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Recently purchased a new to me Pro Line 24 Supersport with a 2006 225 Optimax. I'm getting conflicting info on the proper way to flush out the engine. Some say to attach the the hose to the adapter that screws into the back of the motor and others say to use the ears on the lower unit. Does it really matter or is one way better than the other?
__________________ 2006 Proline 24 SS w/225 merc optimax
"Never take life seriously, nobody gets out alive anyways."
I just have a little 90hp merc...I hook it up to the fitting on the motor and rarely use muffs. You will continue to get mixed feelings about this topic.
according to the manual the rear flush attachment is NOT to be used with the motor running. I would flush mine with the attachment while in the water. I kept it in a slip and used the ears when i had it on the trailer,
__________________ RETIRED Fire Officer
Swansboro, NC
Key West 2300
F250
Part of the reason you’re getting conflicting information is that Mercury used to say that it was OK to run an OptiMax while using the flush port. From the manual for my ’98 Opti: “Note: Engine can be stopped or running at idle speed when flushing the cooling system. Do not flush engine using a water system that exceeds 45 psi.”
Perhaps things have changed on the newer models.
__________________
'99 Boston Whaler 18 Ventura
135 OptiMax
I called the Merc factory and asked them. They said they would run it on the muffs. If you use the port, you are not flushing the water pump impeller or the passageways up to the powerhead.
__________________ "Lickety Split" 31 Fountain with 250 efi's
Part of the reason you’re getting conflicting information is that Mercury used to say that it was OK to run an OptiMax while using the flush port. From the manual for my ’98 Opti: “Note: Engine can be stopped or running at idle speed when flushing the cooling system. Do not flush engine using a water system that exceeds 45 psi.”
Perhaps things have changed on the newer models.
Nope, that's exactly what is says on page 57 of my manual. Manual is dated 2005 and refers to 200/225 Optimax. Looks like I'll be using the muffs, thanks for taking the time to help me. Kinda new to these larger motors, currently running a 60 hp E-tec on a flats skiff so this is a big step up for me. I'm sure I'll have many more questions.
__________________ 2006 Proline 24 SS w/225 merc optimax
"Never take life seriously, nobody gets out alive anyways."
I prefer muffs. Reasoning is since I am running saltwater with it circulating hot through the motor running warm/hot freshwater would be the best way to remove salt deposits in the block.
__________________ Babesaurus Talon F20/300xs Dolphin Skiff/175 Merc
I believe that you obtain a more effective flushing with the muffs and the engine running at idle speed. It is easier though to just attach the hose to the back port and flush without running. The reason the manufacturer suggests doing it that way is because it is easier and more convenient, not because it is better for the motor.
I am the original owner of a 2000 200XL Saltwater Optimax and have used muffs on this trouble free engine for 9 years now....have never used the hose hook up feature.
I called the Merc factory and asked them. They said they would run it on the muffs. If you use the port, you are not flushing the water pump impeller or the passageways up to the powerhead.
Don't know who you talked to but this is simply not true. In fact the first place the water goes is up through the powerhead. Fuel rail, compressor, etc. Everything gets flushed. Water flows quite freely out of every exit/entry point including the water impeller housing and low water pick up when hooked up to the adapter. The engine must be in a vertical position however.
This holds true for the Opti's. Not sure about the EFI's or Verados so I won't include them in my discussion.
If you read your coolent flow chart in the merc manual you will see every thing gets flushed with the adaptor .
I use the plug on the back with the merc restrictor , and flush it with salt away every time ,
When you run on the muffs its a good idea and recomend buy merc to use the rubber nose cover that straps on the low water pick up . to prevent it from over heating
700 hours on my 250 pro xs and not a spec of salt or corrsion in waterpump or ect.,, When pulled to grease shaft and replace water pump as a over due maitance project .
I only use muffs if i need to have engine running for some reason , never for flushing , and my boat is salt water off shore only
I made a adaptor so the restrictor is not right at moter as it can be a little tight to get back out of the engine and salt away goes on easy also
( plastic ends on a short peice of garden hose that plugs into moter and ) I would not recomend running engine on th adaptor , only muffs
The tatle tale strem on these moters is the only cooling source for the compressor . so i only run on muffs if i have to ,
__________________ If its on the back it better be mecury black because the race never ends .
2 stroke because 4 strokes are 2 to many and 1 is not enough
yes your suzuki has tons of toqure because its geared high enough to make a weed eater pull a house .!!!! Did you change your oil yet boy ???
I flush from the back of the motor, 2001 Opti, with hose on water comes out of all the orifices. never had any problems with water pumps or overheating (probably just did myself)
Running the engine on the flush port is not a good idea. That impeller is pushing water up the water tube as the water is trying to come down the same tube. Any water that enters the pump housing is being pushed back against what the pump is pushing. The only other intake for the water is the water inlets on the gearcase which are introducing air.
I am aware of what the factory says but I just dont think its the best idea. Water pumps are very durable and they will last while doing this but flushing them with muffs/in a bucket is better then the flushing port.
I dont belief that you can successfully argue that the flush port is better then the muffs or submerging the lower unit in a barrel.
Best way to flush a Merc Optimax 
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