450 Dancer/3126 Cat Exhaust Question

[mikey18605]

Have a 98 450 Dancer that performs correctly in terms of no overtemp and obtains 2800RPM. My question is about the exhaust system. One side at idle spits water and exhaust out the side above the water outlet like the waterlift muffler on the generator. The other side pours out less water with the exhaust. This side also requires more RPM to cause the exhaust to use the below water outlet. Both engines pump about 4 gal. in 10 seconds at idle. Have new impellers. Both exhaust systems are near identical, all hoses OK.

This suggests one of the buypass mufflers has a problem. The question is which one?

How do other 450 Dancer/3126Cat boats act?

 

[fwebster]

What you are experiencing is normal for a 450DA.

Look at your exhaust systems again........both sides make 2 90 degree turns before going to the muffler, but the stbd side has longer runs since the exhaust must cross the width of the engine. The port side has 2 bends close together. There may be some difference in the mufflers as well. While this might not look like much, it does make a difference in the amount of water expelled above the water line.

With the under water exhaust fitting used on the 450, the small exhaust port above the waterline is just an over flow. The water that comes out there does so because there is back pressure at the underwater fitting. You have determined that the rate of flow is the same....i.e., 4 gal in 10 seconds.......so the difference in visible output from the overflow just means one side has a little more back pressure than the other. Idle up both engines a couple of hundred rpm and the weak side should get enough flow so that the sides look the same because the added water at a little higher rpm is more than the underwater fitting can accommodate.

Check to see if you are picking up barnacles in the underwater fitting since they will increase back pressure.

Caterpillar significantly over specifies cooling systems and it takes a lot to make one overheat, but that is the sign to look for if you have flow problems. It will start with gradually increasing temps at high rpms under load. The engines should run at 185 to 194 degrees and when the temp creeps up over 200, its time to figure out what's up.

You mentioned muffler problems, but the mufflers Sea Ray uses are very good and seldom cause trouble. If there is a muffler problem, it will be a baffle broken loose inside the muffler. The sound is easily identifiable..........at idle it will sound like a monkey inside the muffler trying to brake out with a hammer....one of those noises where everyone on the dock has to run up to tell you that bad and evil things are going on and your boat is going to self destruct immediately. At that point you can tell them its your muffler monkey trying to escape.

Enjoy your 45 ......they are one of the best Sea Ray ever produced.

 

[mikey18605]

Frank:

Thanks for the input. One further fact is that at 1000 RPM at the dock, the port side is exausting through the bottom through hull, while the STB side is not. The STB side is also the one with much less water flow with no spitting, while the Port has more water flow and spits like the generator water lift muffler.What does this info tell you?

Mike in Florida.

 

[fwebster]

Unfortunately, it tells me that your boat and mine are just the opposite.

My sea water pumps are new and the bottom is clean of barnacels so I'm pretty sure I don't have a cooling problem.

Both heat exchangers are in line with the sea water pump and flow. Have you cleaned them recently? The transmission oil cooler is particularly bad to catch grass that is so small it passes the strainer and primary heat echanger. They are easy to check, just pull a hose off the inlet end and take a look.