the starboard side. If I pinch off the port side hose, I can force more water into the starboard side.

I replaced the raw water pump to no avail. I back-flushed the oil cooler and got 1 piece of rubber out. I have pulled the elbows to check manifolds for corrosion and they look good. I flushed the port manifold and it flushed fine. This engine doesn't have flapper, but I scoped the exhaust to check for obstructions anyway. I also replaced the thermostat. I checked all the ports on the thermostat housing and they are looking good. All the injectors were rebuilt and the o-rings were replaced.

I'm wondering if the hose from the thermostat housing to the port manifold has a collapsed section causing it to be restricted. The other potential issue is a head gasket leak letting pressure into the exhaust and slowing water down or simply adding air which reduces the cooling ability of the system.

Any ideas?

[cmattj]

Yes I've heard that as well as the design for water dispersement favors one outlet as operated to the other..

Also I've noticed with captains call exhaust as one side steams more than the other. On all my boats with it have done that (lower exhaust water flow exiting)

If you haven't already, swap the hoses off the thermostat to test the theory of dispersement and or restriction. And you'll quickly know.

I assume you’re getting temp readings from a heat gun (infrared surface) so what's the split?

I know on My Volvo (closed cooling) it would respond like a car if the head gasket failed.

Freshwater cooling would hide that issue a bit more until you picked up a miss from water in the cylinder. Or intermix in the oil.

Can't do a hydrocarbon test on fresh water cooled so.... let's start by swapping things side to side.

[Big Block Power]

I'm with Matt on this. Check the power steering cooler. How much hotter is it. I can check mine next time out too.

[Silverbullet555]

It's a 25 degree difference so not huge. I don't like the smell or the fact that it has changed. Good call on swapping the hoses on each side. Wish I would have thought about it before today.

I am using a heat gun to determine temps. I would post a video of the waterflow but don't have anywhere to host it. Wouldn't matter much either way.

I'll work on getting some hose so I can swap them and see what happens.

[Big Block Power]

I use my utube account for vids.

[Silverbullet555]

I use my utube account for vids.

Don't have one.

[Silverbullet555]

Yes I've heard that as well as the design for water dispersement favors one outlet as operated to the other..

Also I've noticed with captains call exhaust as one side steams more than the other. On all my boats with it have done that (lower exhaust water flow exiting)

If you haven't already, swap the hoses off the thermostat to test the theory of dispersement and or restriction. And you'll quickly know.

I assume you’re getting temp readings from a heat gun (infrared surface) so what's the split?

I know on My Volvo (closed cooling) it would respond like a car if the head gasket failed.

Freshwater cooling would hide that issue a bit more until you picked up a miss from water in the cylinder. Or intermix in the oil.

Can't do a hydrocarbon test on fresh water cooled so.... let's start by swapping things side to side.

Swapped hoses and flow/heat switched sides. In my mind, this would eliminate everything from the the manifolds through the exhaust. I still need to flush the ps cooler to make sure it's not restricting flow. After that, all I can think of is hoses, the thermostat housing and something in the intake in the drive blocking it.

Making progress, but summer is here.

[cmattj]

Good to hear. That plan worked out.

You'd be surprised that once your rolling how cool the manifolds get.
Stay with the plan as BB and us with making sure there are no other restrictions. Idle is the lowest volumn so ince everything is flushed and clear you'll be set.

[Silverbullet555]

Bypassed the ps cooler today and the entire drive by pulling water from a bucket via a clear hose attached to the raw water pump. No change. This should eliminate any potential for a block or restriction in the drive or ps cooler, correct?

I replaced the thermostat housing just to make sure there wasn't something going on there. No change. Replaced the raw water pump with no improvement. Swapped hoses on the thermo housing and the flow issue changed meaning that the manifolds and risers are not the issue.

