Flushing Sea Ray 250 Sundancer in salt water... How To, and is it necessary?

Hi all,

I have a 1998 SeaRay Sundancer 250 w/a 2006-ish (maybe 2005-2007) mercruiser MPI 5.0L and a Bravo 3. I keep it in a saltwater marina.

My boat has a little flush port on the rear of the transom. I can hook up a hose, and this port ties right into my cooling system. Just a few questions:

1) Is this enough to flush the engine with fresh water? I have been hooking up a hose and turning the water on and running the engine for a few minutes, but in retrospect, I'm not sure if that's enough or if this is the proper way to flush my engine.

2) If I need to do more, is there a good kit that I can install? I've heard good things about the perko valve and also this quick flush valve (since it can also backflush the outdrive, if that matters): https://www.quickflushvalve.com/. Just not sure what's best. I would want to add that salt away feature eventually if I need to be flushing my engine a lot.

3) Do I even need to flush my engine if my boat is in a saltwater marina year round? I was reading through this thread and there seems to be a lot of agreement that for a boat that stays in the water, even saltwater, you don't need to flush it because the salt just stays in solution. I have no idea if that's true or not so I'm trying to recruit as many opinions as possible. Here's the thread (from ClubSeaRay): https://www.clubsearay.com/threads/in-water-engine-flush.5945/

4) I guess the last question is... that quickflushvalve just some brass fittings, or am I missing something? To me, it looks like I could just build this myself with brass fittings from Lowes. Has anyone just done this? Or is there something about it that I'm just too dumb or naive to see that makes it worth the $240+ that they charge for the valve?

Thanks!!

When you stop your engine most of the cooling water drains out, leaving air and salt water in the interior. It's much better corrosion-wise to run fresh water through your engine before shutdown. You may be able to just turn on the hose without running the engine to get the benefit. Not sure.

When you say stored in a marina, is it docked or in dry storage?
When you shut the engine off actually the engine stays full of water and so do the exhaust manifolds, some drains out of the exhaust elbows though, that's why they rust the worst, because they are now exposed to air with salt residue.
Any flushing you can do will help. Where I keep my boat I can't really flush it (salt water mooring) so I just flush it at the end of the season, and fill it with the best AF I can find for winter storage. And with all that, it's lasted a LONG time. But that's a 5-6 month season not 12 months. That long for a sterndrive in the salt, I'd have to pull it at least 2x a year to clean the growth off the outdrive and clean out the water intakes, at least, most likely touch up the antifouling because the paints for aluminum don't last that long.
Ultimately a closed cooled engine is the way to go but that's only practical if you're starting with a new or reman engine with no flaking rust inside.

I ran a superflush system on my last searay. it was the SF-400 https://www.superflushsystems.com/

simply hook up a garden hose, turn it on, and you can flush while in the water.

The other system I have used is the Neutra-Salt system developed for volvo pentas. it injects a salt-neutralizing solution that chemically neutralizes salt in the water jacket.


I highly recommend flushing at a minimum. however to answer your question:

searay250 said:

Hi all,

a Bravo 3.

Has anyone just done this? Or is there something about it that I'm just too dumb or naive to see that makes it worth the $240+ that they charge for the valve?

Thanks!!

Click to expand...

a 1-1/4" Tee fitting AFTER your raw water pump (before the thermostat housing) with a ball-valve and an RV water connection and you can build a flusher for about $30

Horigan said:

When you stop your engine most of the cooling water drains out, leaving air and salt water in the interior. It's much better corrosion-wise to run fresh water through your engine before shutdown. You may be able to just turn on the hose without running the engine to get the benefit. Not sure.

Click to expand...

Interesting. Yeah this makes sense, although to @Lou C's point, is this mostly for dry docked boats? I wonder if boats that stay in water just keep their water for the most part.

Lou C said:

When you say stored in a marina, is it docked or in dry storage?

Click to expand...

Ah sorry, yeah it's docked. I guess that was confusing phrasing. It's docked in saltwater.

But good to know that flushing after every trip isn't strictly necessary for a boat docked in salt, thanks! I'll probably try to do it regularly just in case but glad to know if I forget it's not like I'll need a new engine or anything haha.

