Overheating 101

Don't know if this will help you, but I had a similar problem on my generator. Was having high temperature issues under full load. Rodded the heat exchanger, flushed the fresh water side, replaced thermostat & radiator cap, rebuilt the raw water pump, and finally measured output flow from exhaust. No joy. My dealer suggested that I might have sediment build up around the lower tubes in the heat exchanger on the fresh water side. He said that flushing wouldn't remove this as it's caked to the tubes. He had a place he sent them to that cleaned them with an ultrasonic cleaner.

I have an ultrasonic cleaner for rebuilding scuba regultors. So I removed the end caps and put it in the ultrasonic with white vinegar (acidic acid ) for 10 minutes. This brown cloud rolled out of the exchanger and I was sure I had either cleaned it or destroyed it. Rinsed the exchanger with water and reassembled the cooling system. Works perfectly now and can run a full load test with 85 degree raw water temperatures without the temperature gauge moving off the minimum.

Not all radiator shops have an ultrasonic cleaner big enough to handle an engine exchanger, but you can probably find one in most large cities.

Ted

My Groco's had drain valves, with plastic plugs and a smallish o ring. Have you replaced your o rings? Your system is sucking in air, same as on the other thread. Thermally, air is about 1000x less efficient than water.

They were recently painted but done properly. No blocking to speak of, paint yes but the grate openings were clear.

diver dave said:

My Groco's had drain valves, with plastic plugs and a smallish o ring. Have you replaced your o rings? Your system is sucking in air, same as on the other thread. Thermally, air is about 1000x less efficient than water.

Click to expand...

These are old SVS-1000's. No plastic plugs. I did replace all of the gaskets from the one under the base, top cover, inside base. Took out the black "rubber" plug and cleaned it up with a few twists in some 120 sandpaper. greased everything up and reassembled. No leaks at all. Just the air getting in...somehow.

I use Rydlyme for cleaning. When I had a yard I flushed a number of boats with heating problems that others had failed to solve. I flush both sides, coolant and salt water. And (as I remember) flushing the coolant side solved the problem in engines with a clean sw side. Rydlyme also dissolves rust and one theory I have is that there is a rust buildup on the cylinder water jackets and coolant passages in the head and block. The rust has an insulating factor that maybe allowing higher temps by restricting the coolant flow thru the engine or allowing much higher cylinder temps.

firstbase said:

These are old SVS-1000's. No plastic plugs. I did replace all of the gaskets from the one under the base, top cover, inside base. Took out the black "rubber" plug and cleaned it up with a few twists in some 120 sandpaper. greased everything up and reassembled. No leaks at all. Just the air getting in...somehow.

Click to expand...

Gotta be frustrating. Would be great to put in 2psi air and do a soap test. Would have to plug the pickup. Somehow.

The frustrating part is thinking they were filling and staying full prior to the haul out/rebuild and now they aren't. Or did they? I think they stayed filled, know I checked them but maybe...??? Just can't remember. I do know that I never noticed and issue but did I really check the water level? ARGGGHHH... I have flushed the RW side, opened up the ends of the HE, was clean to begin with, maybe a little slime of some sort but clean as a whistle now. Hadn't really considered the coolant side. Coolant looks clean but I don't really know what happens in there. Guess I could go ahead and flush that side as well. Right now I really want to go out and see what happens to the level as I ramp up RPM's. I know sitting in the slip with the engines running up to temp they stayed at the same level. It really would explain why perfectly good engines with newer RW pumps, new impellers, and a flushed RW side (at least) would over heat at WOT. Sort of too simple. The not so simple is..WHY? Oh, also going to take the strainers apart and then back together again. Won't help anything but it will make me feel like I did something. Appreciate everyone's help.

My 2 cents that may not be related to your issue. Last spring when we splashed I noticed a similar effect in my strainer, open it and it would fill but start engine and level would drop to a third (what was not the case a year before).
Long story short, we had some issues with the raw water cooling circuit (loose clamp on main raw water main hose that resulted in the hose pop out) and as soon as we fixed it, water level was back to normal in the strainer and we never had any issue anymore.

L

Skippers often have "an attack of the vapors" waiting for the engines to "pass water" relaunching after a haulout. For some reason yours seems not to have returned to previous pumping seawater. What are the chances of an identical issue occurring simultaneously on both engines.
Some random thoughts.Your freshwater side sounds ok, you haven`t been in there, have you? I`d be reviewing the raw water side. Did the strainers go back on ok? Were they cleaned? Could you have made identical errors servicing the seacocks? Are there strainers,are they correctly reinserted? Is all of the strainer below water level so that all of it should fill with/without suction from the pump?
Good luck, sorry you have this problem to contend with. Time to call in a mechanic?

If the engine is pumping water out of the strainer faster than the thru-hull plumbing is allowing it to fill, then the inlet is restricted. Too small diameter, barnacles or other obstruction inside the plumbing, bottom paint blocking hull opening, kinked hose, or partially closed seacock to name a few.
You don't want the strainer running under any significant vacuum. The inlet piping should be large enough diameter to prevent this.