It seems to be a hydro dynamic issue where the water splits to go to the circulating pump and between the two manifolds. Replacing the thermo housing should've corrected if there were issues with corrosion or erosion. But alas, nothing has worked.

Ready to put a gate valve in the side with better flow to force more water to the warm side. I think it's a hack way to fix it, but I don't know what else to check and neither do local mechanics. I do have a new thermostat to put in as a last resort, but I don't expect it to fix the issue.

[Big Block Power]

Bypassed the ps cooler today and the entire drive by pulling water from a bucket via a clear hose attached to the raw water pump. No change. This should eliminate any potential for a block or restriction in the drive or ps cooler, correct?

I replaced the thermostat housing just to make sure there wasn't something going on there. No change. Replaced the raw water pump with no improvement. Swapped hoses on the thermo housing and the flow issue changed meaning that the manifolds and risers are not the issue.

It seems to be a hydro dynamic issue where the water splits to go to the circulating pump and between the two manifolds. Replacing the thermo housing should've corrected if there were issues with corrosion or erosion. But alas, nothing has worked.

Ready to put a gate valve in the side with better flow to force more water to the warm side. I think it's a hack way to fix it, but I don't know what else to check and neither do local mechanics. I do have a new thermostat to put in as a last resort, but I don't expect it to fix the issue.

Try running without a tstat and see if she runs cooler.

[cmattj]

By swapping hose outlets you determined flow or volume to each manifold. It changed the temp as a result.
As BB said removing the thermostat will increase flow and bring temps down to at least maximize flow .

You will see the temps drop but it will risk not maintaining good running temps. The reason mfg say that a variance in temp is due to natural flow at low speeds filling a line that has no pressure pushing back.

Everything changes once your underway and the system pressure goes from 1-2 psi at idle ( yep that's all they do) up to 25 psi at 3000 rpm.

The captains call system always steam at idle one side more that the other as I stated . Low volume.

No exhaust temp alarms? No guardian mode. Time to party!!

[Big Block Power]

By swapping hose outlets you determined flow or volume to each manifold. It changed the temp as a result.
As BB said removing the thermostat will increase flow and bring temps down to at least maximize flow .

You will see the temps drop but it will risk not maintaining good running temps. The reason mfg say that a variance in temp is due to natural flow at low speeds filling a line that has no pressure pushing back.

Everything changes once your underway and the system pressure goes from 1-2 psi at idle ( yep that's all they do) up to 25 psi at 3000 rpm.

The captains call system always steam at idle one side more that the other as I stated . Low volume.

No exhaust temp alarms? No guardian mode. Time to party!!

I agree. I'm not saying to run the boat like that just to try it.

[cmattj]

By swapping hose outlets you determined flow or volume to each manifold. It changed the temp as a result.
As BB said removing the thermostat will increase flow and bring temps down to at least maximize flow .

You will see the temps drop but it will risk not maintaining good running temps. The reason mfg say that a variance in temp is due to natural flow at low speeds filling a line that has no pressure pushing back.

Everything changes once your underway and the system pressure goes from 1-2 psi at idle ( yep that's all they do) up to 25 psi at 3000 rpm.

The captains call system always steam at idle one side more that the other as I stated . Low volume.

No exhaust temp alarms? No guardian mode. Time to party!!

I agree. I'm not saying to run the boat like that just to try it.

Yes we mentioned it just to maximize your low flow at idle. Then put it back in and fire up a lemonade!!

[Silverbullet555]

I'll try it. Not like it's hard to pull a thermo. Hell, I have an extra housing which would the swap quick.

Engine temps have always been fine. Just the exhaust temps.

On a side note. While in the lake in neutral, what's max safe rpm?

Thanks for the replies.

[Big Block Power]

Gxi idles lower than the gi. I think you should be 650 it not advisable though. Your ECU will adjust it with the iac if you play with the throttle stop screw. They are all set to voltages. So don't mess with them unless you know how to read them.
I really don't think you have a problem though.