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Overheating AD41

nikita33

New member
"I have owned this boat for ye

"I have owned this boat for years and tried all things possible to get it to not overheat over 3100 rpm's it's far better today after all that has been done but still after a while at 3500 it will start to overheat (both alarm and temp proves it). Just ex from my long list is: Cleaned heat exchanger, cleaned oil exchanger, check all connections from water up to pump (incl stern drive and connections), rebuilt raw water pump, checked internal water pump, changed thermostats, checked all tubing for internal obstructions, cleaned exhaust elbow. Please is there anything I have missed I think I have tried it all...Are there anyway to check that I get enough water through raw water system like measure rpm with liters going out..or..? Please this is driving me cracy I need moore sugestions.."
 
Unfortunately yes intercooler

Unfortunately yes intercooler also cleaned also maybe I should add that I don't loose any fresh water from the internal system at all so no leaks and water looks fine no oil leaks or so.
 
"May I suggest You get hold of

"May I suggest You get hold of a heat gun and try to find out where/how the heat builds up in the raw water circuit from inlet to when it enters the exhaust outlet.
How is the color of the exhaust? A bit difficult when drive, but Volvo's have a black smoking tendency particularly at acc and just after the turbo gives full power and opens the pump. If it runs lean, that might cause a problem. What kind of coolant are You using and have been using?
Perhaps a good round of cooling system cleaner to clean out block might help, and the use of non-cavitating coolant?
Do You have any hot-water heaters etc hooked into the system?"
 
"Thanks a lot for assisting Mo

"Thanks a lot for assisting Morten, do you think an IR temp mesure instrument will work..could I then messure ex inside temp in thermostat housing ? Or will ext temp on housing an piping be enough ? If there would be an obstruction in ex a pipe would I see that temp builds up right after the obstruction ?
Exhaust color is very hard to say off course when starting there are smoke but later on I don't think it's more than other ex of this engines I've seen.
Type of coolant, well in Swedish it's named Glykol I guess you know Norvegian from start right..I have a mixture of 40% glykol and 60% water changed this year. Maybe I should try cleaning system and non-cavitating coolant.
Also I have a heater but there is no differense if I block the channels to it I have tried that..
I guess I will buy a IR temp measure instrument then they are quite cheap and could probably help me a lot here."
 
"I had a similar problem with

"I had a similar problem with my TAMD41A engine, the problem was after rebuilding the raw water pump the wrong size cam was reused therefore increasing the space between the impeller & the pump wall & not making a tight fit for the impeller to pump enough water over 3000rpm. Recheck your raw water pump & compare the different size cams that come with the rebuild kits."
 
"Thanks but also this I think

"Thanks but also this I think is ok cause I baught new original cam and pump, but still I will check if there are different sices."
 
"Normally this engine should h

"Normally this engine should have about 25% over-capacity in the raw water cooling circuit. This will give the effect that raw water into heat-exchanger will be not much more than 10C lower than raw water out. However it depends somewhat of which of the AD's You have: A,B..... Quite some parts have been modified/replaced on the different models.
Some of the more common problems in the system are except for wear in the raw water pump, wrongly installed heat-exchanger element ( rear/front seal not properly sealing and coolant sneaks through, cavitation wear on the circulation pump impeller. If no difference in blocked or open circuit to the hot water heater, the circulation pump is probably not the culprit. I go more in direction of heat transfer between raw and fresh water circuit, but an IR reader might tell You more about it. If raw water out from heat exchanger passes 45- 50C, You have a raw water problem. I guess the sea-water temp in Your area is about 15-18C."
 
"I have model A and it runns g

"I have model A and it runns great besides this heating problem. I have chnaged the T formed rubber sealings in the back but are there similar in front..? I can't see any in marinepartseuropes dravings. Perfect anyhow with these readings you are refering to so if I have more than 30 after the heat -exch then I most likely have an issue there or before...I will by tool and start meassure, I will have to run full trottle right so it will start to overheat..? Or could I see this already at lover revs ? Thanks a lot for helping also at Volvo here in sweden they have run out of things to check..."
 
"You may start at lower rpm&#3

"You may start at lower rpm's and take readings at every 3-400 increase until the problem comes. You might probably notice symptoms earlier than when overheat starts. If raw water circuit does not make a 'jump' then You know You have an internal circulation problem. If raw water circuit climbs equal to internal temp, most likely a raw water problem.
Remember to check that the block itself has even temp, and not some odd hot-spots.
Do You have an oil-temp instrument installed?"
 
Sorry now I don't get it..

Sorry now I don't get it..not make a jump=int circulation problem but that's the same as climbs equal which should mean raw water could you please specify maybe a typo or ? Unfortunately I don't have oil temp only pressure.
 
"The engine temp will probably

"The engine temp will probably go up as You apply load. At some point it will probably peak and You get the overheat situation. If the raw water temp peaks (jumps) with the engine temp, You have a raw water problem."
 
"So now I have baught an IR gu

"So now I have baught an IR gun, tested it on my car just minutes ago works fine in to heat exch one temp and apr 10C out just internal system there but very easy readouts. I will post again when I have had time to measure."
 
I am going through the same is

I am going through the same issue at this point.The temp jumped from 175-210. I took my boat in to a shop and they said the problem was a leaking head gasket.So I ran my boat at my home port and the boat ran at 201 degrees. I called the mechanic/Owner an he said my boat should run at 195 -201 at 3000 rpms. I said BS my boat always ran at 175-180 for 6 years. By the way I have a AD41DP.So I was told from numerous people that the Outdrive has a Bushing that wears out and Air sucks in there and caused the engine to overheat.That is common with the ad41. SO we checks that but that was also fine. Well the only thing left to do after checking the entire cooling system was the thermostats. The AD41 has 2 1 with a airvent and 1 without. Well.. 5200 dollars and without the mechanic checking the thermostats that was the problem. We ran the boat without the thermostats and the boat ran at 165 degrees. With the new thermo stats the boat ran at 175 -180.Case resolved but Im out 5200 dollars with a reprible boat shop getting one over on a customer.
 