Lou_tribal said:

My 2 cents that may not be related to your issue. Last spring when we splashed I noticed a similar effect in my strainer, open it and it would fill but start engine and level would drop to a third (what was not the case a year before).
Long story short, we had some issues with the raw water cooling circuit (loose clamp on main raw water main hose that resulted in the hose pop out) and as soon as we fixed it, water level was back to normal in the strainer and we never had any issue anymore.

L

Click to expand...

Thanks Lou. I am still thinking User Error so I will go back to almost square one on the strainer, hoses and clamps. As far as I can. Can't take the plug out as I am in the water of course but can verify everything else.

BruceK said:

Skippers often have "an attack of the vapors" waiting for the engines to "pass water" relaunching after a haulout. For some reason yours seems not to have returned to previous pumping seawater. What are the chances of an identical issue occurring simultaneously on both engines.
Some random thoughts.Your freshwater side sounds ok, you haven`t been in there, have you? I`d be reviewing the raw water side. Did the strainers go back on ok? Were they cleaned? Could you have made identical errors servicing the seacocks? Are there strainers,are they correctly reinserted? Is all of the strainer below water level so that all of it should fill with/without suction from the pump?
Good luck, sorry you have this problem to contend with. Time to call in a mechanic?

Click to expand...

Well, they seem to be pumping RW out the exhaust ok. Seems to be the same as prior. If I use my imagination a little and force myself to see a difference I would say...MAYBE a little slower to start pumping it out and MAYBE a second or two between water expulsions? Maybe? Everything went back on, well greased, without incident or problem. Strainers were cleaned and if they aren't inserted all the way the top won't close but they are inserted below the level needed. Both strainers are well below the waterline.

The only other thing not much discussed are the impellers and pumps. Would 10 days out of the water have any affect on either? I just don't think that is it either. I really wish this issue was occurring on one side and not both. That would probably be much easier if you know what I mean. Also wish they were leaking. That would be easy as well.

"one theory I have is that there is a rust buildup on the cylinder water jackets and coolant passages in the head and block."

Before FW cooling was common an engine was expected to have a service life of 6-9 years , before rusting out or rusting up.

While FW cooling and antifreeze can save engine blocks there is still the requirement to change out the antifreeze and CLEAN the engine passages.

Every 3-5 years is common.

The 2 part cleaners do the best job , flush with fresh water numerous times before filling with new antifreeze.

firstbase said:

The frustrating part is thinking they were filling and staying full prior to the haul out/rebuild and now they aren't. Or did they? I think they stayed filled, know I checked them but maybe...??? Just can't remember. I do know that I never noticed and issue but did I really check the water level? ARGGGHHH.....

Click to expand...

I've had a number of strainers, and none contained air during running or standing.

Here is a possible test. Rinse the strainer and seacock with fresh water and dry thoroughly, preferable with compressed air. Let it sit overnight. Then, test for any water on any surface with tissue paper. Any water is a leak.


If that does't reveal anything, here is test #2:
Remove one end of the hose closest to the RW pump. Find a pvc, non-threaded piece that will clamp and seal to the hose. Install a shraeder valve into the pvc plug. Pump the system with a bicycle pump, this will remove all the water from the strainer and seacock. Some small pressure wil exist, since it is pushing out all the seawater. Prepare some soapy water in a spray bottle and hit every surface of the strainer, seacock, and attached hose. Any bubbles will telltail your air leak.

good luck.

Thanks Dave. I need to go slow..not too swift on these things. On your test #1, you are saying to rinse the exterior of the strainer/sea cock, get it clean and absolutely dry and then leave it be. Water appears, got a leak.

Test #2, you mean blow all the water from the system out through the through hull. The air pressure will prevent the water from entering and refilling?

firstbase said:

Thanks Dave. I need to go slow..not too swift on these things. On your test #1, you are saying to rinse the exterior of the strainer/sea cock, get it clean and absolutely dry and then leave it be. Water appears, got a leak.

Test #2, you mean blow all the water from the system out through the through hull. The air pressure will prevent the water from entering and refilling?

Click to expand...

Correct on both. btw, I spent 10 years in Jupiter Inlet Colony, thru high school. Great memories, that inlet.

I am making a few more good memories of the inlet now that I have a bigger boat! Beautiful here even if a little dangerous going out/in some days. I'm inland a little on the south side, right before you make the left to continue down the ICW. Nice to be close ...go to the ocean.. or stay on ICW. Thanks for your comments. Still haven't gotten down to the boat to mess with it. People seem to think that Holiday Parties are more important than the boat. Some people..I tell you...

I purchased a 1999 boat with only 102 original hours on the engine. Had outdrive pulled, new bellows, new impeller, fuel tanks drained, engine serviced etc.
on first “ sea trial” the engine ran great, then stalled and only allowed slow RPMs.
Long story.short, the heat exchanger was blocked and needed to be removed and cleared out with Muriatic acid. Once the HE was replaced the engine runs perfect.
It turns out the Volvo Penta has a “ fail safe mode” that shuts down the Starboard fuel injection if any overheating occurs. It allows you to get home but not at a cruise RPM.
The boat had never been in salt water except to scatter the ashes of the prior owner. It was always in fresh water and yet the HE was fouled.