How to Freshwater Flush an Alpha One While In the Water (No Muffs)

I have been searching this forum and other internet sites and I can't find a definitive answer on how to flush the elbows (aka-risers) and manifolds on my 2005 Sea Ray 185 Sport (4.3l Alpha 1) while in the water and NOT using muffs. Biggest issue I believe is the Alpha 1 has the impeller in the outdrive.

I'm new to boating and want to start next year flushing after every trip. My boat has a hose fitting on the swim deck that I tried to trace yesterday but being it's behind the motor I couldn't verify the exact routing. I could barely see that it leads into an off-white plastic housing and then splits to two hoses. One hose I could tell leads to the T-Stat housing and the other I'm assuming goes to the PS Cooler and then down to the Outdrive impeller, which would be the raw water supply during normal operation. The sketch I attached is what I believe to be the coolant flow on my Mercruiser 4.3l.

Option A
My thought is that if I use the hose fitting for freshwater and don't run the engine then I would only be flushing the elbow and nothing else. Yellow path in the sketch. Depending on the water flow I risk having water flow into the exhaust and in to the cylinders. If I keep the water flow to a trickle I should be good, correct?

Is it true that the elbows corrode at a faster rate than the Manifolds? Maybe because they aren't flooded with water when not running and air enables more corrosion to occur? Not sure, but I read somewhere that elbows fail quicker/more often.

Option B
If I run the engine with the Freshwater supply connected, and the T-Stat is open, I would be flushing with a mixture of saltwater from the outdrive impeller and the Freshwater from the Flush fitting. Let me know if that sounds correct. If you look at the sketch then I would be able to have flow on the Yellow, Green and Orange path. The issue is that the impeller and Freshwater would be mixing at that plastic "T" that I spoke about and then a slightly less salty solution will be left in the engine. Seems better but not the best flush.

Option C
I read a few boat owners had installed a barbed fitting in to the drain plugs on the manifolds, then ran a hose from both of them to a "T" and then to a freshwater hose connection quick connect or capped hose fitting. They would shut the engine off, Hook up the hose and slowly feed freshwater into the system which would mix and flush the manifold and elbows. I'm really only concerned about those two parts as they are the two that need regular replacement due to corrosion. With this setup I would need to be careful of the water flow so I don't fill up any cylinders. I've never seen the inside of the riser to know how much flow it would take to do that. Maybe when I replace the manifolds this spring it will make more sense to me when I see the inner cavities of the elbows (risers).

Let me know your thoughts and what you feel is the best way to extend the life of the elbows and manifolds. Sorry but I couldn't figure out how to insert an image. I would choose the Jpg and then it would never show in the post so i had to make a PDF attachment.

raise drive, install muffs, lower drive, turn on water, run engine
option 2 is using three ball valves and two T`s
at water inlet cut hose ,install T, install shutoff going to a thru hull above the water line , T on other end gets a shutoff, that goes into the 2nd T, ,a shutoff then a water hose inlet fitting

from outdrive
I
I----S1----- to overboard discharge
S2
I
I ----S3--- to garden hose

To flush S1 open, S2 closed, S3 open

Too much thought is put into flushing engines....

I have a customer who had me install Quick silver flush kits on his 2016 SeaRay SLX W/Mercruiser 350 Mag MPI/EC engines when the boat was brand new.... He flushes the engines religiously with Salt-away.... Still had to replace his exhaust this past summer...

A salt water cooled engine block has a life span of about 22 years or so.... Your exhaust flushed regular or not will last 5-6 years.

Flowing seawater has a high corrosion rate.... Most exhaust corrosion happens when the boat is underway, not sitting.

Think of it this way. Your time costs money. Maintenance is about $100 an hour plus parts whether it's your time or someone else's. Now think about exactly how much time you put in to "flushing" over the course of the 5 years you will get out of a set of risers and elbows. I think you'll find it doesn't add up to any savings at all.

Bt Doctur said:

raise drive, install muffs, lower drive, turn on water, run engine
option 2 is using three ball valves and two T`s
at water inlet cut hose ,install T, install shutoff going to a thru hull above the water line , T on other end gets a shutoff, that goes into the 2nd T, ,a shutoff then a water hose inlet fitting

from outdrive
I
I----S1----- to overboard discharge
S2
I
I ----S3--- to garden hose

To flush S1 open, S2 closed, S3 open

Click to expand...

Doc!
Thank you - I forgot to put that one in as option #4. As I was dozing off in to a slumber my eyes opened up and I thought...Damn! I forgot to include option 4!. ha ha ha. I did read that one on this forum and your description and schematic clarifies how to do it. Thanks again for the reminder and suggestion. That option allows the engine to be running, impeller to be spinning freely without fear of back pressure or saltwater mixing with fresh, and to fully flush the entire engine with freshwater. I wish putting on muffs was less of a PITA for my boat or I'd use that method.

o2batsea said:

Think of it this way. Your time costs money. Maintenance is about $100 an hour plus parts whether it's your time or someone else's. Now think about exactly how much time you put in to "flushing" over the course of the 5 years you will get out of a set of risers and elbows. I think you'll find it doesn't add up to any savings at all.