Ok I have changed my thermosta

Ok I have changed my thermostats but I recall them both looked exactly the same so you mean one of them should be with airvent and one without...I will have to check that.
Also this weekend I did some testing with my IR gun seams like I have some problems with heat exch cause Morten advised out temp from heat exch to exhaust elbow should be apr 10C over raw water intake. Mine was 45-50 after just a short run I would asume after longer time I probably have over 50C in out water temp to hot acording to Morten (raw water temp was 18C). What I don't understand is where the front sealing in heat exch is lokated (the ones in the back I have changed). Would be great if you could advise Morten ?
 
"No front dividing seal, only

"No front dividing seal, only rear, my 'mistake'.
From Your readings it seems that You have a raw water problem as raw water out from heat-exchanger seems to climb up to close to engine temp! That means a capacity problems caused by restraint in drive/hoses/filter (before heat exchanger), pump capacity or blockage in water out after heat-exchanger. Have You checked that the 'big' drain/water inlet at the bottom of the drive is open and not blocked in any way? (not the side-inlet, but check them anyway)."
 
"Thanks a lot Morten, but yes

"Thanks a lot Morten, but yes I have cleaned the whole inlet part in the drive also took drive apart and changed sealing just to eliminate that problem also tested the whole part before raw water pump by sticky tejping the inlets on drive and preassurised from raw water pump no leaks at all. One thing though I have not changed is the closable valve placed on the inside of boat connecting to the drive hose but it's checked(no leaks) and it's in open position."
 
On later versions that valve h

On later versions that valve has been replaced (eliminated). Would have checked if the new one (no shut off) fits Your set-up.
 
"Thanks a lot for your great h

"Thanks a lot for your great help Morten, I will try to change the valve this winter. One other thing...this could not be caused by bad filler casp spring so I don't get enough pressure in the fresh water system, just saw a note about someone who had bad spring but lost water..But I should not think I little lower pressure could cause this or what do you think ?"
 
"I saw the posting, but did no

"I saw the posting, but did not comment.
Low spring pressure will not affect the situation like You are describing. It will release the water to the expansion tank, and might make the coolant fluid cavitate (create air-bobbles) that will eat the circulation pump impeller. I do not think he lost coolant due to the spring, but a faulty gasket in the cap. It is a kind of double sealing system. The spring seals off and builds pressure, the cap seal prevents water from leaking out if spring gets compressed and directs the coolant to the expansion tank.
Don't forget to 'report' back when You get the 'valve' changed/inspected."
 
I will report back but unfortu

I will report back but unfortunately that will be in May 2009...a long winter before that. I might also try to take apart the piping that I have not yet checked during winter and make 100% sure I have no obstructions. Also I am considering to once again clean the heat exchanger last time it was done by a company and maybe if they did a bad job who knows... as you know I'm running out of options...
 
"I would not have bothered wit

"I would not have bothered with the exchangers.
Enjoy Your winter and snow-shuffling, I will try to survive in the constant +30C."
 
"Hi again, just a question to

"Hi again, just a question to Morten again...after reading all this again a noticed that you wrote out water 'passes 45-50' but you meant if out water is=45-50 then I have a raw water problem right. Cause I have like 30 degrees raise I should have like 10 or something..Just want to be sure before I start dismantle the engine again (she is up on land again for a long winter here in Sweden..)"
 
"The temp on the 'out'

"The temp on the 'out' water from heat exchanger should not be hotter than You may hold onto the tube/hose coming out, which will be about that temp range max. I little pity You did not run Your test with heat gun until alarm went off to get a max reading of Your 'out' temp.
Please give a feed back on Your progress and when You have pulled down the shut-off valve in the transom. Had a set of AQAD31's in a Finnspeed 850 (x police boat) many years back, and replaced both valves with straight-through 'custom made'."
 
The problem is that alarm does

The problem is that alarm does not goes off it's just starts to sound just a little bit and always when the sea water temp is 18-19 and after longer drive when engine is real hot..But yes you are correct I should drove it a bit longer to see how much the out water climbs. So if I read this right it could still be ok if I have 50 deegres but not much more like 60 or above. Did you have exactly same problem with the Finnspeed and did the replacement of the shut-offs cure the problem ?
 
"I used the boat year around,

"I used the boat year around, even in ice!!
Was running a rescue/salvage service and during winter time when the police was safely stored in a heated hall, they called on me.
Tried to close the valves once, handle broke off with valve half closed - out they went!
Noticed afterwords that my exhaust raiser temp dropped quite a bit at full load. (special installed to keep a better track of cooling)."
 
"I had similar problem just af

"I had similar problem just after I bought my boat. I know this may sound stupid but the previous owner had used exhaust rubber pipe on the raw water intake. So when the suction increased as the engine revved higher the pipe started to collapse inward, therefore starving the motor. Certainly solved my problems."
 
"Actually this pipe is on my &

"Actually this pipe is on my 'to do list' this winter. Probably yours had a intake through hull right? Mine is at the drive. Still this short pipe only between engine and drive unit has a pretty sharp bend might it be that this bend together with increased under pressure at higher revs might squise it together even moore. For sure I will change this peace of tubing together with the closable valve this winter.
Great tips thanks a lot Paddy, now I also know that this peace of tubing is very important."
 
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