No raw water suction AQ125

"I changed my impeller not too

"I changed my impeller not too long ago but never tested to see that it actually sucks water. The engine has always ran at about 190 since I got it? What is the normal operating temp?

I just checked for suction and got nothing really. Then I disconnected the hose in the engine comp to bipass the leg (I searched and found the leg could be the problem) so that I could narrow down the problem.

Still no suction. I filled a bucket of water and ran a hose into it, but at idle, at best it is spitting out mist. How much should this be sucking up at 1000 RPM? When I rev it harder it still doesnt really suck up that much... I can't seem to figure out what the problem is, I pulled the impeller again to make sure it is in a clockwise direction, and I pressured the system from the impeller intake and there wasn't one leak. All the water going in went out the leg exhaust.

Thanks!!"

"Check the raw water hose conn

"Check the raw water hose connector in the outdrive, this is likely your problem.

http://www.marineengine.com/parts/part_details.php?pnum=SIE18-2778&returntopage= sierra_marine/sierra00826.htm"

"Hi El, I read about that befo

"Hi El, I read about that before posting, so to eliminate that I ran I hose directly from the intake tube of the impeller into a bucket of water. I still got no suction. There is only so many places it could be bad. The impeller is new, the housing is fine. There is no leaks that I can see when it is pressured and it still will not suck even when I am bipassing the outdrive....."

Are you sure the key on the im

Are you sure the key on the impeller is not slipping?

"OK here is the latest. Took t

"OK here is the latest. Took the boat out today and it overheated to 220 almost. Had to stop. The surprising thing is the impeller seems to be pumping water great! I pulled the filter cap and it was completely full all the time, at idle on the dock it was spewing water from the exhaust! Good...

Now it has never overheated before and since the last time I took it out I changed the timing belt, rebuilt the carb, changed waterpump gasket.

The timing and timing belt are bang on, I checked that when I installed it. The carb could be a little lean maybe? Would that cause overheating? Volvo penta says turn in the mixture screw and back out 1 turn, that seems to be way too lean, I need it out like 2-3 turns min.

Other than that I can't figure out what could be wrong... Nothing has really changed.

One question, is it ok to run without a thermostat! Maybe I will just pull it to maximize flow, and just let the engine warm up a bit more...

Thanks a lot"

"You have a "fresh water&#

"You have a "fresh water" cooling system which is actually two cooling systems. The fresh water side cools the engine and the raw water side (that which gets pumped in thru the leg and out the exhaust) cools the fresh water system via a "heat exchanger". The "filter cap" ( actually the filler cap) is how fresh water (usually mixed with antifreeze) is added to the system. Your test by removing the cap indicates that the "fresh water side" is full of water but gives no indication of the health of the raw water side. Unless the thermostat is defective, removing it won't help much if at all and by and large, fresh water systems tend to run too cool without a thermostat.
What I am curious about is two things...
1) Why did you replace the impeller in the first place and when you did, was it intact? Any pieces missing?
2) How did you get from the post indicating "will not suck when I am by passing the drive" to the point that things were running well enough for.."spewing water from the exhaust" ???? BTW, just because it spews water at the dock does not mean that enough water flows to cool the engine when running under load..."

"After thinking about your las

"After thinking about your last post and my response, I have one more question (To make sure I'm not totaly off in left field)...When you said "pulled the filter cap", what exactly did you remove... Do you have a raw water strainer with a cap? If so, you may have an vacuum leak and be sucking air. In this case, when you removed the cap and looked in, it would still appear to be "full of water"... Also sometimes taking it off and putting it on can improve the seal. You may have a defective seal ring or if the cap is plastic, a crack."

"OK, I replaced the impeller j

"OK, I replaced the impeller just to be safe, wasn't sure if it had been done. The old one looked fine anyways.

When I tested it at home it didn't seem to suck any water, maybe it needed to be primed? But when I removed the fresh water cap it was always over flowing, seemed to be enough flow but maybe not?

I tested it just now at home in another bucket of water and even at 800RPM it is spewing quite a bit of water from the exhaust, which I think is good... The thing is, when i was out on the lake and I opened the fresh water cap the water in there was pretty hot, I could touch it, but it was still very hot. When I tested it at home I ran it for 30 minutes and at times up to 4k RPM, and it never ever felt hot to touch. Plus the Temp gauge never went past 175. Maybe that is because it wasn't under load...

