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Steam from Exhaust

mybago

Member
"Looking for some help with my

"Looking for some help with my 1990 VP 740A cooling system. I just (last week)replaced my risers and manifolds, thermostat and impeller. When I'm at idle the temp is fine but when I get up on plane then steam is visable coming out of the thru hull exhaust. What is causing this? I haven't checked the oil cooler out yet but I'm thinging that I'm not getting enough water and the water pump might be sucking air with the water when I'm on plane hence the steam. Please help!"
 
The temp started out at 140 wh

The temp started out at 140 when idle then shot up to 180 - 190 after I got up on plane. I'm going to get a better read on it this weekend with a laser temp device. Does both of your motors steam all the time or just when you are over 3K?
 
I've had my boat 1990 Carv

I've had my boat 1990 Carver Allegra with the 7.4 liter and 290DP outdrive for 5 years now. It never steamed at all until last year when it started. The risers and manifolds which I replaced were a mess. I figured that the replacement of the risers and manifold along with the new theromstat and impeller would do the trick. I see that one senior member on this panel where overheating is an issue points to the clamshell on the intermediate housing. If I change that my assumption is that I have to haul the boat? Is this correct. The Oil cooler is another suspect - I never have done anything to this besides spraying it with a "protective" spray.

Hugh
 
"If you did not have steam in

"If you did not have steam in the exhaust before you changed a number of components but now you do, is it possible that something has been assembled incorrectly or one of the components is defective or the wrong one for the application? Just a thought. For example, is the gasket between the risers and manifolds the right one?

Also, keep in mind that in the older Volvo outdrives (270, 275, 280, 290) the raw water hose connector in the intermediate housing is prone to corrosion and the most likely source of air ingress in the cooling system. Make sure you check it if this is your case."
 
"Hugh, you will need to have y

"Hugh, you will need to have your boat high and dry for just about 30 minutes to change the hose connector. No biggie."
 
It did start to steam way befo

It did start to steam way before I changed all of the components.That is what lead me to believe I had an issue somewhere. The risers and manifolds I purchased were already assembled. (came off a engine a while ago and never saw water)I just had to mount them on the block. So I'm not sure if I have the proper gaskets between the manifold and riser for my sea cooled engine?? would the gaskets be
different if they came from a FWC set-up vs. a sea water set up. How about the oil cooler - can that be slowing down my water intake?? Also do I have to pull the boat out of the water to do the raw water hose connector?? Thanks El Pescador.

Hugh
 
I figured that I would have to

I figured that I would have to get it out of the water. When I change the connector is it a good idea to change the hose at that time. Do you happen to have a drawing of the raw water feed from the outdrive to the inside of the boat - I've tried to look at it from the inside and I need to loose 200 lbs and shrink to 3" in order to have a clear view of the rear of the engine.
 
I would have done a test with

I would have done a test with clear armed plastic hoses between transom and cooler before hauling the boat to check for air!
 
The other issue I have is that

The other issue I have is that I have a leak way in the stern of the engine compartment. Could this be the raw water hose/connector also?? It seems like it leaks after I shut the engine down. It is an extremly hard spot to see anything!
 
"Morten,

I have not pulled


"Morten,

I have not pulled the boat out of the water yet. So I will do the "clear hose" test. Should I use a foot of clear hose to see if I can see bubbles in it or can it be shorter?

Thanks
Hugh"
 
"If someone has modified the m

"If someone has modified the manifolds to be fresh water cooled, then the gasket between the manifold and riser has no holes (it is a blank) and the water from the heat exchager is plumbed into the riser. This may not be your case, but I am just pointing about the possibility.

The oil cooler can definitely slow down the flow of water if it is plugged. Because the type that comes from factory is non-serviceable (other than boiling it in acid) you can trt to disconnect the hoses and backflush it. You can also attempt to pass a rod throuogh the tubes, but you will only be able to reach the ones in the center, untless you take apart the cooler and remove the covers, which are soldered.

With regards to the cooling hose between the outdrive and the transom shield, they are not notorious for failing. If it looks good and shows no indications of cracking, etc, I would re-use it.

With regards to the cooling system, you may want to check this link:

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=group&typ e=volvo&group=

I have not seen your engine model, but you may find something fairly similar (AQ290, for example) to give you an idea. You can also try to use a mirror to look at the not-so-visible areas of the cooling system in your boat."
 
Making it somewhat an inverted

Making it somewhat an inverted 'U' makes it easier to se if an air buble is building. How long depends a litle about space in engine room.
 
Fo not forget to check your po

Fo not forget to check your power steering cooler (if installed).
 
"<u><font color=""ff0000"">[b]

"<u><font color=""ff0000"">Do</font></u> not forget to check your power steering cooler (if installed)."
 
El Pescador

I will check e


El Pescador

I will check everything you mentioned this weekend. Is there anything else I need to check as far as the cooling system goes?

Thanks
Hugh
 
"Nothing, except making sure t

"Nothing, except making sure that the grids in the lower unit are clear (no corrosion/scale building up). Also, you may want to follow the advice given by Morten about an inverted u-tube, as this will tell you if you are sucking air when you take your boat for a test drive. It may also be helpful to bring a laser thermometer with you and check whether the exhaust temperature is abnormally high, which would confirm poor water circulation or plenty of air mixed with the raw water.

Good luck."
 
Reply from Hugh Reid sent to m

Reply from Hugh Reid sent to me as email by mistake:
<blockquote><hr size=0><!-quote-!><font size=1>quote:</font>

What temp would you consider to be "high"for my RWC engine from the laser thermometer.

Also should I take the temp after a short ride on plane - or when I'm actually on plane which would require me to have the hatch open. I'm sure that the grids are clear since I made sure they were clear and cleaned and protected before I had it put in the water. Is it possible that barnacles made it thru the water intake slots and are blocking the flow of water above the slots and below the actual intake on the transom?

Thanks so much for all of your advice and also Mortens. I will do the inverted U thing also. One last question - if I take the two ends off of the oil cooler will I have any issues with oiutside water coming in? I have thru hull exhaust. I also remember that you said if I had a power steering cooler to check that. Were would that be if I have one.

Again thanks so much for taking the time to help me.

Hugh
Hugh Reid<!-/quote-!><hr size=0></blockquote>
 
"As a general rule, I would ex

"As a general rule, I would expect the water temperature in the block to be between 160ºF and 190ºF. I would be concerned of anything higher. In any case, you may want to consider downloading from the Volvo Penta site the owner's manual for your engine from this link and see what their recommendation is:

http://www.volvo.com/volvopenta/global/en-gb/marineengines/operators_manual/


You can also download a brochure for your package from here:
http://www.volvo.com/volvopenta/global/en-gb/marineengines/older_engines_1/2002/ gasengine/sterndrive/

You should take the temperature when your engine is loaded; that is, on the plane. You may want to consider having a second person in the boat to check the temperature while the other one steers the wheel.

Regarding barnacles in the cooling system, the possibility is there, I have seen a few cases.

If you want to disconnect raw water cooling hoses while the boat is in the water, you have to make sure you are not going to flood the engine compartment by verifying that you can put the open end of the hose above the water level. If you are not comfortable doing it on the water, you can always put your boat on a trailer.

According to the above brochure for the 740 through-hull package, the steering oil cooler should be positioned port side aft of the exhaust manifold and before the engine oil cooler."
 
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