penta aqd40a over heating troubleshooting

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symondo

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Had my lesson on close quarter handling today which was cut short as the tempo' started to rise after an hour.

We turned it off at around 90 on the guage.

The weed filter was clean. Also took the lid off with the engine running and supply from the impeller seemed ok.

So what do I check now?

I let it cool down to almost cold before giving it another go and it rose up again.

So gave up at that.

Is there a pump for the coolant around the engine? Level of coolant was fine and no signs of any water /oil inside water or oil caps.

On the up side... I am happy I can now manouvre around a marina and moor up with a bit more confidence that I know what to expect and how to deal with it.
 
Last edited:
assuming all has been well recently on your low speed cruises, then I would check the impellor on the engine pump. Even if they have been recently changed they can fail.
 
kashurst said:
assuming all has been well recently on your low speed cruises, then I would check the impellor on the engine pump. Even if they have been recently changed they can fail.
Click to expand...

So there is another pump?

We had then services at the start of the season but I don't know where that would be located. I will have a look through the manual and see what I can find
 
Take a £20 quid note to Maplins and come back with an infre red thermometer gauge .
Check the actual temps on the thermostat cover ,compare both engines before arriving at your diagnosis

Time and temp work hardens the wires to to the gauges = change of resistance = false readings @ gauge s
 
Do you have the square heat exchanger box as per the very early AQD40A. ?
Would first take off the little brass plate on the front of the water pump underneath the water filters which is held on with six small screws and check that no blades are missing from the impeller ?
There is another impeller on the other end of water pump to move coolant around the engine block.
When you remove the radiator type pressure cap on the header tank are you losing coolant or is it actually filling up with extra water ?
In the very early 40a with the square heat exchanger , there is a brass matrix inside which allows the external sea water to cool the internal fresh water/anti freeze mix .This can sometimes split with age and allow the coolant to escape into the cooling sea water.
If you are lucky the heat exchanger may merely be clogged with crud and with care can be dismantled and cleaned.
Kit of bits is fairly cheap if you remember VP prices.
 
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oldgit said:
Do you have the square heat exchanger box as per the very early AQD40A. ?
Would first take off the little brass plate on the front of the water pump underneath the water filters which is held on with six small screws and check that no blades are missing from the impeller ?
There is another impeller on the other end of water pump to move coolant around the engine block.
When you remove the radiator type pressure cap on the header tank are you losing coolant or is it actually filling up with extra water ?
In the very early 40a with the square heat exchanger , there is a brass matrix inside which allows the external sea water to cool the internal fresh water/anti freeze mix .This can sometimes split with age and allow the coolant to escape into the cooling sea water.
If you are lucky the heat exchanger may merely be clogged with crud and with care can be dismantled and cleaned.
Kit of bits is fairly cheap if you remember VP prices.
Click to expand...

The matrix inside i assume would be the thin pipe or more you can just about see and feel inside the cap?

We checked the impellor for the sea water, that was ok. Im sure its the square heat exchanger, ive got a photo somewhere.
I suspect it could be this second impellor as im not entirely convinced it was replaced at the last service looking at the invoices as by simple maths, that'd be 4 new impellors, not 2.
 
There are two separate pumps
A gear driven salt water pump of the "jabsco " type which has a rubber flexible impeller which is subject to anual checks and or replacement which circulates water through the oil cooler heat exchanger and out through the exhaust and is liable to breakup if denied water.
The is also a belt driven fresh water which circulates a mixture of fresh water and anti freeze round the engine block and cyl head this is a sealed system and has a tank with a pressurised cap the impeller is steel and not subject to the same damage as the sea water pump
Both pumps have a central shaft and seal which can leak usually through a tell tale hole
 
Agree with portifino. Laser temp guns are a must.

If you can also read the exit water from the engine as it enters the exhaust when the overheat occurs you might be able to narrow it down.

2 cooling circuits- 1 raw water, 1 fresh(coolant). If raw water circuit getting too hot it will not be able to take heat away from fresh water circuit. Best to determine which is getting hot first.


http://www.flushsok.co.uk
 
tribblehunter said:
Agree with portifino. Laser temp guns are a must.

If you can also read the exit water from the engine as it enters the exhaust when the overheat occurs you might be able to narrow it down.

2 cooling circuits- 1 raw water, 1 fresh(coolant). If raw water circuit getting too hot it will not be able to take heat away from fresh water circuit. Best to determine which is getting hot first.


http://www.flushsok.co.uk
Click to expand...

logical n methodical - sounds like a plan - caught me out a little over the weekend but didnt have much time to investigate properly.

