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aq145a exhaust manifold hot

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gryg1

Regular Contributor
Hi there.I have not been on for a long time and secking some help.I have new head on my aq145a,just got it started and have had river test and every thing went good.I went out to the sea and have noticed that the exhaust manifold is getting very hot on number one cylinder and also the heat exchanger is hot to,When pitting my had on the exhaust manifold on number 4 it seem ok,as i go to cylinder 3 its ok,when i go to cyl 2 & 1 they are very hot to touch.have been out for 2 hours and the water temp guage says below 1/2.I have a brand new manifold and have taken the raw water pump off to see if any thing was wrong with the impellor.all is ok.checked the water flow and checked the strainer and all is clear.Can anybody give me a hand at fixing the exhaust ploble heat.the water flows out of the leg good.plwase help
thanks
Stan
 
The raw water comes into the manifold from the heat exchanger at #4 port that probably explains why it stays cooler on that end. Sounds like you may have a restriction it the heat exchanger. Take and pour water in the strainer hole and fill up the heat exchanger and see how quickly it drains out with the engine not running? It should flow out fairly quickly. Start the engine with the strainer cap off and see if you get alot of bubbles in the water coming in the heat exchanger? Have you changed the fitting on the intermediate housing and is the hose in good condition. If it is not leaking on the pressure side you likely are sucking air on the suction side. Maybe get one of those large storage bins and put the lower unit in it and fill with water and pour a gallon of saltaway in there and run it for 1/2 hour or so that will clean the heat exchanger on the raw water side.
 
Which is the fitting you mention" the intermediate housing"
I kleened out the heat exchanger with air gun.
The funny thing is didnt have heating problems before.
Will try your sugestions and let you know
 
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Anothet quick questiom.would a restriction at the point where the water goes into the manifold cause the manifold and the heat exchanger to get hot.i figured it would make the manifold hot , but what about the heat exchanger.and would it effect the cooling of the engine water.
Thanks
Stan
.
 
yes yes and yes. There is alot of electrolysis that happens in the exhaust manifold and #4 exhaust port especially. To arrest it you can add a ground wire directly from battery neg to the back of the exhaust manifold. Look close at #4 port on the head for corrosion.
 
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you are talking about number 4 cylinder.i have a reconditioned head and a brand new manifold.i was thinking the fitting that goes under the manifol that comes from the oil cooler.if we have installed that with a lot of silicon i thought that some of the silicon might have flowed into the tube and resticting the flow into the exhaust manifold and is causing the overheating in the heat exchanger and exhaust manifold.would this restriction cause the overheating.
thanks
stan
 
First off never use silicone anywhere near a boat motor IMHO. Your problem could be a plugged oil cooler. Take the end caps off and rod out the tubes. If you must use a sealant use permatex aviation gasket maker and not silicone!
 
are the little holes i see are where the water flows through.so you do not think that the pipe going to the bottom of the exhaust manifold being restricked could be the problem
stan
 
Just follow the path the water flows from the heat exchanger through the oil cooler to the manifold and out the exhaust. There should be no restriction anywhere from the raw water pump to the exhaust.
 
hi,kim(i think)here is what ive done.
taken water pump off and checked impellor.all ok.good impellor,no slipping on the shaft or keyway.
putwater in strainer and poured some water in it ,water ran away ok.put hose in strainer and took of copper pipe going into bottom ofmanifold that comes from oil cooler,the water ran out of that pipe that goes into manifold great,full flow.
put hose into bottom of manifold to see it come out of the back of the manifold.its a big holeb,but the water seemed to come out pretty freely.
then put hose into the manifold that goes where the bellows goes into the leg and the water flowed out of the back ofbthe leg good.
examined the intermediate fitting and still looks like new.
i was the motor and leg out all the time so am very strick on maintance.
so all in all all water flow is pretty good i wouldvsay.
i was going to take the oil cooler off but see no point as the water between the strainer and afterbthe oil cooler was gussing out.
any further suggestions would be appreciated.orbanyone else got suggestions.
could it be the the new manifold is faulty and not allowing the correct volume.another thing i just thought of can you run the aq145a without oil cooler without any effect on the motor.i was thinking to put hose on and bypassing the oil coolervandvsee if that makes a difference,just a thought
 
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Adapt the oil cooler to the garden hose and give it a good blast of high pressure water both ways I really suspect it is causing the issue.
 
It will not hurt running without the oil cooler but I would like to add one to my motor if I ever find the parts for reasonable. If anyone has a AQ151 or 171 they are parting out?
 
My new manifold where the pipe goes from the oil cooler into the bottom of the manifold may be the problem.the hole which goes into the manifold is about 20mm but when looking inside it appears to have cast dags inside and the hole internally is only about 7mm elongated thereby restricking the flow into the manifold will post some pictures
 
Do you still have the old one to compare? I suppose it could be a casting flaw that may be a good thing for others to look at prior to installing a new manifold.
 
you should be able to see pictures now.got a replacement manifold and will put it on in the weekend and see what happens.do you know the torque setting for the exhaust manifold
thanks stan
or anybody
 
I could only find 15 ft lbs for the intake manifold bolts I imagine the exhaust should be the same. Personally I just cranked them down good and tight in a center out pattern in three steps. If the bolts are old and rusty 15 ft lbs may snap a couple. I use the german virgin value (goot and tight)
140-180 inch lbs is alot more accurate and less likely to snap them stay on the 140 side and see if it leaks.
 
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15 foot lbs is 180 inch lbs. Inch pounds is more accurate for lower torque values and with old rusty bolts your likely to snap them at 15 foot pounds of torque. I would wait for word from Ricardo or someone that has the proper torque value. I just use the good and tight formula. Then go back and give them another tug after the engine has fully cooled down.
 
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