Scott Danforth said:

The other system I have used is the Neutra-Salt system developed for volvo pentas. it injects a salt-neutralizing solution that chemically neutralizes salt in the water jacket.

a 1-1/4" Tee fitting AFTER your raw water pump (before the thermostat housing) with a ball-valve and an RV water connection and you can build a flusher for about $30

Click to expand...

Thanks! I'll plan on the neutrasalt system as well. I guess I'll just add a tee fitting and make my own valve system.... appreciate the tips. By "RV water connection," do you mean just like a garden hose hookup?


Thank you, all!

Scott Danforth said:

a 1-1/4" Tee fitting AFTER your raw water pump (before the thermostat housing) with a ball-valve and an RV water connection and you can build a flusher for about $30

Click to expand...

So... it turns out I have questions about this. Maybe they're dumb ones!

One, it sounds like you're suggesting putting it "after" my pump... I have a bravo 3, so my impeller is on my engine. Do you mean putting it between my impeller and my thermostat? Is that right?

Two, what happens if my flusher ties in before the impeller? Currently, I just have a passive flush port that goes to a T fitting with no valves or anything, and it's before my impeller. Is this a problem? Can a garden hose move my impeller? I assume not.

Three, and I should have thought about this, but... if I put this flusher before my thermostat, wouldn't the thermostat need to open in order to flush the whole engine? I guess that means I need to actually run the engine, right? Or am I missing something here?

Four, what material is recommended for a fitting? My instinct is to use something like 316 stainless or bronze or something, but that's way more than $30. Bass is cheaper but could corrode, I think? PVC might work and could be around $30 but things will get bad if it melts. This will have salt water passing through every minute the boat is on, so I'm just not sure what the right material is for something like this.

Thanks!

If you have the flusher before the pump, you need to have the motor running to be able to flush it

That means your garden hose MUST supply a lot more water than the raw water pump is moving, and hoses on the dock simply do not have that flow or much pressure. You need to have about 10 GPM of hose flow available to put the flush tee before the raw water pump

So if you simply want to flush out the salt water while docked and the motor off. You plumb the flush port AFTER the raw water pump and before the thermostat housing. The exhaust will get fully flushed and the motor will be partially flushed (due to the bypass in the thermostat housing)

This is where kits like the Superflush products shine, they have 4 or more ports that go to various locations after the thermostat and flush the motor without it running

Then there is the neutral salt system. You inject chemicals BEFORE the raw water pump. Hold the button for 45 seconds as you are idling, then key off. The raw water pump moves the chemical thru the motor

Scott Danforth said:

If you have the flusher before the pump, you need to have the motor running to be able to flush it

That means your garden hose MUST supply a lot more water than the raw water pump is moving, and hoses on the dock simply do not have that flow or much pressure. You need to have about 10 GPM of hose flow available to put the flush tee before the raw water pump

Click to expand...

Thanks for the detailed reply! sorry for my ignorance, but I'm a little confused about something. This makes it sound like IF things are plumbed in prior to the impeller, a garden hose just won't cut it. But my understanding was that it's totally fine, and even a good way to flush, to hook up a garden hose via muffs to a running engine... which, at least when I do it, leaks a fair amount of water out so even less water is going to the pump... plus some pressure is lost in the muffs. How could it be the case that a garden hose that's tied directly in via a hose port, where 100% of the water is going to the pump with full garden hose pressure, isn't sufficient to run the engine? It seems like if muffs work, a direct tie in is even better.

The only reason I'm asking is because I would love to find a way to run the engine while I flush it, but all I have is a garden hose hookup so I want to make sure that's sufficient.

Thanks!

