2005 Volvo Penta 4.3GL Overheating

[bl_kamaji]

The issue : (2005 manufacturer date) Volvo Penta 4.3GL started overheating a couple hours into our day on the river.


Story : Engine overheated about 2 hours into our poker run on the Ohio river. Let the boat cool down to about 130°F before starting again. Tried to make it back to the ramp using low speed, engine quickly heated up to 200°F. Shut off and got towed in. We did stop at a couple sand beaches where we used a T bar to secure the boat. Trim was always fully up. Not sure if we sucked in sand or not.

What I've done so far : 1. Visually checked intake screens on sterndrive for blockage. 2. Checked the impeller and thermostat, both which were in seemingly working order. The thermostat was cruddy looking so I will go ahead and replace it. Click this link for photos. https://drive.google.com/folderview?...B65QG7XlkcuJaM

I'm a new boat owner and complete novice. Looking for advice on what the next steps should be? (Please, no sarcastic answers). Can provide pictures and videos as needed.

 

[tpenfield]

:welcome: to iBoats . . .

Not a Volvo-Penta expert, but check the intake hoses leading all the way up to the thermostat housing to see if there are any oil coolers along the way. Often marine life gets stuck in the coolers, blocking the flow of water to the engine.

The thermostat housing looks like there is a fair amount of rust/corrosion build-up in some of the passages. Clean that out as well.

 

[Lou C]

Who worked on the thermostat last? Looks like someone tried to install the stat like an auto stat, was it retained in the stat housing by the rubber ring? Could not tell from photos. If the manifolds and elbows have as much corrosion as the thermostat housing they could be getting clogged.

 

[bl_kamaji]

Looks like someone tried to install the stat like an auto stat, was it retained in the stat housing by the rubber ring? If the manifolds and elbows have as much corrosion as the thermostat housing they could be getting clogged.

The thermostat was retained by the rubber o-ring. I plan on cleaning the rust and corrosion out of the housing before reinstalling.

Someone recommended an engine flush. Do I just simply hook a hose to the blue flush port on the engine? I have the workshop manual and the owners manual so I'm hoping the instructions are clear.

 

[cptbill]

Take the hose off the fresh water pump (the one that leads to the transom) and se if water comes out, the put some flushing muffs on the outdrive covering the water intakes and turn the water on, if you get good water flow your problem is isn't from the outdrive to the fresh water pump. Put the thermostat in a pot of water on the stove and see if it opens(I would just replace it since you already have it out) Make sure your impeller is not just spinning on the shaft and that all your passages in the thermostat housing are open. The problem could also be the engine water pump(most of the time they leak water but sometimes the impeller goes bad) Don't forget to pull the spark plugs to make sure the cylinders don't have water in them and also check the oil for contamination

 

[bl_kamaji]

Take the hose off the fresh water pump (the one that leads to the transom) and se if water comes out, the put some flushing muffs on the outdrive covering the water intakes and turn the water on, if you get good water flow your problem is isn't from the outdrive to the fresh water pump. Put the thermostat in a pot of water on the stove and see if it opens(I would just replace it since you already have it out) Make sure your impeller is not just spinning on the shaft and that all your passages in the thermostat housing are open. The problem could also be the engine water pump(most of the time they leak water but sometimes the impeller goes bad) Don't forget to pull the spark plugs to make sure the cylinders don't have water in them and also check the oil for contamination

I'll need to start the engine at some point during this procedure, right? Assuming once I turn the water on.

Also, the impeller housing and thermostat housing (which already passed the hot/boil water test) are currently off of the engine. Should I basically put everything back together and THEN run water? Like I said before, 100% novice, but can follow instructions.

 

[bl_kamaji]

I forgot to mention that the circled item (located on the STARBOARD side) in the photo was super hot. The coating on the outside looked like it was melted. Maybe this helps diagnose.

 

[tpenfield]

Yes, helpful . . .

The green arrows in the picture below are the places to look and clean out . . .
.

 

[Scott Danforth]

start at the raw water pump and back-flush the hose going out the drive. that should blow out the debris you sucked up into the oil cooler

also, check the condition of the fitting where the raw water hose connects to the drive.

pull the impeller

back-flush the motor from the exhaust manifolds to the raw water pump

open the manifold drains and drain out the debris. flush out as needed

open the block drains and drain out the debris. flush out as needed

replace the impeller with a new one.

