volvo penta 170 overheating

[tomcatdsl]

Just bought '76 fiberform 28 with twin volvo 170s. Both w/ problems. Will start with port engine. Overheats when running even at idle. However, when I take off the sea water filter, and run a garden hose into the system w/ cold fresh water, running temp returns to normal. Took a plumber's snake and ran it the oppostie way to the intake as far as I could into the outdrive,(Probably not far enough I guess) to check for obvious obstructions. No luck. Ran the garden hose water stream out through the outdrive intake line and it (the water stream)would come out the exterior of the outdrive, so I thought the water intake at the outdrive was now open. Put it all back together with high hopes, and lo and behold, when it ran for a while (5-10 minutes), it began to run hot again. Anybody w/ any bright ideas? Previous owner said he had just put in a new impeller. Wrong one maybe? Sticky thermostat? I'm confused.<br /><br />Thanks,<br /><br />Tom

 

[Dunaruna]

Re: volvo penta 170 overheating

Hi Tom,<br /><br />Are we talking about FWC or RWC?, the 170 could have either.<br /><br />Aldo

 

[tomcatdsl]

Re: volvo penta 170 overheating

Aldo,<br /><br />Duh, I didn't say did I? It's RWC. That's why I thought raising the outdrive and scrubbing off what I could get off externally, (it's in the water, in a slip), and trying to force water backwards through the RW intake from the filter mechanism. When it took the water and I could observe it exiting the intake port, I thought the problem was solved, but no such luck. Could it be that the impellor isn't drawing enough vacuum to draw the water in through the pipes? The guy I bought it from said he just put in a new impeller, so it shouldn't be that, unless he put in the wrong one or something, and it isn't doing the job. For the moment, I'm kind'a at a loss. Any thoughts?<br /><br />Tom

 

[Dunaruna]

Re: volvo penta 170 overheating

Tom, My monies on the raw water pump, if it was me, I would check his work and inspect the pump. Old impeller bits can get caught up in the system (causing a blockage) and the impeller housing can wear.<br /><br />The way I read your post you disconnected the hose at the transom and ran a garden hose to the outside, right? What about the other way, use the garden hose to run water towards the pump, if its not blocked, water will exit through the anti-ventilation plate (just above the prop) but you've gotta have the thermostat removed to do this. <br /><br />Another area that gives trouble is the 's' shaped hose and steering pivot water tube under the uni's bellow. If they are worn they will allow air to enter the system, the efficiency of the pump will be greatly reduced.<br /><br />Aldo

 

[tomcatdsl]

Re: volvo penta 170 overheating

Aldo,<br /><br />Thanks for the suggestions. You've given me a couple of things to check. Question....There is a sea water filter in line before the waterline that leads to the raw water pump. What I did was to open that rascal up and run water from the garden hose into the system upstream from the pump. When I did this, the temp gauge returned to normal range and the water outlet that you were referring to, "the antiventilation plate above the prop had a narrow stream of water flowing from it. It looked like it was peeing. YOu were saying that the thremostat had to be removed in order to eval that, but I think it had opened earlier, becasue of the initial warm up of the engine before the system would accept any water or else after the engine warmed up from not having coolant flow over the thermostat. The reason I say this is because at first, water would not flow into the raw water pump and I thought that was the problem, that the pump was not accepting water flow. Then, all of a sudden, water began to flow into the system, and the pump began to work. Does that mean that the thermostat opened? If that was the case, would it then follow that the loss of flow had to be upstream from the sea water filter? What you said about a worn s tube or steering pivot water tube under the Uni's bellows being worn and allowing air into the system thereby reducing the pump's efficiency sure could be. Wonder if I put a new raw water pump on the old girl and checked for water flow, and if it still wasn't very good, then replace the s tube and steering pivot water tube as the next step. Then I would at least know that they raw water pump was not a problem for a while to come. The s tube, if I am thinking of the right do-dad, on this boat appears to be metal, possibly copper. I'm going to have to look for the stearing pivot water tube. Not quite sure if I have seen that one yet. Do you think it would be better to attemtp to replace the raw water pump and see what effect that has, and then look to replacing the s tube and sterring pivot water tube if the new pump doesn't do the trick? Or would it be better to replace the tubes first and then see how water flow may be effected? Probably the second way would be more economical, if the raw water pump is not the real culprit, eh? Tubes first, pump second?<br /><br />Thanks for taking the time to advise!<br /><br />Tom

 

[Dunaruna]

Re: volvo penta 170 overheating

Sorry Tom, I didn't realise you were doing the flush with the motor warm. What you are describing sounds like the thermostat opening at the right time. The pump is a vaccum pump, when you add a garden hose into the seaweed filter you are cancelling out the need for vaccum, in other words you are bypassing the need for a pump, hence the temp falls. You've got a pump problem.<br /><br />I not sure what you mean by 'metal tube', on the picture number 54 is the 's' hose I referred to.<br /><br /><br />

<br /><br />Take a copy of the picture if you want and then I'll remove it.<br /><br />Aldo

 

[tomcatdsl]

Re: volvo penta 170 overheating

Aldo,<br /><br />Thanks! I'll change out the pump and see what happens. You had mentioned that the housing might be worn too, so may as well pull and replace. Do you think a generic one would be fine or should I use the factory replacement?<br /><br />Thanks for all your help! I have some more questions for you on the Starboard engine once I get this port rascal working. Thanks again!

