AQD40a raw water pump

[eddieperkins]

I have had an ongoing overheat problem on my AQD40a's on 280 legs and am looking for the solution, I have gone through the systems several times and thought I had a fix but it seems that no sooner have I got one engine working right the other starts overheating. I think it is just that the cooling system on these engines is just not up to the job. I am now thinking it is time to upgrade the raw water pumps and take cooling water through hull fittings instead of through the legs. So the question is a. is there a raw water pump upgrade kit or has anyone any recommendations and b. can anyone see any problems with not taking coolant through the legs. Boat is a Sealine 305, 30 foot flybridge. Regards, Eddie

 

[rich]

Eddie, I solved my over heating problem, by taking off the jabsco pumps, reversing the face plate, and grinding the surface of the pump body on emery paper laid on glass, the difference in water volume was amazing

 

[eddieperkins]

Rich, I have had both pumps overhauled including having them resurfaced on the inside face and skimmed on the front, with new face plates and impellars. Was OK for a while but I am still getting overheating.

 

[TRH]

Hi I had the same problem,My cure was to clean out the ports in the Exhaust elbow,this made a big improvement.

 

[dalex]

Hi,
I noticed that very little water was being sucked up into the Vetus strainers. My approach was a rebuild kit from Volvo (ouch) which doesn't have ALL the bits you need /forums/images/graemlins/frown.gif
There are a lot of things which can cause overheating.
Blockage or other obstruction in saltwater intake (barnacle shell? - little gits!)
Freshwater thermostat not opening
Air leak on suction pipe from the drive legs
Slack or slipping water pump drive belts
Blocked or scaled-up heat exchanger etc
Engine working harder than it should due to something round or between the props and the leg,
leaking or blown head gasket
As has been said, the impeller face must be flat to get a decent seal. When you took the old one out, did the old impeller have all it's blades? Is there any sign of water dripping from the pump?
The pump has to suck water a long way up a pipe, and any air leak would have dire consequences for keeping primed.
Best of luck with it.
(another 305 owner)

 

[Margem]

Eddie this must be driving you mad by now, I have had similar twice, know your pumps were overhauled buy did they check the back/wear plate, it was this on two boats i had, cured it after months of f.......ying aroud try all known to man!

 

[ipw]

I had a problem , ended up taking exchangers off and cleaning , turned out to be a broken vane on impellor. I,m machining up the offending pump fitting new bearings and seals , chroming up the shaft as it has been damaged through running dry. The inlet water fitting on the leg is also prone for corroding.I ordered up a raw filter mail order and they came too big so the 40b(165hp) pump will probably fit as it is the same engine but aftercooled , any more info give us a e mail.

 

[eddieperkins]

Hi, The engine that is currently giving me the problems (I'd swear they are taking it in turn to play up and having a giggle at me) was out of the boat last winter and had a full rebulid back to original spec by a very good engineer. Pretty much all moving parts replaced for new and the leg was serviced and refitted with awareness of overheating issues. Water pump was skimmed internally (no wear plate on this pump) and faced off with overhaul kit fitted and new heat exchanger matrix fitted (ouch, circa £800!). Was initially ok but is playing up again. I have not yet had a chance to investigate this one yet but there is definatly not sufficient flow through the pump. May just be the impeller but it has only been in there half a season with not enough use as I was refitting my kitchen. I am just at the point where I think there is a general flaw in the cooling system engineering and a modification is the best way to go now. So has anyone converted to larger pump supplied via skin fitting rather than the leg. Another factor that may be relevent is that I am on the Broads and may be sucking mud up through the leg on occasions which soon bu**ers up a pump, but again, I have not yet stripped it down and this is only a theory at the moment.
Regards,
Eddie

 

[dragoon]

Hi Eddie,
It sounds like you may have a restriction if you're sure that there is not enough flow. I have TAMD40b's which are very similar. I would look at the oil cooler and the exhaust elbow (the latter blocks up with rust and can be poked out with a coat hanger). You may be able to "back flush" the system from the connection at the elbow. This has helped me in the past and may remove restrictions in the coolers/pipes.

One other thing (although this may only be the "b" and not the "a" series) - there is a rubber helmet on the aft end of the exchanger - if this doesn't seal correctly flow through the exchanger can bypass the exchanger completely (it has a pair of rubber lips running the diameter across the inside of the helmet which separate the in flow from the out). I've heard of this causing cooling issues. As I say, this may only be for the "b" as the exchangers are different.

Good luck.

