AQ125 exhaust manifold overheat issue

[dhjeeps87]

hello good people, I have a AQ125 I'm chasing heat issues with and today upon removal of ex manifold, and cleaning i re installed and noticed im getting exhaust pressure out the water feed tube that dumps into the manifold. Is this normal? I also removed the heat exchanger to clean it. Just cranked it up for a second to check exhaust for leaks.

 

[alldodge]

getting exhaust pressure out the water feed tube that dumps into the manifold.

Howdy
No that should not happen and you have a head gasket failure would be my guess

Do a compression test

 

[ripjmk]

I'm not familiar with AQ125 but just guessing the exhaust is raw water cooled same as others. So, also just guessing from your brief description, if you are talking about a few second run of the engine while the heat exchanger is still off the engine and the water feed hose to the manifold hanging loose. Then yes exhaust gas would come out of the hose as there would be no water flow to stop it!

 

[dhjeeps87]

Thanks for the help! I did run compression check when I bought it and all cyl where at 180 psi. I was actually pretty surprised by that. As far as the manifold goes I have ordered a new one anyways theres was crud in the back exit ports even after I cleaned it so that will be one less thing to worry about causing it to run hot.

 

[alldodge]

all cyl where at 180 psi.

Ya need a new gauge or there is liquid in the cylinders. Compression should be around 150 psi

https://www.boatinfo.no/lib/volvo/manuals/aq125_145_ab.html#/64

 

[dhjeeps87]

I did crank it longer than usual. Either way there's def no compression issue i can find. Or headgasket leaks nothing is mixing or losing coolant.

 

[kenny nunez]

If you still have a heating problem after replacing the manifold try connecting a garden hose to the water supply pipe on the inner transom to back flow the incoming water supply. Where the water enters the lower gear housing try to block it with your hands to see if the “O” ring that seals the lower gear housing to the suspension fork sprays out water and also look at the water hose on the transom shield.
If the “O”ring is leaking then air is being drawn in when the boat is on plane. This is an easy repair just be sure to get the genuine seals from Volvo.

 

[dhjeeps87]

Thank you for that info I was wondering if there where any points air could enter below the aluminum water inlet on the lower unit. Is this due to the unit turning left and right and the inlet neck staying centered and not rotating with the lower unit?

 

[kenny nunez]

The “O” ring is located in a wear area and also over time gets compressed. The aluminum hose nipple has a gasket style seal that also is a wear item. Most times the aluminum is corroded away and the hose is just barely on. Also easy to replace with a shortened fractional Allen wrench. Volvo got it right the first time as far as simplicity of repair and with SAE and not metric PITA hardware,

 

[dhjeeps87]

I've got the aluminum hose neck and gasket on order. I will have to further investigate and find where the o ring is you're talking about. I think i have an idea, but not positive.

 

[kenny nunez]

If the “O”ring below the suspension fork needs to be replaced all you will need is some allen wrenches for most of the bolts and remove the shift linkage cover. But first try blocking the intake grill with your hands to see if the one below the suspension fork is leaking when back flowing the water intake, maybe it is still sealed.

 

[dhjeeps87]

I FINALLY.... figured it out. The tube that is inside the water pickup has some play side to side. I remedied it by placing an o ring around the outside then putting the water housing gasket on top of that, then tightened the new housing up. Ran water down the tube after I taped the water intake closed and no more leaks even when I try to wiggle the outdrive and get a little movement. Lake tested for hours and never got above 190.