 

[Dunaruna]

Re: volvo penta 170 overheating

Some people may disagree but I don't have a problem with generic pumps (VP never made pumps anyway). You need to inspect the housing and seals carefully, sand can do a lot of damage and heat can warp the impeller housing. I like to play it safe and replace the whole pump but its your call. <br /><br />Their are a lot of senarios that can cause symptoms similar to a pump failure: blockages, lose belt, air getting into the system etc. The raw water pump is a part of the system that requires periodic replacement but it's only a part of the system. Other things can and do fail. Keep us posted.<br /><br />Aldo

 

[tomcatdsl]

Re: volvo penta 170 overheating

Aldo,<br /><br />Thanks again for your excellent advice.<br /><br />According to which, I pulled the face off the raw water pump tonight, and lo and behold, the impellor was chewed all to "you know what"! It either was a bald face lie that the guy had changed it recently or they sold him a defective or incorrect unit. It had a bit of corrosion on the metal parts, but the rubber parts looked aged, so maybe the guy got sold a bad one or else he was not wholly up front with me. I'll be visiting my local marine supply store tomorrow to see what they have to say. Hopefully that's all it is. Just to reassure myself, I hooked up the garden hose again tonight, to the raw water intake from inside the transom, and turned the flow up all the way, and it flowed out to the exterior very freely, so I think your diagnosis is correct, it's a pump problem. I will indeed keep you posted. If this solves it, I will have another probelm to pick your brains about with the starboard engine, but one step at a time, right?<br /><br />Thanks for your help!<br /><br />Tom

 

[Dunaruna]

Re: volvo penta 170 overheating

Originally posted by tomcatdsl:<br />[QBlo and behold, the impellor was chewed all to "you know what"! It either was a bald face lie that the guy had changed it recently or they sold him a defective or incorrect unit Tom [/QB]

or he put the blades in the wrong direction <br /><br />Aldo

 

[tomcatdsl]

Re: volvo penta 170 overheating

Aldo,<br /><br />I might make the same mistake, if that was it, how does one tell which way the blades should go? In fact, is there a guide somewhere for replacing an impellor? It didn't look like the guy put in any new gaskets either. Nice work, eh? Got any guidance for me on replacement of the impellor?<br /><br />Thanks,<br /><br />Tom

 

[Dunaruna]

Re: volvo penta 170 overheating

Tom, <br /><br />A new impeller is bigger than the housing, the blades need to bend to fit in. Rather than run through the procedure I'll give you this link, it explains everything.<br /><br /> Impeller replacement <br /><br />This picture shows shows how the blades bend, this pump runs clockwise (facing the front). Your motor runs clockwise looking from the front.<br /><br />

<br /><br />Don't be afraid to use plenty of rubber safe lubricant.<br /><br />Aldo

 

[tomcatdsl]

Re: volvo penta 170 overheating

Aldo,<br /><br />Thanks for the info! Good stuff.<br /><br />Here's the latest news. Yesterday, I removed and replaced the impeller, taking the chewed up one to the store and bought a replacement. Put the new one in, and tested the system. But to my frustration, it still heated up and over heated. So I stopped, took the pump apart again, and the newly replaced impeller was already chewed up too! So I took the entire pump off the engine and too it to the store with me and the part man said it was the wrong size impeller in the first place! So he sold me a different one, slightly smaller, I went back to the marina and installed the newer impeller. Fired her up and the temp still ran up way into the red! So once again, I took the sea water filter apart with the engine running, and put my thumb over the hole leading to the intake of the water pump, and there was hardly any vacuum at all! Certainly not enough to pull a column of water through the system. Now what do I do?<br /><br />I started looking for obvious vacuum leaks and did not find anything really. Could it be the other pump, the circulating pump, rather than the raw wqater pump? Supposedly, there is a second pump called the circulating pump, deeper in the guts of the engine. But that wouldn't explain the lack of vacuum at the exit of the raw water filter going TO the raw water pump, would it?<br /><br />Once again, I'm stumped at the moment. I did consider just replacing the raw water pump altogether, priced it and noticed it was $730.00!!! WOW!!! If that's what it takes, that's what it takes, but ouch! And what if that still isn't the problem? I'd hate to slap a $700 new pump on and then see that there still wasn't enough suction to pull the water into the system.<br /><br />Any other suggestions? Just to check for obstructions again I ran the garden hose into the exit hole of the sea water filter towards the raw water pump, and once again, the engine temerature dropped back down into the normal range. So it doesn't look like there's any obstruction downstream from the raw water pump. There's just not enough vacuum, for what ever reason, to get the water to flow through the system via the pumps, either the raw water pump or the second "circulating" pump. It's not immediately clear to me from looking at the diagrams just exactly whre the circulating pump is, but it is shown in three dimension on one of the engine diagrams. I'll have to look more closely and see if I can locate it. Do you think that could be it, or is it still the raw water pump? Which pump is responsible for providing the greater part of the vacuum? If there is vacuum loss in the line somewhere, where is the most likely place to check for it?<br /><br />Thanks again for your patient help.<br /><br />Tom