Click to expand...

That is a good way to think about and after I try to do it a few times I'll probably justify not doing it using that logic. Until then, I think I'll add that system that Doc mentioned above and crack a beer and watch the flushing process...one beer should be the right amount of time to let the freshwater flush out the salt. Thanks for the reply!

Docksidemarineservices said:

Too much thought is put into flushing engines....

I have a customer who had me install Quick silver flush kits on his 2016 SeaRay SLX W/Mercruiser 350 Mag MPI/EC engines when the boat was brand new.... He flushes the engines religiously with Salt-away.... Still had to replace his exhaust this past summer...

A salt water cooled engine block has a life span of about 22 years or so.... Your exhaust flushed regular or not will last 5-6 years.

Flowing seawater has a high corrosion rate.... Most exhaust corrosion happens when the boat is underway, not sitting.

Click to expand...

You are probably right and your opinion is much more valuable than mine, which only has a few months of boating experience. Just like my reply to O2, I'll feel better flushing and trying to extend the life of those components. I'll be replacing my manifolds so I'll be familiar with the routine (OEM MerCruiser Dry Joint at $400 a pop - no aftermarket since these originals lasted 16 years somehow!!!).

Then I plan on removing, cleaning and inspecting the elbows and manifolds every couple of years before the spring launch at the cost of gaskets and my time. All the reading/research and discussion with mechanics I've been doing says the cleaning/inspection is time well spent. And many (probably 100%) of those people I spoke to said I won't have this boat more than 3 years before upgrading anyway....I think they are correct as well. Pretty sure the next boat will have an Outboard!

Thanks for the reply

Boating is not a cheap hobby. Count on 500 dollars for every meter of length per year, minimum.
Those 1 inch stainless ball valves are $250 each. So spending nearly a thousand dollars (including stainless nipples and clamps) seems sorta ridiculous.
You could save by using the Groco marine bronze, at roughly $80 each, but they will turn green and nasty in a year or so.

o2batsea said:

Boating is not a cheap hobby. Count on 500 dollars for every meter of length per year, minimum.
Those 1 inch stainless ball valves are $250 each. So spending nearly a thousand dollars (including stainless nipples and clamps) seems sorta ridiculous.
You could save by using the Groco marine bronze, at roughly $80 each, but they will turn green and nasty in a year or so.

Click to expand...

Yikes for SS $$$!!! Completely agree with you on that one.

How about Schedule 40 PVC? It can certainly handle the pressure and it's impervious to damn near anything. I'd be hiding the valves anyway so it doesn't need to look all pretty with shiny SS. That weird connection that I described in my original post, where the fresh water hose joined the line from the raw water hose, is plastic so it's held up for 16 years. Any reason not to use PVC?

BHW-Mike said:

Yikes for SS $$$!!! Completely agree with you on that one.

How about Schedule 40 PVC? It can certainly handle the pressure and it's impervious to damn near anything. I'd be hiding the valves anyway so it doesn't need to look all pretty with shiny SS. That weird connection that I described in my original post, where the fresh water hose joined the line from the raw water hose, is plastic so it's held up for 16 years. Any reason not to use PVC?

Click to expand...

Eventually the PVC will crack and break. My friend had a plastic engine flusher on his crack while underway. Noticed overheat starting opened hatch to find he was sinking due to water coming in broken fitting. No place for plastic

No plastic!!!

So no PVC. Got it. I'm not sure where I would be adding this due to the size of it, but does anyone know the size of the hose going to the PS cooler? Is that a 1" ID? If it is I found 1" SS 3-way valves for $50 and 1" hose barbs for $12. Using those it would be about $150 total. Only two valves to turn to divert or flow straight through. A bit cleaner and less components/connections.

Look I don't want to be a wet blanket to your notion, but this is a somewhat dangerous idea as far as being certain of your cooling water flow. As much as you'd like to maintain your engine (and I don't want to discourage you there) this configuration can too easily lead to a situation where you think it's OK when it isn't. It would be a real shame to have your engine overheat and strand you out in open water, not to mention life-threatening. If this was a thing, believe me, every manufacturer would be installing these diverter valves on their engines. They don't for the very reason I mention.
If you are that worried about having to spend a few hundred every now and then, look for the stainless elbows that fit your engine and install those. That'll be one and done and you can move on to worrying about other points of failure ha ha.
I also hope that you will stop being so concerned about the cost factor of using your boat. These boat parts are expensive for the same reason airplane parts are expensive...they must withstand the rigors of a harsh environment and still reliably get you home. It isn't like a car that you can just walk if it breaks down.
This is a health and safety item. Spend what it costs and look at it for what it is: the price of enjoying the water. If it's too much, then get out while you can and just rent when you get the urge.
PS wear your PFD! We just lost a waterman on the weekend who was tonging oysters from his 18 foot Carolina Skiff in Slaughter Creek. If he had his Mustang on, he'd be alive today. I guess he felt confident he'd never fall in.

PPS I wouldn't have those cheapo valves on any boat of mine. You get what you pay for and those are probably not marine-grade stainless. They will rust without a doubt. Or crack, or fail in some other way.

Read post #3 again.