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Rear threaded fitting on my Bigfoot
randolphp	#1  Posted on 07/24/16 - 10:51 AM
Member Posts: 74 Comments: 0 Joined: 10/31/14	2007 Sport 150 and 2007 60 hp Mercury Bigfoot I connected a hose to the rear threaded fitting and started my Bigfoot but no water came out of the water pump indicator hole so I quickly turned off the engine and reverted to the earmuff method of flushing my engine. I want to use the threaded fitting instead of the earmuffs. I need to know why no water came out of the indicator hole. What can I do or what am I doing wrong?
fitz73222	#2  Posted on 07/24/16 - 4:48 PM
Member Posts: 67 Comments: 0 Joined: 02/23/16	Most flush ports that are used are meant to back flush and do not run the engine. You can fry the water pump, I don't use them because it will not flush out the thermostat since it is closed when engine is not running. Flushing with muffs and the engine running is the best way to flush the engine for about 10-15 minutes. Flush ports are great for when the boat is moored in saltwater., something is better than nothing.
randolphp	#3  Posted on 07/25/16 - 3:27 AM
Member Posts: 74 Comments: 0 Joined: 10/31/14	I believe you are right but pgs. 70-71 of my owner's manual show a hose connected to the fitting and the text suggests that the motor must be running at idle in order for the engine to flush properly. Because of what I read in the manual, I'm led to think that the fitting serves the same function as the earmuffs but no water flows out of the indicator hole when I use the fitting and I don't think that's safe - I think that means that the pump is not being cooled by flowing fresh water. The text suggests that it's OK to run the engine when a hose is connected to the fitting. I believe , however, that you are right but I'm still a little confused by the conflict between your explanation and what is written in the manual, which I presume was written by Mercury engineers.
EJO	#4  Posted on 07/25/16 - 4:19 AM
Member Personal Page Posts: 669 Comments: 6 Joined: 11/25/12	I believe because you hose connection covers up the tell tale stream the only way you know water is going through the engine is the water coming from the exhaust(center of propeller) Therefor if 'flushing' while in the water you can tilt your engine out of/above the water as the water hose is supplying the cooling water. Skipper E-J m/v "Clumsy Cleat" a 2008 Montauk 150
randolphp	#5  Posted on 07/25/16 - 10:22 AM
Member Posts: 74 Comments: 0 Joined: 10/31/14	The boat is out of the water now and I was flushing the engine (in a vertical position)in preparation for storage in late August. The fitting and the indicator are two different apertures so the hose was not covering or obscuring the stream that comes out of the indicator hole. The fitting is above the indicator hole, as in the illustration on page 71 of the owner's manual. Are the muffs and the fitting used for two separate functions? Which is more reliable: fitting or muffs? So far, I think the muffs are more reliable. Depending on the fitting for flushing during maintenance seems pretty risky.
Phil T	#6  Posted on 07/25/16 - 12:48 PM
Administrator Personal Page Personal Album Project Albums Posts: 7043 Comments: 6 Joined: 03/26/05	DO NOT RUN THE MOTOR when using the flushing port. Only when using the muffs over the water intakes on the lower unit.
randolphp	#7  Posted on 07/25/16 - 4:09 PM
Member Posts: 74 Comments: 0 Joined: 10/31/14	I promise!
fitz73222	#8  Posted on 07/26/16 - 2:08 AM
Member Posts: 67 Comments: 0 Joined: 02/23/16	I just want to put some logic behind this discussion that makes sense for everyone who contemplates the flush port issue. The rubber impeller down in the gearcase is designed to draw cooling water through the intake grills on the sides of the gearcase, compress the water and push it up the water tube into the powerhead to cool the engine. When using muffs there is not enough water pressure to get the water to the powerhead without running the engine and pumping water up. Using the flush port from above is designed to flush out the powerhead and reverse flow water through the block, down the wet side of the exhaust and down the water tube into the pump and back out the intake grills. The problem with running the engine with flush port is that the water is coming to the rubber impeller from the opposite direction. So you are trying to force water back into the pump and the pump by design is trying to push water up creating a water starvation issue, some water is making it to the top of the pump but where the impeller rides on the wear plate beneath is starving for water since nothing is coming in from the intake grills. So over time from the rubber getting hot from lack of water lubrication the rubber will start to transfer to the stainless wear plate and start to disintegrate the pump and increase the gap between the wear plate and impeller and start to loose its ability to seal and draw water resulting in water pressure loss at high speed. Now as I mentioned, the fundamental issue with flush ports is that since the engine is not running and at operating temperature, the thermostat remains closed so the flush port water hits a dead end and cannot circulate as designed, this is why the engine overheats when running with a stuck thermostat because the cooling water flow is interrupted and can't transfer block heat to the water circulation. The flush port is a great idea if the boat is moored in salt water or you have noise restrictions in a residential neighborhood. One thing to mention about flush muffs is don't ever leave them alone when flushing the engine because they can walk off the intake grills and starve the pump for water and fry it. In other words, stay with boat when it's running, I like to empty the gear out in preparation for wash down and keep an occasional eye on the tell tail (pisser) as I get the gear out. It takes me about 15 minutes to get the boat empty so when the gear is out, the engine is flushed and I shut it down. Hope this helps...
randolphp	#9  Posted on 07/26/16 - 5:55 AM
Member Posts: 74 Comments: 0 Joined: 10/31/14	I understand: The fitting has value for a certain purpose and the muffs have value for another purpose. Out of the water and for maintenance the muffs should be used. There really is no reason to use the flush fitting when the boat is on land. I do not have the opportunity to flush my engine after each use at a dock so I will probably never use the flush fitting.