I wouldn't worry too much about the flushing, yes do it if you can, but honestly I have never seen any of the inboard boats moored where I am (there is a dock with a hose) get flushed. While I'm sure it helps, saltwater use with a cast iron block gives you at most, 20-25 years at least here with our level of salinity.
When I did a top engine overhaul some years back (past overheat damage, head gaskets finally started leaking) this engine was run in the salt (moored too) for about 17 years, and what I found was the block cooling passages were evenly coated in rust, not much flaking but the cyl heads seemed to have more corrosion around the cooling passages. At that point the machinist I took them too felt replacing them with a set of reman heads was the best plan so that's what I did, and I have heard of cyl heads rotting thru behind a valve seat and hydrolocking the engine. The other thing is the intake manifold, at the end of each season, I remove the 'stat housing and probe that water passage below the 'stat, if this rots thru, it will put water right into the motor oil via the cam valley.
Lastly you have to inspect that exhaust system and figure on replacement after 5-7 seasons, do not neglect this, leaking salt water into the cylinders will lock up an engine fast.
Best advice is to do an oil analysis at the end of each season when you change the oil, you will see if sodium is showing up in the motor oil, if so it's a sign that needs to be investigated. Could be head gaskets, could be intake, could be exhaust.

In fresh water wher I boat. Engine temperature above145 starts minerals sticking to hot parts. Do WOT for several minutes ? It is baked onto motor castings. Add in a lugging motor and load of people. Oh well.
Salt water I have no idea.

searay250 said:

How could it be the case that a garden hose that's tied directly in via a hose port, where 100% of the water is going to the pump with full garden hose pressure, isn't sufficient to run the engine?

Click to expand...

garden hose can not push much past the raw water pump unless the pump is turning. so unless you are running the engine, wont work

muffs only work when the engine is running, because without the engine running, the water pressure just sprays out past the muffs. if you try to push water past the raw water pump with a 70-110psi garden hose, then expect to push the seals out of the raw water pump

if you are running the engine, and the flushing hose can not keep up with teh demand of the motor, you are no longer displacing salt water and just watering it down, then at that point, dont even waste your time attempting to flush. use a system like the neutra-salt system

cyclops222 said:

In fresh water wher I boat. Engine temperature above145 starts minerals sticking to hot parts. Do WOT for several minutes ? It is baked onto motor castings. Add in a lugging motor and load of people. Oh well.
Salt water I have no idea.

Click to expand...

I have heard this for years. When I pulled my engine apart with 100% salt use guess what? Nothing besides rust! The salt is not the issue it’s calcium. Salt dissolves in water! And, as is common with OMCs & Volvos I ran a 160 stat all those years! I tried a 140 & did not like it; engine took forever to warm up & I had condensation in the exhaust system. So based on 20+ years in salt I’m saying while it can happen it has not happened to me!
The only time I ever had elevated temps was when I had marine growth in the water intakes common on
boats moored or docked in salt water. To combat that I removed the plastic screen OMC put in the water intakes and I can rod out the holes in the lower unit with a piece of coat hanger wire by hanging off the swim platform. Had to do the same thing for my brother last summer. His 2020 Merc 4.5 started running hot & went into protection mode. Then I taught him the coat hanger wire trick!

A important CHEMICAL NOTE !
Very polluted industrial waste water. Most major cities and industries can have UNEREAL toxic chemicals and minerals that do stick to really hot engine parts.

Lou C said:

Lastly you have to inspect that exhaust system and figure on replacement after 5-7 seasons, do not neglect this, leaking salt water into the cylinders will lock up an engine fast.
Best advice is to do an oil analysis at the end of each season when you change the oil, you will see if sodium is showing up in the motor oil, if so it's a sign that needs to be investigated. Could be head gaskets, could be intake, could be exhaust.

Click to expand...

Yep, this makes sense, thanks! Just one question. You mentioned a "sodium analysis" as the best advice. Does this mean that if I do a sodium analysis at the end of each season, assuming I use my boat mostly on the weekends so it's not like I'm flying through hundreds of hours a week as a commercial trawler or anything.... this should give me advanced notice of any issues with my head leaking, my intake, or, the one I'm most worried about, the exhaust?
I know that catastrophic failures happen, I understand that there are edge cases... I'm not going to come back and yell at you if my boat is the one in a million where something goes wrong! But *in general*, is a sodium analysis the "best practice" for knowing when my exhaust manifolds or whatever will need to be replaced? I was worried I was going to either have to be always taking them off and inspecting them or replacing them every few seasons just to be safe, but if there's some kind of test that will give me some advanced warning about when they'll need replacement, and I only have to do it once a season, that's kind of best case scenario for me

Scott Danforth said:

garden hose can not push much past the raw water pump unless the pump is turning. so unless you are running the engine, wont work

muffs only work when the engine is running, because without the engine running, the water pressure just sprays out past the muffs. if you try to push water past the raw water pump with a 70-110psi garden hose, then expect to push the seals out of the raw water pump

if you are running the engine, and the flushing hose can not keep up with teh demand of the motor, you are no longer displacing salt water and just watering it down, then at that point, dont even waste your time attempting to flush. use a system like the neutra-salt system

Click to expand...

