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5.0GXI water infiltration

B

BK59

New member
I have purchased a 2005 Four Winns 288 w/ twin 5.0 GXI engines and Volvo DP-S outdrives. One of the engines has taken in salt water. My question is, do the DP-s outdrives have an exhaust flapper in the y pipe to stop back flow of sea water. The exhaust manifolds and risers have been replaced and show no sign of failure. They are fresh water cooled engines, so no raw water is running through the engine. The motor is seized up tight. I am not finding any flappers in the parts diagram. Any help would be appreciated. Thanks.
 
The Volvo SX drive used to have flappers but they deleted them, around 99 or so IIRC. I think they put some kind of grate at the top of the Y pipe to keep water from backing up the Y pipe at least that what some parts diagrams look like.
Did you actually remove the exhaust elbows to see if water was leaking down into the center section of the manifold?
There is a way without taking it all apart, on the Volvo elbows, there is a plug on the very top of it. This is for a temp sensor used on some engines. If you can get it out, you can snake an inspection camera down there and take a look. I do that on mine, here's a pic:
exhaust staboard side.jpg

if you can do this then you can rule out the exhaust leaking but it is still possible for water to back up the Y pipe if you stop too fast or the rear of the boat is heavily loaded. It would be a good idea to measure the height of the exhaust elbows above the boat's static water line.
Here's a pic of the OMC/Volvo style exhaust and you can see the fitting on the very top of the exhaust elbow...
4.3 with new exhaust system.png
 
I have the engine pulled and apart. The manifolds looked normal. all the cylinders had water in them and the rings are rusted to the cylinder walls.
I want to figure out what happened before I put a new motor in to avoid this happening again.
 
One motor took on water in all cylinders and the other didn't. Unless there is something different about how the cooling system is configured (which would not be normal) it has to be the exhaust manifolds, risers and elbows, or intake
 
with closed cooling the intake would have AF in it as well
That's kinda mysterious, why did one take on water but Mercury Marine had a nice service bulletin explaining causes including less common ones.
For example, and engine with a misfire could cause an abnormal amount of vacuum to build up in the exhaust system, that could actually pull water up the Y pipe.
Also, some Volvo engines especially later Vortec models, used a one way check valve screwed into the exhaust elbow, that was used to break the vacuum caused by valve overlap of the more aggressive cams used on the Vortec series. If these weren't present or not working, could be a possible cause. These were used more on the 4.3 V6 models, not sure if the V8s used them.
 
When I took the engine apart there was water in the oil but not milky, so it must have got in when engine was off. The bearings looked like they were nearly brand new. This was the original engine with around 450 hrs on it. It for sure came in from the exhaust somehow. The manifolds are fairly new according to the previous owner and look good. I will replace them anyway just to be safe.
 
What I’d do:
Before assembling the new exhaust check the sealing surfaces with a straight edge & feeler gauges, shouod be flat & level to less than .003” variation. Put the new parts together and follow Volvos instructions with respect to gasket sealer and torque specs Then prop them up level and connect a garden hose to the inlet fitting. Run the water for a while and look in the ports that mate up with the exhaust ports in the cyl head. They should be dry as a bone!
 
Finding leaks can be tricky. I would repeat the test and try turning the drive shaft & shifting it with the gear shift linkage.
Put soapy water on the propshaft seal and the seal for the shift bellcrank and watch for bubbles. Also use new fill and drain plug gaskets.
 
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