Reduced water flow? Help??

[John D]

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M



john_dupras@hotmail.com

[Bill DeCamp]

John I had the same problem on our CD28 #342, I pulled the thermostat and found alot of pieces of neoprene which came from broken off impeller vanes from the water pump. I fished these out and replaced the thermostat and flow and temp range was normal and has remained so. I'd be leery of the acid treatment. the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

tocoiriverrats@aol.com

[Larry DeMers]

Sounds to me like a faulty thermostat..or a plugged one. These critters are known for this..mine did it (the same thing) two years ago.

I would not run the engine without the water injection going also, as that acts to cool the exhaust hose, and is needed in order to avoid damage to the hose. What you could do..and this is what the dealer did when I test ran the engine on our boat when i bought it 11 years ago, is to place a bucket with a hose in it's bottom such that it would pick up the water sent out the exhaust, drop it donw the hose into a second bucket. When that bucket filled up, it was handed up into the cockpit for recycling into the engine water intake. However, I would ask a couple mechanics about using an acid on this engine..perhaps there is a better chemical available.
Try the thermostat removal, cleaning if needed, replacement if needed (try it on the stove!) path first.

Cheers!

Larry DeMers
s/v DeLaMer
Cape Dory 30

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

demers@sgi.com

[chuck yahrling]

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

To test and/or clean your thermosat, remove it from the housing and chip any loose scale away from it. Ditto for visable scale in the housing and water jacket.

Gently heat the thermostat in a small pan with household vinegar to a gentle boil until it looks clean. Rinse with fresh water. If you have a kitchen thermometer repeat with a fresh water bath, noting the temperature when the 'stat starts to open, and when it is fully open. Then let it cool off, noting the temp when it is closed. Compare with normal temps, which you can get from a shop manual or friendly mechanic. I compare the "start open" and "fully closed" temps and average them if different but close.

If either the high or low is off by more than 10 degrees I would retest and replace the 'stat with a new one if it's really off. So far I haven't had to replace the thermostat in Samhain's 2GM.

I inspect the 'stat for gunk every season, since I remove it to make sure antifreeze gets into all the water jacket passages when winterizing. It's nice to know I can remove it in a few minutes if it ever got stuck closed.




cyahrlin@ cisco.com

[John D]

Larry - Thanks for the insight, it seems to be a consensus to check the thermostat first. Just curious, why would that reduce to output? Shouldn't the same amount of water com out of the exhaust and the engine just run hot? I guess I don't understand how these things work vary well. Thanks.

John Dupras
S/V Mariah



john_dupras@hotmail.com

[Matt Cawthorne]

John,
The passages on raw water cooled engines will eventually begin to get gunked up in salt water. My brother has a volvo (MD8a?) in his boat and after about 20 years it always ran on the hot side. He changed the thermostat without any improvement. He eventually took it to a diesel shop and they removed the head and cleaned out all of the passages. It now runs much cooler.

The cheap and easy solution (thermostat) is the one you should try first.

matt



mcawthor@bellatlantic.net

[Larry DeMers]

John,

The thermostat has a small hole drilled into it's body that allows some water to circulate past it regardless of the position of the bimetal spring operated valve. So it stays shut until your water temp gets to around ~160 deg., where it will start to open, and by 190 deg. it should be open fully.
It would make sense for the water diverted away from the engine by the thermostat, to go into the mixing elbow and be exhausted overboard as usual. In fact, I do believe that the water flow I observe from the exhaust remains the same regardless of the thermostats position, which implies that this is true.
The thought that occurs to me is that you may have broken impellor vanes trapped in the bypass passageway, which reduces water flow through the thermostat. Removing the thermostat would be the only way to check this.

One thing that we had happen once..after sitting all winter, our impellor (which was not removed and exchanged that year) had a problem with a couple vanes which were flattened out. This decreased the pumping efficiency a lot, making the enemic trickle of water on the MD7B even less. This would allow the engines heat to build up more and give you fits trying to solve the problem.

Larry - Thanks for the insight, it seems to be a consensus to check the thermostat first. Just curious, why would that reduce to output? Shouldn't the same amount of water com out of the exhaust and the engine just run hot? I guess I don't understand how these things work vary well. Thanks.

John Dupras
S/V Mariah

demers@sgi.com

[Jody Kaplan]

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

Hi John,I Experienced a lack of good flow out exhaust,mine had a clogged thermostat housing,manifold,hose(pipe)leading to manifold.The passages were well clogged.I have the same engine-1979.Good Luck Jody K



jody_kaplan@hotmail.com/

[sloopjohnl]

if you or your mechanic is going to remove the old thermostat to have a look see, throw the old one out and install a new one. don't even mess with the old one considering the cost of a new one; old or new, one of them has to be re-installed anyway. save the old one to soothe your curiosity when you have absolutely nothing else to do!!!

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

[Michael Abramson]

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

John,

I have the exact same boat and engine combination. On my boat, the
raw water inlet hose goes to the transmission first, where it passes
through a water jacket and then on to the engine water pump. It is
possible marine growth has occured inside this jacket, or possibly
some grunge got past the thru-hull screen and has lodged there.

The thermostat housing is relatively easy to remove and inspect, but
be sure you have the inner o-rings on hand first. From memory there
are a couple including a conventional round section one inside the
cast housing and a rectangular section one for the water pipe to the
engine. This is a 3-hand job to put back on, since the inside one
wants to fall out when you are reinstalling the housing. Use a bit
of white grease to hold it in. The genuine Volvo t'stats are about
$20, I've heard you can find an equivalent at NAPA. If you order
from a Volvo place, be sure to get a couple extra rubber seals that
go around the stat.

