Temp issues? help please

[bkbaker]

I have an inboard 454 volvo. Sea water cooled. This year we though the boat was running too hot. It showed my coolant was getting as high as 220-230 F. Removed and cleaned the heat exchange, and inspected and changed the impeller. Impeller was intact and felt soft and flexible. Heat exchange was a little clogged with bits of the anode and what looked like small flakes of rock from the Whittier harbor. Still showed hot on the gauge, used a handheld IR thermometer and zapped the heat exchange and manifold risers.

Gauge looks to be bad. Heat exchange showed a max temp of 180 F. The exhaust risers were much hotter, 211 F!!
I have no idea how hot the risers should be. The engine performs well with no loss of power. Can anyone tell me operating temps for the exhaust and manifolds? Thanks in advance.:topjob:

[Daved]

You might have your manifolds or risers clogged with salt and they are backing up the flow of water through the heat exchanger. You are running sea water through both the manifolds and risers? When was the last time they were taken off and inspected? My risers on my jet boat are raw water cooled (not run in salt) they are luke warm. The manifolds on my mercruiser are cooled by the exchanger with coolant and they are around 180 degrees (about the same temp as the coolant) If they were not cooled at all they would be the same temp as the exhaust, like 500-800 degrees? More than 200 anyways. My risers on the mercruiser are raw water and they are luke warm and/or cold. Not sure if you can clean them out or if you have to replace them. They should be easy to get with the correct amount of cash for the 454. Taking them on and off is not rocket science, so long as you have room in your engine compartment to maneuver. My engines have to be lifted out of the boat to change the manifolds. The risers I can do as she sits, and have already one time. Good luck.

[Arcticwildman]

Depending on how many hours you have on the risers, you may not be able to clean them out and have them remain usable. When I pulled the risers on my 454 they were half plugged with salt and metal scale. When I got done cleaning all the corrosion off the coolant passage the walls were so thin I couldn't get the blocking plate to seal.

[bkbaker]

I have taken the risers off last weekend and they look quite good. I scraped a tiny bit of rust off the inside. But no obstructions. Very very minor build up of scale. Second set of risers and manifolds in 6 years. Changed them only for maintenance. Not failure.

The whole system is cooled with sea water. First thru heat exchange then thru the exausht

[bkbaker]

I really want to hear what operating temp for the risers should be. I don't think it's too hot but.

[Arcticwildman]

I don't know the exact temp but they shouldn't be much more than warm to the touch. 211 is way too hot.

[Daved]

I have had a manifold plug up with sand while at idle. It was REALLY hot, like sizzling hot. I had to change the gasket and exhaust hose when I got back home because they fried. So, when they are plugged all the way, they are very hot. When cooled properly they are quite cool to the touch, under the 170 of your engine for sure if running raw water out of the ocean or river. 211 deg seems fishy, like something is partially working. Certain parts of the manifold are further from the water jacket and may be warmer than the rest. There is a place on the inside of my riser that is a lot warmer than every place else, I can still touch it though. Both are like that and is normal operation. Did you take temperatures at several locations on the manifold to see if there was a difference. Otherwise, I still think your manifold is partially plugged, maybe at the inlet. Maybe a hose is plugged, they should be cool to the touch as well since they are running sea water. If the hoses to the manifolds are hot, then I would say you are not getting good water from your water pump, but just enough to cool the heat exchanger and engine but not the manifolds and risers. Aint boating fun???

[bkbaker]

At idle or quickly after returning to idle my manifolds are just warm to the touch. I temped it cool and when I was running at about 3000rpm. I forgot what the cool temp was but at cruise speed I found a spot on the manifold that was 211 F. There are some brass plugs on the top of the risers and I think I may have zapped those with the thermometer. I plan to go out this week with the "cleaned" risers and temp my block as well as the manifolds. Thank you for all feedback. Still love to hear any more input or advice from the motor masters

[potbuilder]

Your raw water pump may be worn out, check to see if it has a replaceable cam, that may help if its worn but usually its better to replace the whole pump. How did the inside of the cover plate look, if it has wear you can flip it over and see if that helps. I had a pump on my volvo diesel that would mysteriously lose prime, i changed impellors, cams & flipped the plate it help a little bit but the real fix was a new pump.

[AKBroncoII]

Were there any grooves in the raw water pump housing? Doesn't take much to cause an issue. I've taken fine sand paper and cleaned them up a bit on a few different engines. Worked perfectly and many more years of usage. Sure beat $400 for a new pump.

[bkbaker]

Thanks Potbuilder. Had the pump in my hands about a month ago. Wish I had just replaced it then. Im getting tired of taking apart the entire coolant system to get to one part or another. Probably put 7 gallons of antifreeze in this year.

[bkbaker]

Were there any grooves in the raw water pump housing? Doesn't take much to cause an issue. I've taken fine sand paper and cleaned them up a bit on a few different engines. Worked perfectly and many more years of usage. Sure beat $400 for a new pump.

Pump internals and face of the plate looked 100%. I wouldn't have changed the impeller except for the troubleshooting.

[potbuilder]

Pump internals and face of the plate looked 100%. I wouldn't have changed the impeller except for the troubleshooting.

You'll never see the wear on the back of the pump with your eyes, it needs to be measured with a micrometer, just a little wear and they don't pump very well. Some wear in the back and some wear on the front cover and you have a pump that putting out less than half. My outdrive guy would put the pump in a lathe and even out the back then take some material off from the flange that the cover screws on to bring the pump back to new clearences, got double life out of those pumps then.

[bkbaker]

Message please? Thanks potbuilder

[Daved]

At idle or quickly after returning to idle my manifolds are just warm to the touch. I temped it cool and when I was running at about 3000rpm. I forgot what the cool temp was but at cruise speed I found a spot on the manifold that was 211 F. There are some brass plugs on the top of the risers and I think I may have zapped those with the thermometer. I plan to go out this week with the "cleaned" risers and temp my block as well as the manifolds. Thank you for all feedback. Still love to hear any more input or advice from the motor masters

Well, there is your answer. Your manifolds were cool to the touch after running 3k, everything looks fine then. You are getting water to them or they would be REALLY hot and so would the motor. You are not overheating the motor according to your gauge. You have a spot that is 211 degrees that is on the top of the manifold, which really is not silly hot unless the whole manifold was that temperature. You addressed the raw water pump, heat exchanger and risers. Those are the big problems with cooling. With the exception of pot builders excellent advice on the raw water pump, you look good to go. Until.......