Cheers,
Paul

 

[oldgit]

Hi Eddie.Have exactly the same set up in my boat.40A with 280 outdrives but prob a bit older being around 1982.The boat sits on a mud berth.My system is still working OK.The only problems arising in the cooling dept being a split heat exchanger(fixed by my local car rad co. for 20 quid and the the need to prime the raw water sytem if boat was not started for a week or two.This was sorted by a new impellor as the old one had developed a pronounced "set" in the vanes.As to those pumps both the back plates on my raw pumps are fairly heavily scored but this has not obviously affected the water flow or my water temps.Does this overheat happen at low or high revs.Have you removed thermostats.Are the sender units the correct units to match the gauges.When did it first start.How about hiring a thermal infra red thingy and aim it at the engine block find out where the blockage is.

 

[eddieperkins]

Hi guys, Thanks for the replies. The poor flow is evident from the lack off pressure in the rubber hose from the oil cooler to the heat exchanger and lack of flow when the hose is removed, so the problem is probably with the pump. Restriction from damaged impeller vane causing blockage unlikely as the pump flows into the filter before going off to the oil cooler. Also blocked exhaust as full rebuild using volvo parts eliminates all the other suggestions. May be blockage from leg end, may even have been caused by bag around leg causing impeller damage, but I have not been able to check yet. May be tommorow if the promised snow does not put a blight on working on the boat. It just seems that the set up is so barely adequate that any slight malfunction leads to overheating and it is getting me down. I am on the broads and most of the time travel at river speeds and all is well, but it seems every time I find myself in a position to open her up one engine is fine and the other overheats. I have not been able to get up and running for years now. I now believe that in order to be able to use to boat to its full potential (as and when I feel the need) I need to go back to the drawing board and make changes to the cooling system to eliminate all the leg/planning reated problems and also upgrade the pumps to ensure good flow thorugh the heat exchangers. Just not sure if this is an option or not.

 

[dalex]

<quote>How about hiring a thermal infra red thingy and aim it at the engine block find out where the blockage is.<unquote>

Brilliant! I was jut looking for a damn good reason for getting one of those heat sensor gun laser things from Maplins... Capital suggestion!

 

[Greg2]

I haven't had the same engines (so this may not be relevant) but for what it's worth I did have overheat problems when running at speed at sea last season, which I managed to have sorted.

As Olgit has suggested a laser/infra-red themometer is a good investment. Not too expensive (from Maplins) amd when pointed at the best spot (identified by our marine engineer) I found that the engine wasn't running as hot as the guage suggested, albiet it was higher than it should have been.

It was, however, above what it should be and having spent a very frought day hanging upside down like a fruit bat in the engine bay, going thorough the entire cooling system, I had the after-cooler removed and found it was blocked with foliage as well as being 'furred' up with limescale. Had the limescale removed and problem solved.

We are on the Broads too and for what it is worth the only time that I have knowingly sucked up mud is when we took an unscheduled detour onto a mudbank on Breydon. Usually we get very little in the strainers apart from the odd bit of foliage (the foliage blocking the system was very unusual and was down to high levels of debris in the marina due to expansion works).

 

[oldgit]

Eddie,just a thought,but the impellor which failed on my on my pump was a version which had more vanes on it than the standard Jabsco/jabsco copy.It had only been in the pump for about six months.And something else....when you go to boat and remove the filter lid,is there any water remaining in the pot or has it all drained away.The impellor should give tight enough fit in pump housing to prevent water draing back past it and emptying filter pot and also lid must give air tight seal.The inner dinner plate lid thing with rubber ring seal under lid should be [--word removed--] to get out and mine needs knife blade or summat to break vacuum in order to remove it to inspect filter mesh.Also wonder if water leaves filter and exits cooling sytsem via engine block as much by gravity as pump pressure.So flow might feel bit weedy if using fingers to detect any pressure in pipe.

 

[eddieperkins]

Thanks for the imput guys, still have not had a look, will report back when I have more info. I have had a reply from another forum, (can I say boatdiesel.com here??) which suggests I can upgrade to the 40b set up (ouch many bucks) and that intake via hull is ok, just trying to find out if I can blank off the leg pick up also. Fred, the vacuum in the strainer is usually ok but after the overheat the strainer was empty which leads me to suspect a faulty impeller is waiting to be found. Also interestingly enough I have had the same failure with a jabsco replacement with more vanes than the Volvo supplied impellor. Greg, I think the mud suck up issue is more likely with outdrives as they work fairly close to the bottom sometimes and must pick up more I would have thought.
Regards,
Eddie