Ahhhh okay, I see the miscommunication, thanks for clarifying. I should have been way, way more explicit about what I am currently thinking.

By now, I think I'm going to take... actually, looking back, *your* advice (thanks!!) and build my own tee valve and plumb it in. But, I am going to build it similar to the quick flush valve. So, this means it will have three modes:
1) The tee is there, but doing nothing, so the hose inlet is closed off. I would use this when running the boat normally, so salt water just runs through the tubes like normal.

2) I would build a valve so that the hose inlet can push water right out of the drive, so basically backflushing the drive. This would open the hose port but close off the line that goes to the water pump, and I would only use this passively (so... engine off). This is just to backflush the drive as much as possible with fresh water.

And then there's 3). This is the one where you had me worried about the hose pressure. But what this mode would do is to open the hose inlet but close off the seawater line that comes from the outdrive. So in this case, I would be pushing 100% fresh water from a hose towards the water pump, and ideally running the engine at the same time. It seems like this would work.... because the engine is running, the pump is moving, and because I've closed off the seawater inlet, I'm just flushing with pure fresh water into the pump so it's not diluted with sea water. This should be pushing MORE fresh water into my pump than would be present from running something like an alpha (with the impeller in the drive) on muffs, since I wouldnt be losing any water to leaking or losing any pressure in the muffs.

I think this fixes your concerns, is that correct? This seems like the best, most complete way to flush my engine, but please tell me if I'm wrong somehow! Thanks!

Lou C said:

I removed the plastic screen OMC put in the water intakes and I can rod out the holes in the lower unit with a piece of coat hanger wire by hanging off the swim platform. Had to do the same thing for my brother last summer. His 2020 Merc 4.5 started running hot & went into protection mode. Then I taught him the coat hanger wire trick!

Click to expand...

Haha awesome! Might have to try that trick (or something similar) at some point nice to know that's an option

If you do a standard oil analysis with Blackstone Labs or similar they will be able to tell you if your engine is wearing well and also if there are any contaminants in the oil like sodium, water, or fuel. With mine there were signs that the head gaskets were starting to leak way before the presence of water in the cylinders back in 2016. Knowing what I know now, as soon as I saw that I would have investigated repairs. I had an overheat in 2013 and it was OK for 2 more seasons and then water showed up in 2 cyls in August of 2016. I did the repairs that fall and spring and it's been fine since then. Here's an example of what the oil analysis shows:

Seeing as how your boat is in salt water all the time, I would be hauling it 2x a year, to clean out the water intake holes, inspect and replace anodes if needed, and re-apply antifouling paint (the paints for aluminum really don't last that long). You want to remove the outdrive once a season to make sure the driveshaft bellows isn't leaking, very important. Outdrive boats can be made to last in salt water but you must be diligent with maintenance. Of course if you see milky oil on the dipstick and under the valve cover then you know water is obviously getting in and it's time to take action. The other thing is the exhaust, most people would say to remove the elbows after 5 seasons to check them for corrosion as well as the exhaust manifolds, experience shows these parts last about 5-8 seasons in salt water, flushing them with something like the Neutra-Salt system will for sure help. I started scoping mine with a borescope camera, that way I can tell if the joint between the manifold & elbow is leaking. If you see rust stains on the outside of the joint then that's an obvious sign but you can have leaks inside with no sign outside.
Here's a couple pix, one has a bit of condensation from running at idle but neither shows a water leak around the joint....
The port side above runs cooler so that is condensation.
What I do is slide the rubber exhaust hoses down and then look inside with the camera, that way I don't have to take it all apart.
I also do a compression test at the end of each season.