I suspect if you have a markedly reduced water flow, there is a
blockage, it is probably not a scale deposit that has built-up in
just one season.

Michael Abramson
CD Intrepid 9M Peace
Yorktown, Va



mabramson@widomaker.com

[Andrew Blight]

John:
I would check first the possibility that you have a blockage in the cooling system rather than a problem with the thermostat. My MD7A ran hotter than it should for a while and then began to really overheat. I found that when I tried to flush the system there was a ton of accumulated scale. Once it was removed, the engine ran cooler than it ever had before. I used a T-connection (such as comes with some brands of radiator flush) permanently installed on the inlet hose, and connected it to the dock water hose. I removed the impeller, replaced the cover, and disconnected the main hose to the water-lift on the muffler so that there was a way for the water to escape safely into a collection bucket. There was a lever operated spray on the hose from the dock supply, and this allowed very high pressure bursts of water to be applied with instant control. It took some time to get the junk to clear the system, but the results were quite impressive.
Best of luck with whatevery you try!

[John D]

Hi John,I Experienced a lack of good flow out exhaust,mine had a clogged thermostat housing,manifold,hose(pipe)leading to manifold.The passages were well clogged.I have the same engine-1979.Good Luck Jody K

OK Jody, what did you do to clean the passages?

John



john_dupras@hotmail.com

[John D]

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

John,

I have the exact same boat and engine combination. On my boat, the
raw water inlet hose goes to the transmission first, where it passes
through a water jacket and then on to the engine water pump. It is
possible marine growth has occured inside this jacket, or possibly
some grunge got past the thru-hull screen and has lodged there.

The thermostat housing is relatively easy to remove and inspect, but
be sure you have the inner o-rings on hand first. From memory there
are a couple including a conventional round section one inside the
cast housing and a rectangular section one for the water pipe to the
engine. This is a 3-hand job to put back on, since the inside one
wants to fall out when you are reinstalling the housing. Use a bit
of white grease to hold it in. The genuine Volvo t'stats are about
$20, I've heard you can find an equivalent at NAPA. If you order
from a Volvo place, be sure to get a couple extra rubber seals that
go around the stat.

I suspect if you have a markedly reduced water flow, there is a
blockage, it is probably not a scale deposit that has built-up in
just one season.

Michael Abramson
CD Intrepid 9M Peace
Yorktown, Va

Thanks Michael - is there a way to check the water jacket around the tranny? You may be on to something here as the water that has been coming out is reddish in color, not like oil but the same reddish color I get when I scrub the bottom ant the slimy stuff mixes with the water around the boat. Could be a mass of some slimy stuff got in there and is stuck. How would I "unstuck" it? Any idea? Thanks.

P.S The boat is "new to me" and is our first. How does yours handle in a good breeze, heel angle wise and weather helm wise?

John
S/V Mariah



john_dupras@hotmail.com

[John D]

John:
I would check first the possibility that you have a blockage in the cooling system rather than a problem with the thermostat. My MD7A ran hotter than it should for a while and then began to really overheat. I found that when I tried to flush the system there was a ton of accumulated scale. Once it was removed, the engine ran cooler than it ever had before. I used a T-connection (such as comes with some brands of radiator flush) permanently installed on the inlet hose, and connected it to the dock water hose. I removed the impeller, replaced the cover, and disconnected the main hose to the water-lift on the muffler so that there was a way for the water to escape safely into a collection bucket. There was a lever operated spray on the hose from the dock supply, and this allowed very high pressure bursts of water to be applied with instant control. It took some time to get the junk to clear the system, but the results were quite impressive.
Best of luck with whatevery you try!

Andrew - That's why I love this board! I probably could have gone years without ever thinking of something like this. Im sure willing to give it a try. Another advantiage would be that when she was going to sit for a while, I could put fresh water instead of salt water in the block and delay the corrosive effects. Have you had any issues with the T fitting? is it plastic or metal or what? Thanks a lot.

John D
S/V Mariah



john_dupras@hotmail.com

[Joe Sankey]

John: I am not familiar with your engine. I had a Universal 18 (FWC) in a 28, and went through the entire system (I thought) looking for the cause of overheating. I checked seacocks, impeller, thermostat, heat exchanger and exhaust. Eventually we checked a small reinforced hose leading from the thermostat housing. It had delaminated at the wire reinforcing and was acting as a check valve as the engine rpm increased, thereby restricting flow to the engine. If you haven't checked hoses, you might consider it.
Joe

OK -First the basics - I have a 16 year old Volvo MD7A that over the past few weeks seems to be running hot and has a less than usual water flow out the exhaust. The impeller is good, the water into the boat through the seacock as well. 2 main questions - could it be a thermostat problem? Perhaps a plugged passage? (It's raw water cooled). I have heard of a product called marsolve (www.marsolve.com) that claims to be able to descale, delime, derust etc, like mauratic (sp) acid, but no harmful side effects. Anyone tried this stuff? The sales guy said you can uses a 5 gallon bucket and suck in into the engine, out the exhaust injection hose back to the bucket for a half hour or so. Wouldn't that cause a problem with the boat exhaust system? Don't you need that injection to the waterlift muffler to avoid major problems? I don't know much about engines, (but I'm about to get a crash course I bet), so any info, insight, prayers etc would be appreciated. Any other information I can provide I'll try, and any ideas of anything else to check I'll try them as well. Thanks a lot folks.

John Dupras
S/V Mariah
Intrepid 9M

sankey@gulftel.com