Flush Time

Pcola200

New Member
May 17, 2008
38
Pensacola, FL
Boat Info
1993, Model 200 bowrider
Engines
4.3 LX Mercruiser w/Alpha One drive
How long should it take to adequately flush my 4.3 LX Mercruiser and Alpha One outdrive? I run in salt water and flush with muffs first thing when I am back home. The manual tells me to apply a steady but not full flow from the garden hose and wait until the exhausted water runs clear. I cannot tell when it is clear. It takes 4 or5 minutes before water even starts coming out of the exhaust ports and then about 1 minute after that my alarm starts going off because my temp gauge is pegged. It doesn't seem to me that the system is getting flushed completely. Maybe I need a better set of muffs, mine is a universal style with the hose only connected to one side. Maybe I am not getting a large enough volume of water???:huh:
 
15 minutes is what I do. We have clear water here, so 15 minutes seems suffice
 
Water should be turned up more I think. Whens the last time checked/changed your impeller? Have you ever run the engine without the hose on or not in the water, even for a second? I would also check your thermostat, it should not be setting off alarms. make sure your foot is all the way down also when running the engine ever... Good luck!
 
Pcola,

You should see water flowing out the exhaust ports within about 15 seconds or so. Typically you don't want to use full flow from the garden hose. However, you do want to see a good solid stream of water. Also water psi varies from city to city, neighborhood to neighborhood and etc. I use a set of Quicksilver muffs. They have a pin that inserts through the outdrive intake. So, the muffs won't slip off. Once the engine reaches its operating temp, I continue the flushing process for another 5 minutes and then shut her down. This way, you know the thermostat has opened and the block has been flushed as well.

Also, make sure you turn the water on before starting the engine. Afterwards, shut down the engine and then turn off the water.

As a minimum, I would suggest having the impeller replaced by a qualified tech before your next run. How have you flushed the engine in the past? Has this ever been a problem before?
 
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Engine should not overheat or even exceed normal operating temperature when flushing. I run in salt water all the time and flush regularly. You need enough water pressure to see water coming out the exhaust within seconds! not minutes! I flush for about 10-15 minutes to make sure the thermostat opened and normal operating temp is reached. Can't stress enough if you overheating while flushing you are doing something wrong.
 
Something isn't right..............You need to be sure you are using the correct muffs for an Alpha drive. Muffs that don't fit allow the pump to suck air, not water, and if there are cooling water intake holes that are not covered, you can lose waterbefore it even gets to the engine.

How long? Until the engine reaches normal operating temperature and your thermostat opens. Only then are you flushing your engine. Up to that point and the cooling system by-passes all the cooling ater and no fresh water enters the engine. Back when I was doing outdrive boats, I used flush for about 15 minutes after the engine got to temp.
 
Make sure that you still have excess water spilling from the muffs AFTER the engine is running. If not you need more water flow.
 
Something isn't right..............You need to be sure you are using the correct muffs for an Alpha drive. Muffs that don't fit allow the pump to suck air, not water, and if there are cooling water intake holes that are not covered, you can lose waterbefore it even gets to the engine.

How long? Until the engine reaches normal operating temperature and your thermostat opens. Only then are you flushing your engine. Up to that point and the cooling system by-passes all the cooling ater and no fresh water enters the engine. Back when I was doing outdrive boats, I used flush for about 15 minutes after the engine got to temp.

Here's the one I use and it works great.
QuickSilver Mercury / Mercruiser Part: 44357Q 2
44357Q2.JPG


It has a pin the goes through the intake holes where you put the muffs and holds it secure.
As stated before you should have water kicking out really quick.(somehow I read right over that before)
 
I also used the one with the pin. I always taste the water to determine when it's clear. 10 - 15 minutes is about right. If you have a lot of systems that run off hot water from the engine (hot water heater, cockpit heater), I found that bumping the throttle up off of idle a little (I used 1000RPM) did not collapse the hose and provided thorough rinsing for the accessories as well as the engine.

It really sounds like your ear muffs don't fit well enough. You are probably running your engine dry. The impeller is likely toast. You may be causing damage. Change what you are doing before something expensive happens. Good luck.
 
Thanks for all the replies. This is my first boat and I am not sure of all the past history in regards to repairs and maintenance and I am learning how to do things as I go. I have had her out a half dozen times for approx 12 hours of actual run time. Idles good, accelerates nice and smooth and has never overheated while in the water. I have been using the muffs that came with the boat and assume the previous owner used them also. They are a rectangular design with water inlet on one side only. They don't fit perfect, so I usually squeeze them a little bit with one hand while I regulate the flow with the other hand trying to find the best combination to get water out of the exhaust asap. Like I said before, the temp goes up and the alarm goes off before I can let it run for enough time. I only idle the engine while trying to flush. If it had a bad thermostat it would overheat in the water, which it doesn't. Maybe The muffs are my problem, I will get the correct one at West Marine. What about the impeller that has been mentioned, how do I check to see if it is functioning correctly and is it a DIY item to R&R???
 
The impeller is a do-it-yourself item, if you would put a new starter on a car. If not, it's about $250 at a service center. It's a rubber, star-shaped device that is engine driven and rotates inside a housing to draw water up out of the lake to the engine for cooling. Most people replace them annually anyway.
 
Pcola,

I have the same flush kit as Nehalennia. Works great and its essentially idiot proof. The ones that simply slide on can fall off. Happened to me years ago.

As others have stated, yes you can change the impeller provided that you are mechanically inclined. It also helps to have someone who has done it before to help. I would suggest getting the Merc. manual for your engine/drive model. You will find that the impeller is contained within the lower unit of the drive. If you are going to do this you should replace the impeller rather than just "check it."
 
Also, by the time I start the engine, and stick my head over the swim platform the engine is or has just started flowing water.
 
........ Maybe The muffs are my problem, I will get the correct one at West Marine. What about the impeller that has been mentioned, how do I check to see if it is functioning correctly and is it a DIY item to R&R???

Well if your temp is good on the lake, then you may be OK and your muff simply aren't supplying enough to cool properly.
Doing this may burn your impelller up, so get the proper muffs I mentioned ASAP.

Keep an eye on your temp and make sure it stays consistent.
 
I'm not sure how accurate the temp gauge is, but it runs right around 170 at cruising speed and a little warmer when idling, but still way under the 190 degree mark, is that normal? If so, then maybe the impeller is OK and it is just a poor quality muff that I was using. I did some reading on past threads discussing the impeller and looked at some links that were posted for the mercstuff and sterndrives websites. The whole procedure looks fairly strait forward and providing that you have all the replacement pieces on hand, the job should be able to be completed in a day. I'll try a new muff first though, no sense tearing something apart if it doesn't need to be.
 
Your temps sound very normal to me. Def'ly try the muffs. Hopefully, all is well.
 
It was definitely the low quality muffs I was using that was the problem, so in the trash they went. I picked up the same model that Nehalennia suggested and they work great. Fired her up today and the temp stayed at 150-155 while I flushed the system for 10 minutes. So I assume that the impeller is fine. Is there any solution that I should run through the system when flushing to try and counteract any salt water that was left in the system from my previous flush attempts?
 
I am still waiting on someone to post a video on our CSR youtube site on how to properly flush the engine of an I/O. :huh:
 
Salt-Away is a product of which I've heard. It's not cheap, but it neutralizes salt and helps rinse the motor clean. From my 10 years experience with flushing my SR 250DA, you don't need it. If you feel you're behind the power curve, you may want to use it once or twice to clean things out real well, then just stay on top of it with fresh water after that.
 

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