 

[cptbill]

I forgot to mention that the circled item (located on the STARBOARD side) in the photo was super hot. The coating on the outside looked like it was melted. Maybe this helps diagnose.

No, your just trying to make sure you have water flow, really sounds to me like your not getting water flow into the manifolds and possible else were. The diagram above should help you find places where flow can be restricted, and Scotts advice is sound also.

 

[Lou C]

On these open systems they are not pressurized like a closed cooling system so they depend on a high volume of water IN and OUT to keep the exhaust at normal temps. My engine has the same exhaust and thermostat housing but a different raw water impeller (OMC Cobra, impeller is in the drive). Had it out today so I can give you some temps of what it should run at:
Temp gauge, usually 160 it may drop slightly when accelerating on plane and may rise slightly when slowing to idle after coming off plane. I usually take IR temp readings on the intake manifold right under the stat housing and it will usually be around 135-145*F, when the dash gauge reads 160*. The exhaust manifolds will read about 95* at idle. After coming off plane they will be between 125-135 but will quickly cool down after idling for a few min. The part you circled (exhaust 90* adapter pipe) at idle is between 95-110*. So either you are not getting enough cool water IN, or clogging in your manifolds and elbows is not allowing hot water OUT.
If the paint on that exhaust adapter pipe got hot enough to start melting the rubber exhaust hoses may be melted inside too. I would be draining the exhaust manifolds and removing them and the elbows to inspect the water passages. If they are clogged by rust replacement is needed, and you may need to replace those exhaust hoses (rubber) if they are burned inside.
What a new Volvo manifold looks like:

 

[Lou C]

Manifold cooling passages

 

[bl_kamaji]

On these open systems they are not pressurized like a closed cooling system so they depend on a high volume of water IN and OUT to keep the exhaust at normal temps. My engine has the same exhaust and thermostat housing but a different raw water impeller (OMC Cobra, impeller is in the drive). Had it out today so I can give you some temps of what it should run at:
Temp gauge, usually 160 it may drop slightly when accelerating on plane and may rise slightly when slowing to idle after coming off plane. I usually take IR temp readings on the intake manifold right under the stat housing and it will usually be around 135-145*F, when the dash gauge reads 160*. The exhaust manifolds will read about 95* at idle. After coming off plane they will be between 125-135 but will quickly cool down after idling for a few min. The part you circled (exhaust 90* adapter pipe) at idle is between 95-110*. So either you are not getting enough cool water IN, or clogging in your manifolds and elbows is not allowing hot water OUT.
If the paint on that exhaust adapter pipe got hot enough to start melting the rubber exhaust hoses may be melted inside too. I would be draining the exhaust manifolds and removing them and the elbows to inspect the water passages. If they are clogged by rust replacement is needed, and you may need to replace those exhaust hoses (rubber) if they are burned inside.
What a new Volvo manifold looks like:

That is excellent information! I pulled the drain plugs that are underneath the engine (block drain plugs?) and had to use a small screwdriver to clear the sand for it to drain. I'll take that manifold and hose off and check there for debris as well. Will check back in after.

 

[bl_kamaji]

https://drive.google.com/folderview?id=1DWZ4vGLs50FatbkijpV-RVApw0KKpHTr

So I pulled both drain plugs from the bottom of the engine and there is definitely sand in there. I flushed it out the best I could. The engine still starts up fine. So that's a plus. When it runs on muffs (no thermostat right now) the large hose coming from the thermostat housing and the top of the manifold riser gets hot very quickly. At idle. I have included a link with more pictures of what I have apart. Water SEEMS to flow fine when I back flush. But the problem appears to be isolated somewhere in the starboard side exhaust.

 

[bl_kamaji]

Just a thought. Is it possible that the clog is somewhere AFTER the exhaust? I don't know exactly where to look on the Stern drive for where it all comes out at.

 

[tpenfield]

Did you ever go through the thermostat housing and clean things out, particularly the by-pass duct?

 

[Lou C]

The manifold and riser look very clean I’d think your restriction is either before or after. I’d test the flow of each side individually by hooking up a garden hose to each manifold and compare the flow you get out back by the transom mount/exhaust bellows. That and compare the out put from each side of the thermostat housing. The manifolds and risers should run at about 90-100* at idle and after coming off plane they can go as high as 135* but will come back down after idling s few minutes.