On a side note Robert, do you know how many turns out the air mixture screw usually takes? The manual said 1 I believe but I think it has to be like 2.5 to 3 or else it seems way to lean and maybe makes it run hotter....

Thanks a lot for any help!"

"Hi Jamie, Just to clarify a c

"Hi Jamie, Just to clarify a couple of things, when you say that you took the cap off the fresh water, are we talking about a 'radiator' type of cap? or are we talking about a black screw-on cap that may have a filter basket under it?

The carb comes in two vintages; an old style and a new style. If you have the Seloc manual look at the diagrams on page 4-19. This section outlines the basic settings and procedures to set-up the carb. If you don't have this manual (get one ) you can tell which carb you have by observing the air/fuel mix screw. If the screw goes straight into the carb base, you have the new style and the initial air/mix screw setting is 9 turns out from all the way in. The old style carb has the a/f mix screw at about a 45 degree angle to the carb base. If yours is like this then the initial a/f screw setting is 2 turns out from all the way in. The idle set screw, located a couple of inches to the right of the a/f mix screw, is set by screwing it in until it just touches the carb lever plus 2 more turns in for both vintages.

Remember, when you are adjusting the air fuel mix screw, try to keep the idle rpm as low as possible, just fast enough to keep the engine running. This may require backing-off the idle speed screw from the initial 2 turn setting. This action will limit the fuel scheduled by the throttle setting and all the fuel the engine will see is that scheduled by the air/fuel mixture screw. This procedure should give you a more true setting of the a/f mix screw between too lean and too rich. When you have found the 'sweet spot' adjust the idle speed to desired. "

"Jamie, have you checked if th

"Jamie, have you checked if the impeller key is installed, and if the cross piece (coupling, part 53) is installed between the pump and the auxiliary shaft?

http://www.volvopentastore.com/COOLING_SYSTEM_INDUCTION_AND_EXHAUST_MANIFOLD_AQ1 25A/dm/cart_id.497973580--category_id.333019--list_time.1217925910--session_id.5 99312950--store_id.366--view_id.325811

Also, check that the alternator belt is not loose; for if it is loose, the circulating pump will not work properly.

Also, never run without a thermostat. At best, you would be masking the symptoms instead of dealing with the problem."

"Yes this thread has gotten a

"Yes this thread has gotten a little confusing because my problem no longer seems to be raw water suction . The impeller is doing its job, on land maybe I should have just giving it a few more seconds to prime! It seems to be flowing pretty good.

I think my problem is elsewhere... The cooling pump looks good and the thermo seems to open, so I think I will just adjust the engine to run perfect, to the backpressure test to make sure there is no air ingess, and go from there.

I will write back with the results!

Oh and when i say fresh water or raw water I mean the strainer cap, the pump that brings water from outside. The other one I refer to as coolant cap just to clarify for those wondering...."

"Ok, here is the latest. When

"Ok, here is the latest. When i fixed the o-ring gasket between the water pump and head it squished and ripped a bit which could have cut off some circulation. I have fixed that now properly.

The boat has never overheated before I changed that gasket on a side note...

Further, when I did the pressurization test on the outdrive to look for air ingess I saw leakage from below the elbow joint, I.E. the O-rings... I believe that is a big job to tear apart and I am supposed to go boating in two days for the weekend camping. I really don't want to tear apart my leg

My two questions are, will a couple drops of water coming from the o-ring really cause a lot of problems? I read about how bad it is when I was searching, but I don't think it is ever under pressure like I just put it under with the hose, if I just poured water in there it wouldn't leak out.

Second, the boat has never overheated in the past and I don't think that between the last week that o-ring just failed. So my options are limited to two, A) leave as is for the weekend and hope it will work :S

B) Put in a thru hull cooling system... I read your pros and cons to this and have put in much thought... If I do this I will install a brass thru hull fitting with a raw water strainer and a cut off ball valve for protecting. Where can I locate the thru hull fitting, Could I put it right near the drain plug on the back of a bayliner, basically the center bottom of the the transom, I am worried about cavitation, but I think that area should be ok???

Thanks a lot and I have searched and do realize that it is probably better to keep the stock setup, but, if I do this properly I think it will be an upgrade...."

