Proper flushing procedure?

[waternutt]

I recently had to replace the exhaust manifold on one of my engines due to a water outlet nipple being completely corroded and falling off. I do use it in saltwater, but I am the original owner of the boat and flushed the exhaust after every outing. I am beginning to wonder if my flushing procedure is incorrect or something else I am missing.

My flushing procedure seems similar to most on here: connect hose, start engine, turn on water, turn off water, turn off engine. I typically flush for no more than 2 minutes (1 min with freshwater, 1 min with saltaway) with the engine at idle. After the water is off, I will finish up by giving the engine a couple quick revs to get out any last water.

Looking in the Rotax operators and service manuals, they both mention running the engine about 20 seconds at a fast idle between 4000-5000 RPM. Does anyone due this step?

I really am curious what caused that level of corrosion and I would like to prevent having to replace another exhaust manifold.

 

[FSH 210 Sport]

I recently had to replace the exhaust manifold on one of my engines due to a water outlet nipple being completely corroded and falling off. I do use it in saltwater, but I am the original owner of the boat and flushed the exhaust after every outing. I am beginning to wonder if my flushing procedure is incorrect or something else I am missing.

My flushing procedure seems similar to most on here: connect hose, start engine, turn on water, turn off water, turn off engine. I typically flush for no more than 2 minutes (1 min with freshwater, 1 min with saltaway) with the engine at idle. After the water is off, I will finish up by giving the engine a couple quick revs to get out any last water.

Looking in the Rotax operators and service manuals, they both mention running the engine about 20 seconds at a fast idle between 4000-5000 RPM. Does anyone due this step?

I really am curious what caused that level of corrosion and I would like to prevent having to replace another exhaust manifold.

What condition are the anodes in?

Perhaps your flush time needs to be increased and perhaps a more thorough salt away treatment?

 

[Dean P]

I recently had to replace the exhaust manifold on one of my engines due to a water outlet nipple being completely corroded and falling off. I do use it in saltwater, but I am the original owner of the boat and flushed the exhaust after every outing. I am beginning to wonder if my flushing procedure is incorrect or something else I am missing.

My flushing procedure seems similar to most on here: connect hose, start engine, turn on water, turn off water, turn off engine. I typically flush for no more than 2 minutes (1 min with freshwater, 1 min with saltaway) with the engine at idle. After the water is off, I will finish up by giving the engine a couple quick revs to get out any last water.

Looking in the Rotax operators and service manuals, they both mention running the engine about 20 seconds at a fast idle between 4000-5000 RPM. Does anyone due this step?

I really am curious what caused that level of corrosion and I would like to prevent having to replace another exhaust manifold.

I flush mine basically the same for 2 minutes max but do not rev the engines to 4500. I thinks that's crazy (and loud). But, what I always do, is to start them up again for 5 seconds after 5 minutes or so. This sudden rush of air help to flush out whatever water remains. I think this should be in the owner's manual instead of high RPMs (much easier on components).

 

[Dixemon]

I'm not familiar with the chaparral motors. What does the cooling hose go to? can you pull it off while you are flushing and see if anything is coming out of it? Most of these things corrode around the exterior of the nipple to hose mating surface. Can you provide a picture of the corrosion?
I have also heard of several members on this forum that like to run the motor after flushing with "No" water for around 30 seconds. I assume the theory is to allow the motor to get slightly warm, not overheat, to encourage the moisture left in the passageways to evaporate. That may be in theory what the rotax manual is trying to have you accomplish.

 

[Dean P]

I'm not familiar with the chaparral motors. What does the cooling hose go to? can you pull it off while you are flushing and see if anything is coming out of it? Most of these things corrode around the exterior of the nipple to hose mating surface. Can you provide a picture of the corrosion?
I have also heard of several members on this forum that like to run the motor after flushing with "No" water for around 30 seconds. I assume the theory is to allow the motor to get slightly warm, not overheat, to encourage the moisture left in the passageways to evaporate. That may be in theory what the rotax manual is trying to have you accomplish.

Our boats have a closed-loop system similar to you car/truck. The flushing is mainly to flush the exhaust. Running these boats out of the water is a bad idea (for extended periods of time) due to no water lubricating/cooling the impella bearings. Yamis are the opposite where the water does run over the bearing. Those can run forever or till you run out of gas.

 

[waternutt]

I flush mine basically the same for 2 minutes max but do not rev the engines to 4500. I thinks that's crazy (and loud). But, what I always do, is to start them up again for 5 seconds after 5 minutes or so. This sudden rush of air help to flush out whatever water remains. I think this should be in the owner's manual instead of high RPMs (much easier on components).

I agree. I tried running it up one time, but it sounded bad and I was not comfortable with it. I will maybe give the second quick startup a try to see if I get anymore water out.

I'm not familiar with the chaparral motors. What does the cooling hose go to? can you pull it off while you are flushing and see if anything is coming out of it? Most of these things corrode around the exterior of the nipple to hose mating surface. Can you provide a picture of the corrosion?
I have also heard of several members on this forum that like to run the motor after flushing with "No" water for around 30 seconds. I assume the theory is to allow the motor to get slightly warm, not overheat, to encourage the moisture left in the passageways to evaporate. That may be in theory what the rotax manual is trying to have you accomplish.

I don't have pictures, but the tech that did the repairs thinks it may have started between the hose and exterior of the nipple as you said. He showed me the part and it made sense to me. Just trying to figure how to flush/prevent it in the future. Of course, the manifold is a cast part so no replacing just a threaded nipple. Have to replace the entire manifold $$$.

 

[Dixemon]

short of rinsing the exterior of your motor with something like salt away. Then applying a corrosion inhibitor (ie. CRC-656, Boeshield t6, White lithium grease, ect..) you can always pull the hose off the fitting and apply something like LPS3, or a grease then reinstall. Maybe do it every year. That would be my suggestion.

 

[MD23679]

I flush mine basically the same for 2 minutes max but do not rev the engines to 4500. I thinks that's crazy (and loud). But, what I always do, is to start them up again for 5 seconds after 5 minutes or so. This sudden rush of air help to flush out whatever water remains. I think this should be in the owner's manual instead of high RPMs (much easier on components).

Thank you Dean P !!! This is exactly what I do with my boat and never had issues.