If i raise the outdrive to the top position would i be able to visibly see if water is exiting the raw output? from what i remember the exhaust is above the prop on the 280 legs.


Also i had a chat with the guy who did our servicing this morning, hes also suggested checking the thermostat. i assume if i was to put said thermostat in a bowl/pan and put hot water in i should see if it is working or not?
 
DO NOT lift the leg all the way up with engine running. The Universal joint may get damaged. (When engine running the UJ is turning all the time whether in gear or not)

By the exit water I mean the raw water leaving the engine BEFORE it mixes with the exhaust. Sorry i didn't make that clear.

If you locate the small elbow on the larger exhaust elbow this is where the water exits the engine on a typical installation. Sbd side of your engine to the rear.

Read this temperature either by hand or preferably with laser gun. Must be read at full power. Please be aware this is dangerous if you do not prepare things properly as you will possibly be leaning over a hot engine with the vessel bouncing around. If you have access from above the engine exhaust elbow without being in the engine room it would be better.

Typical temperature is below 50 degrees celsius. THIS IS ONLY A GUIDE THOUGH as all engines are different.

Your original reported problem appears to be what I term 'A creeping overheat' where the temperature of the engine crawls up over time.


http://www.flushsok.co.uk
 
This is intended to be helpful; from the owner's manual for 41B: Normal operating temperature 75 - 90 C, stats fully open 81 - 94 C.

ATB,


John G
 
For lower loads issues you can put your hand on the exhaust elbow or the seawater pump housing to understand if the seawater flow is the issue or not. The pump housing should be "cold" and the exhaust elbow a bit warmer but still ok for a quick and light touch.
I just had my circulation pump break and the difference to typical issues with the raw water flow (of which I have had many) is that it's much quicker to overheat, It's almost instantaneous if you put some load on the engine. To confirm it was the circulation pump I removed the thermostats, put the housing back and then started the engine checking if there was any flow of coolant.
 
Just re read original post.

Teach me to skim posts too quickly! 'Overheat happening at low speed.'. :redface-new:

My earlier comments may not be valid in this situation......

Now hanging head in embarrassment.

Agree with stats and circ pump. Still advise use of laser temp gun. Take temps of stat housing above and below stat, coolant in and out of heat exchanger and raw water at water pump and at exhaust elbow. There will be some indication from those where the problem lies.

(Note to self...... Don't skim posts!)
 
Thanks!

I had a chat with the giys who did our service today as well. Not sure when i'll get back down but will check out flow as best i can but has also been suggested to locate and check the thermostat, even swap them over from each engine to rule it out.

Im going to take a mate whos handy with the spanners as well as hes keen to take a look n see what the boating thing is all about
 
I hate to say it, but overheating is quite a common issue with the 40s as the cooling system is marginal at best. I have 40As, but with the B exchanger on them (tube, not plate which you have). The usual problem I experience is blocking of the oil cooler - it's the first thing in the raw water circuit and the problem will show itself at higher revs. I usually have to clean (gently rod with a coat hanger) the oil coolers out on both engines every 4-5 seasons.

Of course, it could be other things - or a combination of several things - the suggestions you have from others all seem sensible, but don't overlook others such as;

- the impeller having failed (i.e. the rubber spinning on its hub)
- blocked intake filter
- blocked exhaust elbow
- stuck thermostat(s) - verify by removing the thermostat
 
dragoon said:
I hate to say it, but overheating is quite a common issue with the 40s as the cooling system is marginal at best. I have 40As, but with the B exchanger on them (tube, not plate which you have). The usual problem I experience is blocking of the oil cooler - it's the first thing in the raw water circuit and the problem will show itself at higher revs. I usually have to clean (gently rod with a coat hanger) the oil coolers out on both engines every 4-5 seasons.

Of course, it could be other things - or a combination of several things - the suggestions you have from others all seem sensible, but don't overlook others such as;

- the impeller having failed (i.e. the rubber spinning on its hub)
- blocked intake filter
- blocked exhaust elbow
- stuck thermostat(s) - verify by removing the thermostat
Click to expand...

Ive found the diagrams of the thermostat and where its housed - i assume the engine will run ok with the thermostat removed provided this could be the issue.
 
One of my TAMD40b's (Same engine, shaft drive) was overheating last year, only at higher revs, and whilst nothing was apparently wrong, I removed the new impellor, found nothing wrong, so refitted it.

That cured it!?
 
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