"Jamie, if your boat has an AQ

"Jamie, if your boat has an AQ125, I guess that 1) it is 25-30 years old, and 2) it has been working until recently without a problem. This is why I am baffled at your suggestion of installing a through-hull system, as it tells me that you prefer to deal with the symptoms rather than attempting to find the problem.

The cooling system in your engine/outdrive is as simple as a pacifier's mechanism. On the raw water side, the raw water pump sucks water through the grids in outdrive, pumps it through the heat exchanger and exhaust manifold, and out it goes mixed with the exhaust gas. On the other side of the system, the circulating pump circulates the coolant through the block, the head, and heat exchanger. There are so many things that can go wrong in the system, and it shouldn't take you too long to find the culprit. If (for the sake of argument) your problem is clogged water passages in the exhaust manifold, a through-hull suction will not only not cure the problem: it will also make you feel pretty bad after you eventually find what the problem was.

BTW, replacing the hose connector and the gasket under it should take you no more than 1/2 hour."

"If the seal under the "st

"If the seal under the "strainer cap" leaks, you may run just fine on a hose or at the dock, but "at speed" you will overheat due to air being sucked in at that point. Typically (I've experienced this when I owned an AQ100) even if the filter assembly is below the water line, it won't leak water, but WILL suck air.
Also per "ELs" previous suggestions, pin hole leaks in the hose from the outdrive to the transom, or in the elbow at the drive will cause the same thing."

"I've pressure tested the

"I've pressure tested the whole system, checked the manifolds, changed all the seals. The elbow connector is not bad, it does not leak from there, it is the O ring below the elbow connector.

Let me state that the engine pumps lots of raw water and it has only overheated once ever. It could have been the seal that was damaged in the strainer cap assembly, it could have been the damaged seal in the waterpump that I mentioned. I fixed both but have yet to test it in the water. What I do know forsure is under pressure, the o ring under the elbow connector leaks, and I really don't want to rip apart the outdrive for that........ I will test the boat again and see what the temp looks like with my recent improvements, if it goes past 190 then I will work some more on it...."

"And further to clarify, the o

"And further to clarify, the one time it did overheat was after I changed the timing belt, pulled the water pump to change a seal, so it very well could have been from those. I believe these engines thermostats don't fully open until 198 so if it stays at 200 i'm not too worried..."

"EP and others, please help me

"EP and others, please help me I'm supposed to go away tomorrow

I just tested the boat and it overheated again.... It never used to overheat, then I wanted to change the timing belt so I did. After changing that and the prop to a 14*`19 from a 14*15 it is now overheating. It overheats not in a plane and in a plane. It seems to have lots of suction now, and it defentely spits a good amount of water out the outdrive.

I'm wondering if the timing belt or the prop made this much of a difference? The engine is not overloaded, at full throttle it does 4800 RPM with this new prop. The engine runs beautiful so I think the timing belt must be on good. I was very careful to aline the marks.

The water pump looked excellent when I pulled it out. Can I use an automotive thermostat for this engine? I will change that just in case it isn't opening properly. I can't really figure out what could be wrong. I have checked everything from the elbow joint out."

"Jamie, how exactly do you exp

"Jamie, how exactly do you expect me to help you? I am not able to look at your engine/drive, but you are.

You say that you have looked at everything, but if that was the case the boat would not be overheating.

How have you checked the manifold? If there is some corrosion obstructing the riser [art or if there is mud/scale inside, then you will need a new manifold, as that one will not allow sufficient water circulation.

And is the engine really overheating, or do you have a defective sender/gauge? An infrared thermometer will tell you what the temperature is in several parts of the engine.

Yes you can use an automotive thermostat (in fact, you have an automotive thermostat installed).

Meanwhile, why don't you give yourself a break and install for the time being again the 14 x 15 prop until you have mire time to look into your problem?"

"Well, i just think it must be

"Well, i just think it must be something i changed. It always worked great, I don't really think it is the prop because i had a 15*21 on there last summer and it never went past 195. I Changed the timing belt and a water pump seal. There are no leaks, so maybe it is my timing... I will retard the timing more tomorrow and hopefully that makes it cooler (retarding does that right?, I believe advancing makes it hotter). I will change to a different prop, and I will switch thermostats. And then hopefully it will be ok for camping trip and worst comes to worse I will just boat and stop let cool boat and stop all the way to the site.

