Uneven water flow on a 400 Sundancer with 3116

[Mhansson]

Hoping someone can point me in the right direction. I have noticed that at idle in the marina that the water flowing from the above water line outlets is appreciably different between sides. The port side has a small amount of water, while the starboard side has a good, high volume flow. When I raise the idle to over 1000 RPM I see similar indications of exhaust flow from under the boat. There is no sign of overheating and the boat ran just fine on an 8 hour trip. I have had a cat mechanic look at the boat and he is questioning a blockage in the exhaust splitter but says not to worry, as long as there is no sign of overheating. I have inspected the port side impeller and it is fine.

I not a big fan of the"don't worry" method of maintenance and before I start tearing things apart, I figured I would see if anyone else has any suggestion.

Thanks

 

[fwebster]

The plumbing to get the cooling water out of the boat is different on the port side than on the stbd......longer runs and more turns. That means the same volume but pressure losses and lower velocity of water flow, assuming the impellers are equally new and there are no heat exchanger blockages. Now, the "above the water line outlets" outlets are really over flows for the underwater exhaust outlets. You only see water from the over flow when there is more exiting than the underwater outlet can handle. Therefore, given that there are plumbing differences causing different velocities and pressures in the exhaust flow, it is entirely normal to see more water flowing out of one side at idle than out of the other. My advice is to not spend several thousand $$ tearing apart a functioning system in search of an answer. I agree with your mechanic......unless you have have overheating or signs of rising temps as rpm's increase, then "Don't fix what isn't broken".

 

[Mhansson]

Thanks for the help Frank. Now I can spend the money on something else!

 

[peterkvs]

If you have a IR temperature measuring gun you could look at the temps of the water tubing, exhaust tubing, etc and compare sides. That is only if you need a warmer fuzzier feeling than you have.

Pete

 

[THJeff]

I have the same situation and my mechanic gave the same advice. I'm glad to hear Frank agrees.

 

[Turtlesboat]

My port goes "woosh woosh" and starboard goes "wooooooooooshhhhhhhh"

 

[ImpulseIII]

I love those technical terms.

 

[LMBoat]

Have you verified idle rpm with a photo tach? Mine did the same thing. Turned out the RPM's were a little differencnt. Trued them up, all is even now.

 

[Boat Guy]

How do you "true up" idle rpm and do you want to? I put digital tachs on my boat and can see they are not exact at idle.

 

[fwebster]

It is best done with a non-contact digital photo tach while standing between the engines where you can see both harmonic balancers. Unless you know what you are doing, stick with adjusting only the idle stop screws on the fuel pump.

Also, keep in mind that the governor is sensitive to oil temperature so the idle should only be set when the engines are at operating temperature.

 

[Mhansson]

Mine goes more like "spit, spit"........."whoosh". Is there a technical post on the idle stop screw adjustment?