 

[Dunaruna]

Re: volvo penta 170 overheating

Let me give you a quick overview (6cyl VP raw cooled). Water enters the vents at the bottom of the leg, up through the center steering pivot into the 's' shaped hose and through the transom plate to the raw pump. The raw pump pumps it to the oil cooler and block, if the thermostat is closed the water is directed to the exhaust manifold (small bleed into the block). When the thermostat opens water flows through the block and then out through the exhaust manifold. The circulation pump aids in moving the water through the block, thats all it does, its not a vaccum pump (4cyl VP don't even have them).<br /><br />The raw water pump is a vaccum pump and it is self priming but it must be wet or otherwise lubricated, a dry impeller will fry in seconds! A worn housing (scores, burrs, pits) will damage an impeller in seconds! Putting the impeller backwards will damage it in milliseconds!<br /><br />The bits from a broken impeller can get caught up in the system downstream from the pump and cause a blockage.<br /><br />The circulation pump is at the front of the motor just like a car, its driven of the alternator belt.<br /><br />Is the new (correct size) impeller damaged?<br /><br />Aldo

 

[calwldlif]

Re: volvo penta 170 overheating

Hello<br /> I also have a aq170 volvo.<br /><br />Have you attached a few feet of car heater hose<br />"7/8 dia" to the seawater pickup and the other end of hose in a 5 gallon bucket full of water?<br />The pump should draw the water freely and quite quickly. If doesn't...........<br />Could be worn "Cam" in pump houseing<br />Could be no keyway in impellar to shaft<br />Could be wrong impellar(too many teeth,thickness}<br />Could be wrong thickness gasket between pump and cover<br />Could be the rubber brass bushing o-ring seals that mount pipes to seawater pump.<br /><br /><br />If the pump draws normally, reconnect the sea strainer and<br />then disconnect the pickup hose from<br />the outdrive (right side of eng, stainless steel<br />pipe on outdrive}and attach a few feet of 7/8<br />"car heater hose" to the seawater side pipe<br />and place the open end of heater hose<br />in 5 gallon bucket full of water <br />If it does not draw water then check for air leaks along the pipeing to the water strainer, the strainer itself.<br />if it does draw the check the s-hose<br />and outdrive seals.<br />Hope this helps.<br /><br />By the way I am curious about the propellars<br /> you are using.<br />Are they alum or stainless?<br />What dia and pitch?<br />Right or left hand pitch?<br />What rpms can you get with them at wot?<br />Good luck and thanks<br /> Rick

 

[Dunaruna]

Re: volvo penta 170 overheating

Rick, Thats an excellent way to isolate different areas for testing, wish I'd thought of it <br /><br />Aldo

 

[tomcatdsl]

Re: volvo penta 170 overheating

Thanks Fellas, excellent suggestions. I'll give them a try tonight after work.<br /><br />r.e. the props, I don't honestly know, having just bought the boat and having never had it out of the water as yet. Sorry I can't respond to those questions.<br /><br />Thanks again for the help guys!<br /><br />Tom

 

[Peter J Fraser]

Re: volvo penta 170 overheating

Tom,<br />I also have VP 280 leg.<br />I did some research on the RWP on the internet.<br />My pump is manufactured by JOHNSON and I did have a price new but I dont recall it being that high.<br />The pumps are very rebuildable though even through the VP dealer here in NZ it cost me only about US$75.00 equivalent for a kit excluding the shaft.<br />The impellors will tolerat a fair degree of wear in the main housing, sure wear will shorten the life of the impellor but the condition off the cam plate is prob more important as that is when the maximum deflection of the imp. blades occurs.<br />You do need to have the gasket in place on the cover or the cover will increase the crush on the ends of the impellor and it will run a bit hotter.<br />Just give the impellor a light coating of rubber grease on the ends and a wipe around the inside of the housing before it is assenbled to prelube it for startup.<br />Dont give up, it will be something simple that is tripping you on this.<br /><br />Regards<br /><br /><br />Peter

 

[tomcatdsl]

Re: volvo penta 170 overheating

rubber grease? You mean like ky jelly? No, just kidding.....is there a brand or type that you recommend?

 

[Peter J Fraser]

Re: volvo penta 170 overheating

yeah that probably would work.<br />I cant really help with your local stores but any shop nearby that overhauls auto brake components or the like would have a supply of rubber grease.<br />Vaseline or petroleum jelly can also be used or even a little brake fluid.<br />Wont take much but you got to let that impellor slip freely until it gets water around it.<br /><br /><br />Peter