Oh and El, reading through your many posts on this forum it seems your from vancouver island? I'm from vancouver, going to alouette lake tomorrow "

"One last thing. When I remove

"One last thing. When I removed the water pump I removed the heat exchanger. I tried to remove the two bolts that connect the copper pipe to the heat exchangers cap so that I could move that pipe out of the way to remove the bolts. those bolts were stripped in the plastic cap and loosened but didnt come off. Eventually I just pulled the whole cap/strainer assembly. There is a small air gap in that part that connects the copper pipe to the exhaust manifold, could this be a problem? I figure there is no suction there only pushing of water, and it never ever leaks from there... All the same I can't tighten it because it is stripped. Maybe I put duck tape around it as a temp fix to seal it for the weekend, just wondering if that could cause any problems as I couldn't think of any..."

"One more question, I suppose

"One more question, I suppose the temp sender is the same as the automotive version? Probably best to get a new sender as I have no clue about this one, but the engine appears to behave as the temp indicator says so I think it probably is ok"

"I verified it is overheating

"I verified it is overheating with a thermo gun. I also installed a clear plastic hose to check for air bubbles, sure enough there was. I changed the elbow connector and it cleared all the bubbles for a moment and then they returned later. They are not as bad just maybe 5-10% of flow is air bubbles, will that little amount of air cause big problems???"

"Seems she's suckin' a

"Seems she's suckin' air Jamie and as long as she does, she'll likely overheat. Your job is to find where the air is getting into the system and plug it up. In short, you are looking for 0% air bubbles - post again when you achieve that goal and tell us about the temperature."

"This is so confusing. I just

"This is so confusing. I just duct taped the vents on the outdrive closed, put a hose in and pressurized the system. There used to be leaks where the elbow was, now there is no leaks anywhere, but after I replaced the elbow joint I clearly saw air bubbles in the line. There is no leaks so I can't figure for the life of me where they are coming from...

I will go work on this some more. More and more I am tempted in putting in a thru hull fitting, but I would like to try and do this properly first"

Check the metal elbow INSIDE t

Check the metal elbow INSIDE the transom shield. This is the part that the hose to the raw water pump connects to the transom.

"Jamie, if you have verified b

"Jamie, if you have verified beyond any doubt that there are no leaks or obstructions between the intake grid in the outdrive and the suction of the raw water pump, then how do you expect that a through-hull water intake would help? If you are going to work on your boat cooling system, I respectfully suggest that must understand and work with the laws of physics. Alternatively, perhaps you should let a marine mechanic deal with the problem.

Another question, have you checked that the intake grids in the outdrive are clear (not painted on or scaled-up) and there are no barnacles inside? I bought recently a spare leg that came with its own mussel and barnacle farm inside the grids."

1) Just because something

1) Just because something does not leak under pressure does not guarantee that it does not leak when under a vacuum (especially when rubber or fiber is involved).
2) Air will leak thru a hole that water won't go thru.

"I am still in disbelief that

"I am still in disbelief that in over one week since you made the first post you still haven't figured out the problem.

Let's start from basics.

1) The outdrive should not be the problem, but just in case, check:

* That the grids are clear; i.e., not painted on or covered with scale or barnacles. Clean them with a wire brush and a knife if in doubt.

*That there are no barnacles or foreign in the chamber between the intake grids and the pick-up tube. Stick a rod through the drain at the bottom of the leg to make sure.

* That the hose connector is in good condition. Don't just look at it: loosen the clamp and disconnect the S hose, then look at the hose connector. If corroded or rough, replace it.

*Disconnect the S hose from the transom shield tube and inspect it internally and externally. look for cracks, holes, etc.

If OK, then reinstall the hose and you can be assured that neither the outdrive nor the hose connector nor the S hose is the problem.



Now, let's go into the engine compartment:

2) Verify that the hose 20 is in good condition (don't just look, remove it and inspect it thoroughly), that both clamps 19 are tight; that the copper pipe is round (not flattened) and same with the pipe coming out of the transom shield to which the hose 20 is attached, and that there are no holes in either pipe.

Then, make sure the gasket 3 is installed between the copper pipe and the suction side of the raw water pump (that is, the lower port of the pump). Make sure the two screws 47 are keeping the raw water pump tightly in place. And now that you are at it, also, make sure the four screws (part 35) are ataching the pulley to the fresh water circulating pump.

http://www.volvopentastore.com/COOLING_SYSTEM_INDUCTION_AND_EXHAUST_MANIFOLD_AQ125B/dm/cart_id.497973580--category_id.333146--list_time.1218501269--session_id.162591393--store_id.366--view_id.327255

Then, make sure the cross piece 34 is properly installed between the countershaft and the raw water pump:

http://www.volvopentastore.com/CYLINDER_BLOCK_AQ125B/dm/cart_id.497973580--category_id.333147--list_time.1218502314--session_id.074073351--store_id.366--view_id.327291

Now, remove the raw water pump cover and verify that the impeller is in good condition, that the Woodruff key locking the impeller in place is there; and that the cam 10 is installed and locked in place with the screw 11.

http://www.volvopentastore.com/SEA_WATER_PUMP_855578/dm/cart_id.497973580--category_id.333146--list_time.1218502267--session_id.074073351--store_id.366--view_id.327262

If all the above is OK, then the raw water pump will suck water once the boat is in the water and the engine starts. You may want to consider priming it, but it should not be necessary. To verify flow, you may want to disconnect the copper pipe under the exhaust manifold and verify that there is plenty of flow coming out.

Once you verify all the above, we will look into other possibilities if the problem persists."

"Thanks so much for the detail

"Thanks so much for the detailed break down. Here is what I have checked:

The seals going into the raw water pump and the screws are tight. There is no leaks there. The impeller is new and in good shape, it has the cross piece installed the cam part as well.

The vents are clear of obstruction. I will check the long tube tomorrow morning to make sure it is also clear. The elbow joint is new.

When I run the engine with a clear hose it sucks water, but has air bubbles, like I said the connector is new, but maybe the lower O ring is bad or the S hose. To note when I tightened the S-hose clamp on the elbow connector more bubbles appeared??? Leads me to believe that that hose may be my problem. I pulled it and tested it under pressure but could not find any holes, but maybe when it is extended or something there is some pin holes which are causing these problems.

I will replace that hose tomorrow and let you know how it runs.

On a sidenote, I pulled the waterpump and reinstalled it (fresh water) and maybe bolts aren't connected to the pulley as you suggested?? But I don't see how the pulley would stay attached. Is there something that the bolts can grab into but not fully engage the pump?"

"Wow I can't believe this.

"Wow I can't believe this. It is still overheating on me. The S-hose had a small leak, I changed this hose and verified that there are no more air bubbles. Further the flow is great. I am 99% sure my cooling problem is not due to the raw water system... This thread should be renamed

Here is the deal. 3 weeks ago I took the boat out on a monday, it never overheated (actually it has never overheated for the whole first part of the season).

Then i decided the timing belt was 'loose' so I changed it, and while I was at it I found a small leak coming from the seal between the water pump and the head, so I pulled the pump and changed that seal. Well I was at it I rebuilt the carb.

I put it all back together, set the timing to -6, and went for a spin... And starting that day it has overheated. So I am pretty sure it is something I have changed to the system. I believe the air bubbles and that were a problem, but, they were not this major problem... Now I am 100% confident in the Raw water system.

I'm wondering, is there a special way the waterpump pulley needs to be put on? Maybe it is not spinning the water pump well. The water pump was in good shape when I pulled it. Bearings felt great. I also put in a new thermostat...

Or maybe the timing belt is off... The marks that I found to align it were not all that clear... But at the same time I never had to adjust the cam or crank sprockets at all, only the distributor sprocket, and I did readjust the timing afterwards. Maybe when I was tensioning it the crank or cam jumped a tooth, but, I think I clearly saw the marks aligned that were on the belt. What is the likelihood that if the belt skipped a tooth it would cause this overheating and still run great?

I think my problem may be with the closed cooling system. Maybe there was something special I had to do with the waterpump pulley, but I think it just bolts directly to the pump? Maybe the belt is slipping, but again, it is a new belt and it is very tight...

If the engine is running and I take off the coolant cap (closed system), should I see water flowing? (obviously I mean after the thermo has opened)

Thanks for all your help. I pray I can get this figured out before the summer is gone"